Progress 10/01/09 to 09/30/14
Outputs
Target Audience: Teaching efforts in university undergraduate and graduate courses reached 65 students pursuing degrees in the Plant Scienes. Presentations made to local, regional, and national level garden and landscape nursery industry meetings allows current information being generated in our project regarding new woody plant cultivars and their performance to be utilized by attendees in their gardening and landscape nursery pursuits. Graduate students being advised in the project will become the next generation of industry professionals, teachers, and researchers in the landscape nursery industry. Three new woody landscape plant cultivars being released by the project will generate revenue at all levels of the supply chain for landscape plant production and sales. These new plants will add diversity to the options for cold hardy woody landscape cultivars for consumers. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Two graduate students are pursuing degrees in this project. Alex Susko is working towards completing a M.S. in Plant Breeding and Plant Molecular Genetics. His project involves the collection of Rhododendron viscosum, Swamp azalea within it's native range and evaluating the germplasm for adaptation to elevated pH soil conditions. Emily Ellingson is working towards completeing a M.S. in Plant Breeding and Plant Molecular Genetics. Her project involves a study of the conservation genetics of Minnesota's most endangered native tree species, Tsuga canadensis, Eastern hemlock. Three undergraduate students worked on research projects in our program. Mitchal Peterson completed an Undergraduate Researh Opportunities Program (UROP) project working on in-vitro seed germination protocol for rhododendron and azalea during the Spring semester, 2014. Elsa Eschenaur completed a Directed Studies project Spring semester 2014, working on developing protocols for in-vitro elevated pH tolerance screening protocols for rhododendrons and azaleas. Erin Pfarr completed an UROP project screeing three broad-leafed rhododendrons for elevated soil pH and carbonate levels in whole plant greenhouse studies in the Fall semester of 2014. All of these projects supported our effort to develop a robust high-throughput elevated pH and carbonate tolerance screening protocol for rhododendrons and azaleas. How have the results been disseminated to communities of interest? Oral presentations concerning research and cultivar development activities undertaken by our project were made at the local level; Minnesota Nursery Research Corporation, Minnesota Landscape Arboretum Employees, regional level; Southwest Research and Outreach Center Horticulture Days, Lamberton, MN; and national level; FarWest Nursery and Greenhouse Trade Show. Poster presentations were made at the American Society for Horticultural Science annual meeting; Aiello, A.S., J. Rothleutner, S. McNamara, and S.C. Hokanson. 2014. Mid-winter Cold Hardiness of Corylus fargesii Germplasm as Determined in Laboratory Freezing Tests. HortScience 48(9):S339; Susko, A., J.M. Bradeen, J. Friell, S. McNamara, and S.C. Hokanson. 2014. A need for speed: high through-put phenotyping for rhododendron pH adaptability. HortScience 48(9):S382 Two peer reviewed manuscripts were submitted and accepted for publication; Beier, G., S.C. Hokanson, S.T. Bates, and R.A. Blanchette. 2015. Aurantioporthe corni gen. et comb. nov., an endophyte and pathogen of Cornus alternifolia. Mycologia. 107:xxx-xxx and Hokanson, S.C., S. McNamara, K. Zuzek, M. Zins, and N. Rose. 2015. Wisteria frutescens, American wisteria, ‘Betty Matthews’ First Editions® Summer Cascade™. HortScience. What do you plan to do during the next reporting period to accomplish the goals? We will continue to make crosses between meritorious parents in various taxa in the breeding program. We will continue to evaluate seedling populations to identify advanced selections for extended evaluations. We will continue to evaluate and collect data on advanced selections of various taxa. If meritorious some will be entered into nursery and regional trials. We will continue to refine pH screening methodologies and utilize protocols to identify elevated pH and carbonate tolerant rhododendrons and azaleas. We will begin building rose populations to allow us to identify additional rose black spot resistance genes. We will continue lab and field based cold hardiness evaluations for various taxa. We will complete one more year of screening Corylus fargesii genotypes in collaboration with colleagues from the Morris and Morton Arboretums. We may undertake additional Rhododendron viscosum seed collections, dependant upon viability and germination rates for 2014 seed collections. We will collect additional Tusga canadensis seed from Minnesota, a Wisconsin population and a population from North Carolina to facilitate our population genetic analysis. We will submit a paper describing four rose cultivars released by the project. We will continue to give oral and poster presentations at local, regional, national, and international meetings as the opportunitie present themselves.
Impacts
What was accomplished under these goals?
Crosses were made in a number of woody plant taxa including deciduous azalea, weigela, hydrangea, and redbud. Seedling populations currently being evaluated include several maple species, buckeye hybrids, alder, birch, Ceanothus, katsura, eastern redbud, yellowwood, flowering quince, clethra, falsecypress, Turkish filbert, American smoketree, hydrangea, Tuliptree, and Spicebush Performance data are being collected on advanced selections from several taxa including; maple, birch, American smoketree, dogwood, katsura, common sweetshrub, clethra, flowering quince, sweetgum, crabapple, rose, elm, viburnum hybrids, and weigela. Cold hardiness screening was undertaken for several woody plant taxa were in the field and the laboratory. We continue to make good use of a snow-out-shelter developed and built at the North Central Research and Outreach Center in Grand Rapids, MN. Three year old seedlings can be heeled in under the shelter. Healing in prevents root freezing while the open sided shelter prevents snow accumulation that would protect the above ground portions of the plant from exposure to winter cold. Large numbers of plants can be evaluated in a relatively small space, with little labor investment, over the course of one winter. We sent seedlings from 24 taxa to Grand Rapids, MN to test for cold hardiness in the 'snow-out' shelter these include; several alder species, birch, spicebush, magnolia, crabapple, black gum, elderberry hybrids, and elm. Mid-winter laboratory cold hardiness tests were conducted on Corylus fargesii, oriental bittersweet genotypes, deciduous azaleas, katsura, yellowwood and alder. High throughput screening protocols for identifying rhododendrons and azaleas with elevated soil pH and carbonate tolerance were designed and tested. Initial results suggest genotype specificity for tolerance can be identified.
Publications
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2015
Citation:
Beier, G., S.C. Hokanson, S.T. Bates, and R.A. Blanchette. 2015. Aurantioporthe corni gen. et comb. nov., an endophyte and pathogen of Cornus alternifolia. Mycologia. 107:xxx-xxx.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Susko, A., J.M. Bradeen, J. Friell, S. McNamara, and S.C. Hokanson. 2014. A need for speed: high through-put phenotyping for rhododendron pH adaptability. HortScience 48(9):S382
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Teaching efforts in university undergraduate courses reached 54 students pursuing degrees in the landscape nursery industry. Presentations made to local, regional, and national level garden and landscape nursery industry meetings allows current information being generated in our project regarding new woody plant cultivars and their performance to be utilized by attendees in their gardening and landscape nursery pursuits. Graduate students being advised in the project will become the next generation of industry professionals, teachers, and researchers in the landscape nursery industry. Three new woody landscape plant cultivars being released by the project will generate revenue at all levels of the supply chain for landscape plant production and sales. These new plants will add diversity to the options for cold hardy woody landscape cultivars for consumers. Changes/Problems: The University of Minnesota will institute a service fee program for field research conducted on University farms and outreach stations. For long-generation woody crops these fees will be considerable. Our plants need to be sown in the greenhouse, transplanted several times over the course of 1-3 years before they go to the field. Evaluations take up to 10 years in the field. While in the field plants need to be irrigated, weeds need to be controlled, pruning needs to be done, and pests need to be controlled. Each of these services will need to be paid for. In order to meet anticipated costs, the number of projects we are undertaking will need to be cut back. What opportunities for training and professional development has the project provided? We provided an opportunity for an undergraduate student, Alex Susko, to complete a project funded by the University of Minnesota Undergraduate Research Opportunities Program. Alex wrote a grant proposal to the program that was funded and successfully completed the project. We hired Jacob Deaver, an undergraduate student, to assist with preparing wood samples collected from a biofuels project that is being finished up. Garrett Beier completed his M.S. degree this year and Ph.D candidate Will Kusch is currently writing his dissertation. How have the results been disseminated to communities of interest? Presentations at the 6th International Rosaceae Genomics Meeting, the VI International Symposium on Rose Research and Cultivation,63rd Annual Meeting of the IPPS Eastern Region, several local garden club and Master Gardner meetings. What do you plan to do during the next reporting period to accomplish the goals? Instituion of service fees at the University Field Stations may force us to cut back the breeding program. However, we will continue to make crosses, evaluate seedlings and collect data on advanced selections on the projects we carry forward. Work will begin on collecting and evaluating Rhododendron viscosum germplasm. We will undertake several laboratory-based cold hardiness screenings during the winter months of 2013-14.
Impacts
What was accomplished under these goals?
This year we released two deciduous azalea selections, UMNAZ 493 and UNNAZ 502. We are in the process of patenting them and have signed a marketing and distribution agreement with Bailey Nurseries for them. We are also releasing a Kentucky coffeetree selection, UMN 720283C. The tree will be distributed through non-exclusive license agreements with various North American nurseries.We have collected laboratory-based cold hardiness data in our lab in Excelsior, MN and field based cold hardiness data in Excelsior and Grand Rapids, MN. The data is collected for a wide range of woody plant taxa under evaluation in our program. We conducted some preliminary pH tolerance testing for rhododendron germplasm with an undergraduate student pursuing the work, funded by the University of Minnesota Undergraduate Research Opportunities Program. We culminated our investigations of the golden canker disease of Pagoda Dogwood. Results will be published in a submitted manuscript and one in preparation. Plans are currently being formulated to collect germplasm for the deciduous azalea species Rhododendron viscosum across its range of occurence in North America. This work will be carried out by a new PhD student in the program. The germplasm will be screened for various horticultural traits, most notably elevated pH tolerance and flooding tolerance.
Publications
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2012
Citation:
Bradeen, J.M., Luby, J., Hokanson, S.C., and Zlesak, D. 2012. The RosaR80 System: a framework for cross-species comparative analyses of R-genes from Rosaceous species. Rosaceae Genomics Meeting (Trento, Italy).
- Type:
Conference Papers and Presentations
Status:
Submitted
Year Published:
2013
Citation:
Bradeen, J.M., Zlesak, D., and Hokanson, S.C. 2013. Borrowing from neighbors: leveraging genome sequence of strawberry, apple, and peach to study disease resistance in rose. The VI International Symposium on Rose Research and Cultivation (Hannover, Germany).
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2013
Citation:
Hokanson,S.C., S. McNamara, K. Zuzek, N. Rose, and M. Zins. 2013. American wisteria (Wisteria frutescens (L.) Poir) 'Betty Mathews' First Editions R Summer Cascade TM wisteria. Poster. 63rd Annual Meeting of the IPPS Eastern Region. Chicago, Illinois.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2013
Citation:
Beier, G., S.C. Hokanson, and R.A. Blanchette. 2013. Aurantiadiaporthe corni gen. et comb. nov., an endophyte and pathogen of Cornus alternifolia. Submitted, Mycologia.
- Type:
Conference Papers and Presentations
Status:
Submitted
Year Published:
2013
Citation:
Zlesak, D., A. Clark, J. Bradeen, and S.C. Hokanson. Determining the association of scar marker ND5E and resistance to race 8 of Diplocarpon rosae Wolf in a diverse group of landscape roses. The VI International Symposium on Rose Research and Cultivation (Hannover, Germany).
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: Remaining advanced Shrub rose selections will be evaluated in a replicated trial to be planted in the spring of 2013. Shrub rose cultivar, Suddenly Summer, Summer Waltz, was released to the public in Summer 2012. Two new Deciduous azalea selections were approved for release and license agreements were signed with Bailey Nurseries. The two azaleas are in the process of being patented. Kentucky wisteria cultivar First Editions Summer Cascade was available for sale in the summer of 2012. Bailey Nurseries.has signed an exclusive license for the cultivar. We are evaluating 141 Weigela selections in replicated plots. An additional 2300 Weigela seedlings were planted in the field for evaluation. A trial site was established in Ames, Iowa to test F1 hybrid selections of Eastern Redbud. We continue to evaluate Korean Maple seedlings in field trials for cold hardiness and horticultural characteristics. We are currently evaluating Yellowwood seedlings which originated from trees growing in the upper Midwest. Five Katsura trees from evaluations at a USDA Plant Hardiness Zone 3b trial site in Grand Rapids, Minnesota were selected. Bailey Nurseries is conducting propagation trials on the selections. We made 12 selections of Flowering quince from seed collected from plants growing in Southwestern Michigan and Minnesota. Controlled crosses were made among these selections in 2012. A replicated field trial of 16 Cornelian cherry dogwood selections was established in 2011 with the objective of identifying individuals with more cold hardiness and superior floral, foliar, and fruiting characteristics. Additional field trials involve evaluations for cold tolerance, growth rates, and ornamental attributes of a number of shrub taxa including Boxwood, Beautyberry, New Jersey tea, Spicebush, Hornbeam maple, European black alder, Turkish hazel, Shingle oak, Royal azalea, and Japanese stewartia. We are conducting experiments to determine the efficacy of molecular markers linked to two rose black spot resistance genes for identifying resistant rose genotypes (marker assisted selection). We are concluding a series of experiments to understand golden canker disease of Pagoda dogwood. Development of cankers in inoculated seedlings is slow and unconducive to the screening of large amounts of germplasm for resistance. The fungal pathogen (Cryptodiaporthe corni) has been found to exist as an endophyte in non symptomatic trees which could facilitate spread of the disease. A phylogenic analysis of sequence data suggests that Cryptodiaporthe corni represents a new genus within the Cryphonectriaceae family. We are analyzing data collected over four seasons from alder plantings established in five sites in Minnesota. Three species, Alnus glutinosa, A. incana, and A. viridis exceeded 90% survival at all five sites and produced significantly more aboveground biomass than the other Alnus species. On a low-nitrogen site with coarse sandy soils, the three Alder species biomass production exceeded that of all other materials in the trial including commercially available poplar and willow selections. PARTICIPANTS: INDIVIDUALS: Steve McNamara - Project Scientist, Kathy Zuzek - UMN Horticultural Extension Specialist. PARTNER ORGANIZATIONS: Bailey Nurseries, Inc., Briggs Nursery, Inc., Conard-Pyle Nursery Company, Rosebay Nursery, Spring Meadow Nursery. COLLABORATORS: Dr. James Bradeen, UMN Plant Pathology, Dr. Thomas Debener, Leibniz Univ., Dr. David Zlesak, University of Wisconsin - River Falls, Dr. William Graves, Iowa State University Dr. Stephen Krebs, Dir. David Leach Research Station, Holden Arboretum, Dr. Timothy Rinehart, USDA-ARS, Poplarville, MS, Dr. Robert Blanchette, UMN Plant Path., Dr. Jennifer Juzwik, USDA Forest Service, Dr. Ulrike Tischner, UMN Dept. Bioproducts, Bioprocess Eng., Dr. Andrew David, UMN Dept. Forest Resources, Dr. Dean Current, UMN Dept. Forest Resources. TRAINING OR PROFESSIONAL DEVELOPMENT: Will Kusch, PhD candidate, Garrett Beier, MS candidate, Alex Susko, Undergraduate student, Jacob Deaver, Undergraduate student TARGET AUDIENCES: The target audience for woody landscape plant breeding efforts at the University of Minnesota is the landscape nursery industry in USDA Plant Hardiness Zones 3/4. Plants developed through our efforts are typically marketed for consumers in USDA Plant Hardiness Zone 3/4 locations. Genetic and physiological information generated by the project is directly utilized in our own breeding efforts. The information is also disseminated in peer-reviewed manuscripts, trade journals and through talks and poster presentations delivered at local, regional, national and international venues to academic, professional and lay audiences. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Our most recent rose release, Suddenly Summer, Summer Waltz represents a novel marketing and cultivar release strategy for the project. The cultivar, which has been a top performer in our trials for a decade, did not attract a private sector license partner. We decided to experiment with an in-house marketing/sales campaign that included a naming contest for University of Minnesota Landscape Arboretum members. Plants were sold exclusively at the Arboretum's annual plant sale Our two most recent deciduous azalea cultivar releases, UMNAZ 493 and 502 represent the first double-flowered and red flowering deciduous azalea cultivars with documented hardiness for USDA Plant Hardiness Zone 4 landscapes. Our Weigela breeding efforts are targeted toward developing reliably hardy, small statured plants with improved flower and foliage colors. Development of molecular markers tightly linked to rose black spot resistance genes will allow for fast, accurate selection of parents with resistance to specific races of rose black spot for breeding purposes. This will facilitate pyramiding of resistance genes into cultivars for durable resistance to rose black spot disease. The markers will also be used for selecting resistant seedlings in breeding programs. Refinement of the techniques should allow them to be used in private breeding programs as well. Our research of golden canker disease in Pagoda dogwood has led to an understanding that the disease can exist in a dormant endophytic state in nursery stock. In addition, poor pruning practice can lead to rapid development of disease in landscape trees. Knowledge that Alnus glutinosa, A. incana, and A. viridis exceeded 90% survival at all five sites trial sites in Minnesota allows us to focus future biofuel research efforts on these three species of Alnus. That the three species out produced all other poplar and willow species in the trials on a low nutrient glacial sand site suggests that these nitrogen fixing species merit further investigation as biomass crops in northern, glaciated landscapes.
Publications
- Hokanson, S.C. and S. McNamara. 2012. Cant Always Get What We Want! Finding and Creating Cold for Hardiness Screening at the University of Minnesota. 2nd International Symposium on Woody Ornamentals of the Temperate Zone, Ghent, Belgium (abst.)
- Kusch, W., U. Tschirner,, S. McNamara, A. David, D. Current, S.C. Hokanson. 2012 An Evaluation of Alnus (Alder) Germplasm in Five Diverse Nonagricultural Environments in Minnesota (U.S.A.). 2nd International Symposium on Woody Ornamentals of the Temperate Zone, Ghent, Belgium (abst.)
- Beier, G., R. Blanchette, S.C. Hokanson. 2012. Cryptodiaporthe corni Wehm., a latent pathogen in asymptomatic stems of Pagoda Dogwood (Cornus alternifolia). American Society for Horticultural Science Annual Meeting, Miami, FL. (abst.)
- Bradeen, J.M., J. Luby, S.C. Hokanson, D. Zlesak. 2012. The RosaR80 system: A framework for cross-species comparative analyses of R-genes from rosaceous species. 6th Rosaceae Genomics Conference, Trentino, IT. (abst.)
- Hokanson, S.C. and S. McNamara. 2012. This beauty you want to behold! Callicarpa spp. (Beautyberry). The Scoop, Minnesota Nursery and Landscape Association.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Testing agreements were signed with Spring Meadows Nursery to evaluate two new deciduous azalea selections. Sixteen new weigela selections were made in 2011. Thirty-eight parents were crossed with a goal of producing hardy, compact plants with exceptional floral and foliar characteristics. Precocious weigela seedlings from 2010 seedling populations were identified and will be used to examine potential link between seedling precocity and repeat bloom trait in mature plants. The hardy MN Strain redbud (Cercis canadensis) was hybridized with non-hardy cultivars in an attempt to produce hardy genotypes with novel foliage/forms. Additional crosses were made between hardy Korean Maple (Acer pseudosieboldianum) and purple-leafed cultivars of Japanese maple (A. palmatum) to develop a cold hardy, purple-leafed maple selection. We are conducting experiments to determine the efficacy of molecular markers linked to two rose black spot resistance genes for identifying resistant rose genotypes (marker assisted selection). In a diverse collection of 70 rose cultivars, a SCAR marker linked to the resistance gene was present in all resistant genotypes. The marker was also found in a small number of susceptible genotypes. We are currently conducting sequencing experiments to determine the nature of these polymorphisms. We continue studying golden canker disease of Pagoda Dogwood (Cornus alternifolia) incited by the fungal pathogen Cryptodiaporthe corni. We have developed an inoculation protocol that reliably infects seedlings. We are in the process of testing a range of Cornus species to determine if they could serve as alternative hosts for the pathogen. We are utilizing sequence data to determine genetic diversity among isolates collected across the range of occurrence of the pathogen. We continue to evaluate 13 Alnus species in comparison to Salix and poplar hybrids and species in replicated plantings at 5 sites in MN. These taxa are being considered as possible sources of cellulosic derived ethanol. The trials are being conducted on land not generally used for commodity agriculture, i.e. water saturated; nutrient poor, marginal farm lands in USDA Zone 3 locations. We are measuring growth, survival, biomass accumulation, wood composition, i.e. carbohydrates vs. lignin, crystallinity index of cellulose and fiber length, enzymatic hydrolysis efficiency and fermentable sugar yield and correlations between measurements of the above traits in juvenile vs. mature tree samples. We conducted cold hardiness screening trials on seedling populations of approximately 30 different tree and shrub species via a combination of field trials at the HRC and the Grand Rapids ROC and controlled tests in a programmable freezer. Seedlings selected from these trials are being grown on for further evaluation. PARTICIPANTS: PARTICIPANTS: INDIVIDUALS: Steve McNamara - Project Scientist, Kathy Zuzek - UMN Horticultural Extension Specialist PARTNER ORGANIZATIONS: Bailey Nurseries, Inc., Briggs Nursery, Inc., Conard-Pyle Nursery Company, Rosebay Nursery, Spring Meadow Nursery COLLABORATORS: Dr. James Bradeen, UMN Plant Pathology, Dr. Thomas Debener, Leibniz Univ., Dr. Stephen Krebs, Dir. David Leach Research Station, Holden Arboretum, Dr. Robert Trigiano, Univ. TN, Dr. Timothy Rinehart, USDA-ARS, Poplarville, MS, Dr. Philip Wadl, University of TN, Dr. John Erwin, UMN Dept. Hort. Sci., Dr. Robert Blanchette, UMN Plant Path., Dr. Jennifer Juzwik, USDA Forest Service, Dr. Ulrike Tischner, UMN Dept. Bioproducts, Bioprocess Eng., Dr. Andrew David, UMN Dept. Forest Resources, Dr. Dean Current, UMN Dept. Forest Resources TRAINING OR PROFESSIONAL DEVELOPMENT: Laci High, MS candidate, Will Kusch, PhD candidate, Garrett Beier, MS candidate TARGET AUDIENCES: TARGET AUDIENCES: The target audience for woody landscape plant breeding efforts at the University of Minnesota is the landscape nursery industry in USDA Plant Hardiness Zones 3/4. Plants developed through our efforts are typically marketed for consumers in USDA Plant Hardiness Zone 3/4 locations. Genetic and physiological information generated by the project is directly utilized in our own breeding efforts. The information is also disseminated in peer-reviewed manuscripts, trade journals and through talks and poster presentations delivered at local, regional, national and international venues to academic, professional and lay audiences. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Our four recent rose cultivars Northern Accents Lena, Ole and Sven and Sigrid continue to sell well in retail nurseries in the upper Midwest. Data from Earth-Kind trials (low input growing conditions replicated in multiple sites in the U.S.) reveal them to be among the top performers in such conditions. Crosses, evaluations and selections of deciduous azalea and broad-leafed rhododendron in MN represent the most comprehensive effort to develop USDA Zone 4 hardy cultivars for the upper Midwestern U.S. landscape nursery industry. Our Weigela breeding efforts are targeted toward developing reliably hardy, small statured plants with improved flower and foliage colors. Development of molecular markers tightly linked to rose black spot resistance genes will allow for fast, accurate selection of parents with resistance to specific races of rose black spot for breeding purposes. The markers will also be used for selecting resistant seedlings in breeding programs. Refinement of the techniques should allow them to be used in private breeding programs as well. Efforts to develop a high-throughput screening protocol for identifying resistance to golden canker in Pagoda Dogwood should lead to the species becoming a more widely sold tree in the upper Midwestern landscape industry. A better understanding of the epidemiology of this disease will lead to best management practices in the nursery and landscape for the species.
Publications
- 1. Krebs, S.L., M.C. Long and S.C. Hokanson. 2011. A garden survey of powdery mildew disease on deciduous azalea species and cultivars. Journal American Rhododendron Society 65:90-97.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: We continue evaluation of rose seedlings remaining in the program. The Conard/Pyle Company continues to test 17 UMN rose selections in PA and CA under a testing agreement made in 2007. Crosses were made between twenty deciduous azalea parents with the intent of developing late season flowering, disease resistant azaleas. Approximately 20 extremely late flowering seedlings were selected as parents for further breeding efforts. Briggs Nursery continues to evaluate seven UMN azalea seedlings being evaluated under a testing agreement made in 2008. Thirty-nine Weigela parents were crossed with the intent of developing reliably cold hardy, small statured plants with improved flower and foliage colors. Twenty eight Weigela selections were made this year. We are conducting experiments to determine the efficacy of molecular markers linked to two rose black spot resistance genes for identifying resistant rose genotypes. In a diverse collection of 70 rose cultivars, a SCAR marker linked to the Rdr3 resistance gene was present in all Race 8 resistant genotypes. The marker was also found in a small number of Race 8 susceptible genotypes. We are currently conducting sequencing experiments to determine the nature of these polymorphisms. We continue to conduct a series of experiments designed to determine the nature of the by-passing trait (simultaneous vegetative and floral bud expansion that results in obscured flowering) in cold hardy, large-leafed rhododendron. Segregation in three seedling populations suggests a genetic basis for the phenomenon. However, environmental (day-length and cold damage) and physiological (auxins) effects strongly influence expression. We are studying golden canker disease of Pagoda Dogwood (Cornus alternifolia) incited by the fungal pathogen Cryptodiaporthe corni. Currently we have 55 isolates collected, 45 from MN and 10 collected from PA, MA, CT. The cultures will be used in experiments designed to develop a high throughput screening protocol to identify golden canker resistant Pagoda Dogwood seedlings. Six different inoculation protocols will be tested to identify a method that reliably infects susceptible seedlings. In addition are utilizing sequence data to determine genetic diversity among isolates collected across the range of occurrence of the pathogen. We continue to evaluate 14 Alnus species, 10 Salix species and hybrids and 4 hybrid poplars in replicated plantings at 5 sites in MN. These taxa are being considered as possible sources of cellulosic derived ethanol. The trials are being conducted on land not generally used for commodity agriculture, i.e. water saturated, nutrient poor glacial sands, USDA Zone 3 abandoned corn land, USDA Zone 3 mine tailings site, USDA Zone 2 abandon hay field. We are measuring growth, survival, biomass accumulation, wood composition, i.e. carbohydrates vs. lignin, crystallinity index of cellulose and fiber length, enzymatic hydrolysis efficiency and fermentable sugar yield and correlations between measurements of the above traits in juvenile vs. mature tree samples. The hardiest alders to date include Alnus glutinosa, A. incana, A. rugosa, A. japonica, A. tenuifolia. PARTICIPANTS: INDIVIDUALS: Steve McNamara - Project Scientist, Kathy Zuzek - UMN Horticultural Extension Specialist PARTNER ORGANIZATIONS: Bailey Nurseries, Inc., Briggs Nursery, Inc., Conard-Pyle Nursery Company, Rosebay Nursery COLLABORATORS: Dr. James Bradeen, UMN Plant Pathology, Dr. Thomas Debener, Leibniz Univ., Dr. Stephen Krebs, Dir. David Leach Research Station, Holden Arboretum, Dr. Robert Trigiana, Univ. TN, Dr. John Erwin, UMN Dept. Hort. Sci., Dr. Robert Blanchette, UMN Plant Path., Dr. Jennifer Juzwik, USDA Forest Service, Dr. Ulrike Tischner, UMN Dept. Bioproducts, Bioprocess Eng., Dr. Andrew David, UMN Dept. Forest Resources, Dr. Dean Current, UMN Dept. Forest Resources TRAINING OR PROFESSIONAL DEVELOPMENT: Laci High, MS candidate, Will Kusch, PhD candidate, Andrea Clark, MS candidate, Garrett Beier, MS candidate TARGET AUDIENCES: The target audience for woody landscape plant breeding efforts at the University of Minnesota is the landscape nursery industry in USDA Plant Hardiness Zones 3/4. Plants developed through our efforts are typically marketed for to consumers in USDA Plant Hardiness Zone 3/4 locations. Genetic and physiological information generated by the project is directly utilized in our own breeding efforts. The information is also disseminated in peer-reviewed manuscripts, trade journals and through talks and poster presentations delivered at local, regional, national and international venues to academic, professional and lay audiences. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Our three recent rose cultivars Northern Accents Lena, Ole and Sven continue to sell well in retail nurseries in the upper Midwest. Data from Earth-Kind trials (low input growing conditions replicated in multiple sites in the U.S.) reveal them to be among the top performers in such conditions. Northern Accents Sigrid, our newest release, marketed and sold by Bailey Nurseries, Inc. will be available in retail nurseries and garden centers for the first time this spring. Crosses, evaluations and selections of deciduous azalea and broad-leafed rhododendron in MN represent the most comprehensive effort to develop USDA Zone 4 hardy cultivars for the upper Midwestern U.S. landscape nursery industry. Our cold hardiness testing revealed several popular new Weigela cultivars developed in Europe are not reliably cold hardy in USDA Plant Hardiness Zone 4 locations. Our Weigela breeding efforts are targeted toward developing reliably hardy, small statured plants with improved flower and foliage colors. Development of molecular markers tightly linked to rose black spot resistance genes will allow for fast, accurate selection of parents with resistance to specific races of rose black spot for breeding purposes. The markers will also be used for selecting resistant seedlings in breeding programs. Refinement of the techniques should allow them to be used in private breeding programs as well. Efforts to develop a high-throughput screening protocol for identifying resistance to golden canker in Pagoda Dogwood should lead to the species becoming a more widely sold tree in the upper Midwestern landscape industry. A better understanding of the epidemiology of this disease will lead to best management practices in the nursery and landscape for the species.
Publications
- Zlesak, D.C., V.M. Whitaker, S. George, and S.C. Hokanson. 2010. Evaluation of roses from the Earth-Kind Trials: Black Spot Diplocarpon rosae Wolf Resistance and Ploidy. HortScience 45:1779-1787.
- Wadl, P.A., X. Wang, J.K. Moulton, S.C. Hokanson, J.A. Skinner, T.A. Rinehart, S.M. Reed, V.R. Pantalone and R.N. Trigiano. 2010. Transfer of Flowering and Kousa Dogwood Simple Sequence Repeats (SSRs) to Selected Cornus (Cornaceae) Species. American Journal of Horticultural Science 135:279-288.
- Meyer, M.H., S.C. Hokanson, S. Galatowitsch, and J.J. Luby. 2010. Public Gardens: Fulfilling the Universitys Research Mission. HortTechnology 20:522-527.
- Long, M.C., S.K. Krebs, and S.C. Hokanson. 2010. Field and Growth Chamber Evaluation of Powdery Mildew Disease on Deciduous Azaleas. HortScience 45:784-789.
- Whitaker, V.M., T. Debener, A.V. Roberts and S.C. Hokanson. 2010. Unified nomenclature for an international collection of Diplocarpon rosae: races and a standard host differential set. Plant Pathology 59:745-752.
- McNamara, S. and S.C. Hokanson. 2010. Cold Hardiness of Weigela (Weigela florida Bunge) Cultivars. Journal of Environmental Horticulture 28:35-40. Hokanson, S.C. 2010. Lights in the Land of 10,000 Lakes. Pgs. 22-32. In: Royal Horticultural Society Yearbook of Rhododendrons, Camellias, and Magnolias.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: We continue evaluation of rose seedlings remaining in the program. Eighteen advanced selections and a commercial standard are being evaluated in a regional trial at Morris, MN. We have signed a license with Bailey Nurseries, Inc. to market and sell UMNRosa 362, a red-flowered polyantha garden rose. The Conard/Pyle Company continues to test 17 UMN rose selections in Pennsylvania under a testing agreement made in 2007. They have identified two promising selections that will be evaluated in multiple locations in 2010. Five new azalea selections were made this spring. We signed a testing agreement w/ Briggs Nursery to test the propagability of seven UMN azalea selections. In addition, we signed a testing agreement with Briggs to evaluate a large-leaf rhododendron selection. We conducted experiments w/ two rhododendron cultivars Haaga (a by-passing type) and Catawbiense Album (a non-by-passing type) to determine the effect of dormancy and day length on expression of the by-passing trait. By-passing is the simultaneous break in dormancy of vegetative and floral shoots that results in obscuring of the flowers. We have completed a genetic analysis of resistance to three North American races of rose black spot disease. Race 9 resistance was inherited quantitatively. Race 3 and 8 resistances are single gene mediated. Race 3 resistance resides within the same resistance gene cluster as the previously described resistance gene, Rdr1. Race 8 resistance segregates independently and represents a new black spot resistance gene Rdr3. We have developed a SCAR marker that is linked to Rdr3 at 9.1 cm. We have characterized the inheritance of partial resistance to rose black spot disease in tetraploid and diploid rose populations. We have identified general combining ability for the components of partial resistance to rose black spot disease. This is the first assessment of combining ability to be carried out for partial resistance to rose black spot disease. We have standardized the nomenclature and race status for all the cultured/characterized rose black spot races reported around the world. The races are now housed in the UMN Mycological Collection and are available upon request. We designed a new host differential array amalgamated from members of the all previous tests which will allow us to continuously evaluate new resistance breaking strains of the disease. We are currently evaluating five replicated plantings of woody germplasm for potential as a source of cellulosic-derived ethanol. The plots are in Gheen, Grand Rapids, Wadena, Becker, and Chanhassen, MN. The primary species under consideration is Alnus or alder, species that are nitrogen-fixing woody plants capable of growing on water saturated soils and nutrient poor soils which have never been used for food production. Fourteen alder species are being compared to willow, poplar, and aspen species and selections for survival, biomass production, wood chemistry, and ethanol yield. PARTICIPANTS: PARTICIPANTS: Individuals Steve McNamara - Project Scientist, Kathy Zuzek - MN Horticultural Extension Specialist PARTNER ORGANIZATIONS: Minnesota Nursery and Landscape Association, J. Frank Schmidt Family Charitable Foundation, Bailey Nurseries, Inc., Briggs Nursery, Inc., Conard-Pyle Nursery Company, Holden Arboretum COLLABORATORS: Dr. James Bradeen, U of Minn. Plant Pathology, Dr. Stephen Krebs, Dir. David G. Leach Research Station, Holden Arboretum, Dr. John Erwin, U of Minn. Dept. Hort. Science, Dr. Jennifer Juzwik, USDA Forest Service, Dr. Robert Blanchette, U of Minn. Plant Pathology, Dr. Ulrike Tischner, U of Minn. Dept. of Bioproducts, Bioprocess Eng., Dr. Andrew David, U of Minn. Dept. Forest Resources, Dr. Dean Current, U of Minn. Dept. Forest Resources TRAINING OR PROFESSIONAL DEVELOPMENT: Vance Whitaker - PhD candidate, Laci High - MS candidate, Will Kusch - PhD candidate, Andrea Clark - MS candidate, Garrett Beier - MS candidate, Alex Clasen - Undergraduate Student Worker TARGET AUDIENCES: TARGET AUDIENCES: The target audience for woody landscape plant breeding efforts at the University of Minnesota is the landscape nursery industry in USDA Plant Hardiness Zones 3/4. Plants are typically marketed by upper Midwestern Landscape Nurseries for sale to consumers in the region. Genetic and physiological information generated by the project is directly utilized in our own breeding efforts, but is also disseminated in peer-reviewed manuscripts, trade journals and talks at local, regional, national, and international venues to academic and professional audiences. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Sales of our three previous rose cultivar releases, Northern Accents Lena, Ole, and Sven have increased in each of the last two years, far outstripping estimates. Our newest release is expected to generate a similar consumer response with limited retail sales expected to begin in 2011. New deciduous azalea selections being tested for commercial propagation and production by Briggs Nursery in Olympia, WA, including a double flowering and a red flowering selection represent the only deciduous azaleas of these types possessing USDA plant hardiness zone 4 cold hardiness. The few broad leafed rhododendron cultivars cold hardy enough to survive USDA plant hardiness zone 4 winters exhibit a phenomenon known as vegetative by-passing. These cultivars elongate vegetative shoots at the same time the flowers are opening, which obscures the flower display. Determining the cause of by-passing will allow our breeding project to develop cold hardy rhododendrons with good flower displays. Identifying new rose black spot resistance genes will allow rose breeders to develop roses with resistance to specific black spot races. Each new resistance gene identified will bring breeders closer to developing a rose with durable resistance to the world's worst landscape rose disease. Understanding the nature of partial resistance to rose black spot will allow breeders to begin the process of developing quantitative (multigene) resistance to the disease. Standardizing the nomenclature for the world's known black spot races will allow research groups around the world working on this pathosystem to collaborate effectively. It will also allow for much quicker recognition of new resistance breaking isolates of the pathogen.
Publications
- Whitaker, V.M. and S.C. Hokanson. 2009. Partial resistance to black spot disease in diploid and tetraploid roses: general combining ability and implications for breeding and selection. Euphytica 169:421-429.
- Whitaker, V.M., J.M. Bradeen, T. Debener, A. Biber and S.C. Hokanson. 2009. Rdr3, a novel locus conferring black spot disease resistance in rose: genetic analysis, LRR profiling, and SCAR marker development. Theoretical and Applied Genetics. DOI 10.1007/s00122-009-1177-0.
- Whitaker, V.M. 2009. Genetic Analyses of Black Spot Resistance in Rose. Ph.D. Dissertation, University of Minnestoa, Twin Cities.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Twenty-seven advanced selections from our deciduous azalea breeding project were planted in a replicated trial at the David G. Leach Research Station (Holden Arboretum) in Mentor, Ohio. Results from the trial will tell us how widely adapted the azaleas might be. A new graduate student was hired on the project to investigate the genetic and/or physiological factors that control flowering and vegetative growth on broad leaf rhododendrons in the spring. Broad leafed rhododendrons hardy in Minn. winters exhibit a simultaneous floral and vegetative flush which results in obscured flowers. We are currently evaluating an F2 generation of Weigela resulting from populations developed from large statured, cold hardy cultivars crossed with less hardy, dwarf, colored foliage cultivars. Many of the new dwarf cultivars are not reliably hardy in Minn. A current graduate student has identified a third rose black spot resistance gene that maps to a different location than the two previously described. This is the first rose black spot gene identified in North America. We initiated a new project designed to evaluate 14 species of Alnus in comparison to poplar, hybrid aspen, and several willow species and cultivars for growth and biomass productivity in several Minn. environments and for cellulosic ethanol yield. Alnus is capable of fixing nitrogen and growing in watered saturated soils and thus could be grown in soils not typically utilzed for traditional agricultural production. Received authorization from the U of MN Horticultural Varieties Release Committee to release a powdery mildew resistant Nannyberry Viburnum 'Homefree' or use in the landscape nursery industry. 'Homefree' is currently being propagated for commecial release. It will be marketed by the Minnesota Nursery Research Corporation. The first retail sales of MN Rosa 251, 215, and 320 polyantha garden roses commenced this spring. The roses are being marketed under an exclusive marketing license with Bailey Nurseries under the trademark names Northern Accents Sven, Lena, and Ole respectively. We are currently negotiating the licensing of another red flowered polyantha rose, MN Rosa 362. PARTICIPANTS: Individuals Steve McNamara - Project Scientist, Kathy Zuzek - Part-time Project Scientist Partner Organizations Minnesota Nursery and Landscape Association J. Frank Schmidt Family Charitable Foundation Bailey Nurseries, Inc. Briggs Nursery, Inc. Holden Arboretum Collaborators Dr. James Bradeen, U of Minn. Plant Pathology, Dr. Stephen Krebs, Dir. David G. Leach Research Station, Holden Arboretum, Dr. John Erwin, U of Minn. Dept. Hort. Science, Dr. Jennifer Juzwik, USDA Forest Service, Dr. Robert Blanchette, U of Minn. Plant Pathology, Dr. Ulrike Tischner, U of Minn. Dept. of Bioproducts, Bioprocess Eng., Dr. Andrew David, U of Minn. Dept. Forest Resources, Dr. Dean Current, U of Minn. Dept. Forest Resources Training of Professional Development Vance Whitaker - PhD candidate, Laci High - MS candidate, Will Kusch - PhD candidate, Brandi Miatke - Undergraduate Student Worker, Ryan Crowe - Undergraduate Student Worker, Amber Halberg - Undergraduate Student Worker TARGET AUDIENCES: The target audience for woody landscape plant breeding efforts at the University of Minnesota is the landscape nursery industry in USDA Plant Hardiness Zones 3/4. Plants are typically marketed by upper Midwestern Landscape Nurseries for sale to consumers in the region. Genetic and physiological information generated by the project is directly utilized in our own breeding efforts, but is also disseminated in peer-reviewed manuscripts, trade journals and talks at local, regional, national, and international venues to academic and professional audiences. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Broad leafed rhododendrons are one of the most popular garden plants in the world. Few cultivars are hardy in USDA plant hardiness zone 3/4 landscapes. Cultivars developed at the University of Helsinki in Finland, derived from Rhododendron brachycarpum subsp. tigeerstedtii have reliably hardy flower buds for Minn. and environs. However, in the Minn. environment vegetative and flower buds break simultaneously resulting in the flowers being obscured. Ongoing experiments have been designed to determine the genetic and/or physiological basis for the phenomenon. This understanding will allow for development of Zone 3/4 hardy rhododendrons with an unobscured flower display. Determination of the race structure for the rose black spot pathogen Diplocarpon rosae in North America has allowed for the identification of race specific black spot resistance genes in rose germplasm. The search for such resistance genes in collaboration with colleagues in the United Kingdom and Germany has led to the discovery of a previously unidentified black spot resistance gene tentatively called Rdf3. The gene maps to a location unlinked to the two black spot resistance genes mapped in Germany. Discovery of the gene along with the understanding of the race structure for the disease provides the opportunity for breeders to develop multiply resistant rose cultivars that will be durably resistant in the landscape. It has become clear that future energy strategies will necessitate the use of many sources of energy. To date, the primary plant target for cellulosic ethanol has been corn. Increased use of corn for ethanol has put serious upward pressure on commodity prices around the world. Other sources of cellulosic ethanol need to be explored. Species in the genus Alnus are capable of fixing nitrogen, hence, they can grow on nutrient poor soils. In addition, Alnus naturally occurs on wet margins. These are two landscapes that are not critical for food production. As such, Alnus could be an important source of cellulosic derived ethanol. Ongoing research will determine the productivity of fourteen Alnus species in USDA plant hardiness zone 2-4 landscapes and it's potential for ethanol yield in comparison with the more studied woody genera willow, poplar, and hybrid aspen. New cultivars are the lifeblood of the landscape nursery industry. Woody plant cultivars released from the University of Minn. Woody Landscape Plant Breeding project expand the palette of plants available for landscape use in cold climates of North America. The polyantha roses released by the project are the first Zone 3/4 hardy polyanthas available on the market. Their tolerance to rose black spot disease eliminates the need for fungicide use in the garden. Powedery mildew disease is nearly ubiquitous on Nannyberry viburnum. Powdery mildew resistant 'Homefree' provides a resistant form of this versatile native plant.
Publications
- Book chapter Whitaker, V.M. and S.C. Hokanson. 2008. Breeding Roses for Disease Resistance. In press, Plant Breeding Reviews.
- Abstracts Hokanson, S.C., V.M. Whitaker, and J.M. Bradeen. 2008. Characterization of the rose black spot pathogen and the hunt for resistance genes at the University of Minnesota. First International Rose Genomics Conference, Angers, France (oral).
- Zlesak, D.C., K. Zuzek, and S.C. Hokanson. 2008. A step towards deciphering the inheritance of dioecy in Rosa setigera Mich.: The identification of a dominant male sterility gene, RSMS1. First International Rose Genomics Conference, Angers, France (poster).
- Whitaker, V.M., S.C. Hokanson. 2008. The inheritance of race-specific black spot resistances in tetraploid roses. HortScience 43:1101.
- Whitaker, V.M., and S.C. Hokanson. 2008. Genetics of resistance to Diplocarpon rosae in tetraploid roses. Phytopathology 98:S170.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Rose seedlings and selections continue to be evaluated in the field with the intent of developing USDA Zone 3/4 hardy repeat blooming, disease resistant shrub rose cultivars. Rose seedling populations segregating for resistance to identified rose blackspot (Diplocarpon rosae) races are being analyzed to determine the mode of inheritance of the resistance. Molecular markers are being developed and screened to identify a subset that are linked to rose black spot resistance gene(s). Heritability estimates for partial resistance to black spot are being determined. Efforts continue to develop a high throughput disease screening protocol for inoculating Pagoda dogwood with golden canker (Cryptodiaporthe corni) with the intent of identifying seedlings resistant to the disease. Approximately 500 seedlings resulting from 12 maternal families of Ribes aureum var. villosum are being evaluated for disease resistance, cold hardiness, flower quality, and plant architecture in a field
trial. Populations derived from dwarf and pigmented foliage Weigela cultivars and selections are being evaluated for cold hardiness, size, and flower productivity in field plantings. Regional cold hardiness and nursery production trials continue at five sites for advanced selections of Acer, Buxus, Cotinus, Malus, Rhododendron, Weigela, and Rosa. A new collaborative project has been initiated to evaluate Alnus germplasm for potential use as a source of cellulosic ethanol.
PARTICIPANTS: Steve McNamara, Project Scientist Kathy Zuzek, Former Project Scientist Vance Whitaker, Ph.D. candidate Bailey Nurseries, Inc. Dr. James Bradeen, Assistant Professor, Dept. of Plant Pathology, Univ. of MN Dr. Jennifer Juzwik, USDA Forest Service, St. Paul, MN Dr. Andrew David, Associate Professor, Dept. of Forest Resources, Univ. of MN Dr. Ulrike Tschirner, Associate Professor, Dept. of Bioproducts and Biosystems Engineering, Univ. of MN Dr. Dean Current, Program Director for the Center for Integrated Natural Resources and Ag. Management, Univ. of MN
TARGET AUDIENCES: Development of improved woody landscape plant cultivars hardy to USDA Plant Hardiness Zones 3/4 provides a backbone for the upper midwest U.S. nursery and landscape industry. Knowledge of the genetic and/or physiological basis of traits such as cold hardiness, disease resistance, and other stress tolerances will improve the efficiency of breeding woody landscape plant cultivars. Such knowledge is also useful for the development of best management practices for nursery growers and the consumer. Evaluation of Alnus as a new source of cellulosic ethanol creates the potential of producing ethanol on land that has never been utilized for commodity agriculture. This would reduce the competition for land dedicated to food production.
PROJECT MODIFICATIONS: Evaluating woody plant germplasm for potential as a source of cellulosic ethanol is a major new research endeavor for our project.
Impacts
Three polyantha rose cultivars, Rosa Northern Accents Sven, Lena, and Ole, developed by the project have been named and were released to the public in 2007 under an exclusive licensing arrangement with Bailey Nurseries, Inc. The University has negotiated a license agreement with Bailey Nurseries, Inc. for the marketing and sales of a USDA Zone 4a hardy Kentucky wisteria cultivar released by the project. Four races of rose black spot disease (Diplocarpon rosae) have been identified from isolates collected in seventeen locations in eastern North America. The races are maintained in a virulent state in vitro and are available for use by the research community.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
Rose germplasm with high field tolerance to blackspot (Diplocarpon rosae) were crossed with cold hardy repeat blooming shrub rose cultivars, selections, and germplasm with the intent of developing USDA Zone 3/4 hardy repeat blooming, disease resistant shrub rose cultivars. Three polyantha rose cultivars developed by the project have been named and will be released to the public in 2007 under an exclusive licensing arrangment with Bailey Nurseries, Inc. Rose germplasm is currently being screened for the presence of blackspot resistance genes. Populations segregating for blackspot resistance will be analyzed to determine the mode of inheritance of the resistance. Efforts continue to develop a high throughput disease screening protocol for inoculating Pagoda dogwood with golden canker (Cryptodiaporthe corni) with the intent of identifying seedlings resistant to the disease. The University is currently negotiating a license agreement for the marketing and sales of a USDA
Zone 4a hardy Kentucky wisteria cultivar released by the project. Regional cold hardiness and nursery production trials continue at five sites for advanced selections of Acer, Buxus, Cotinus, Malus, Rhododendron, and Rosa.
Impacts
Development of improved woody landscape plant cultivars hardy to USDA Plant Hardiness Zones 3/4 provides a backbone for the Upper Midwest U.S. nursery and landscape industry. Knowledge of the genetic and/or physiological basis of traits such as cold hardiness, stress adaptation and disease resistance will improve the efficiency of developing woody landscape plants and expand the potential for incorporating useful traits into the new cultivars
Publications
- Whitaker, V.M., K. Zuzek, and S.C. Hokanson. 2006. Resistance of Twelve Rose Genotypes to Fourteen Isolates of Diplocarpon rosae Wolf (Rose Blackspot) Collected from Eastern North America. Plant Breeding. (Accepted for publication)
- Whitaker, V.M., K. Zuzek, J.M. Bradeen, and S. C. Hokanson. 2006. Culturing and long-term storage of virulent races of the rose blackspot pathogen, Diplocarpon rosae. Acta Hort. (In press)
- Zlesak, D.C., K. Zuzek, and S.C. Hokanson. 2006. Rose pollen viability over time at varying storage temperatures. Acta Hort. (In press)
- Zuzek, K. and S.C. Hokanson. 2006. Cultivar development of shrub roses at the University of Minnesota Horticultural Research Center. Acta Hort. (In press)
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Progress 01/01/05 to 12/31/05
Outputs
Rose genotypes with high field tolerance to blackspot in Minnesota were crossed with cold hardy repeat blooming shrub rose cultivars, selections, and germplasm from the University breeding project with the intent of developing USDA Zone 3/4 hardy, repeat blooming, disease resistant shrub rose cultivars. The University is in the final stages of negotiating an exclusive license for three polyantha rose cultivars developed by the project. Fourteen isolates of rose black spot collected from across eastern North America were differentiated into 5 distinct races in a physiological race test using 12 Rosa genotypes. A molecular diversity assessment of 50 black spot isolates collected across eastern North America using AFLPs revealed high levels of marker diversity. Little structuring of the diversity based on geographic origin or host origin could be detected. Additional canker samples from Pagoda dogwoods infected with Golden canker (Cryptodiaporthe corni) were collected in
Minnesota. Additional Pagoda dogwood seed collections were made in USDA Plant Hardiness Zone 2 and 4 locations in Minnesota. Cryptodiaporthe corni samples have been established in culture and work is ongoing to develop seedling inoculation/screening protocols useful for identifying Golden canker resistant Pagoda dogwood seedlings. Crosses of powdery mildew tolerant deciduous azaleas identified in previous research were made with cold hardy cultivars, selections, and germplasm from the University breeding project with the intent of developing more mildew resistant, cold hardy cultivars. Seven deciduous azalea selections were sent to a plant propagation nursery to evaluate commercial production potential. Regional cold hardiness and nursery production trials continue for advanced selections of Viburnum, Cotinus, Malus, Acer, and Rosa.
Impacts
Development of improved woody landscape plant cultivars hardy to USDA Plant Hardiness Zones 3/4 provides a backbone for the Upper Midwest U.S. nursery and landscape industry. Knowledge of the genetic and/or physiological basis of traits such as cold hardiness, stress adaptation and disease resistance will improve the efficiency of developing woody landscape plants and expand the potential for incorporating useful traits into the new cultivars
Publications
- Gardner, N. and S.C. Hokanson. 2005. Intersimple sequence repeat fingerprinting and genetic variation in a collection of Clematis cultivars and commercial germplasm. HortScience 40:1982-1987.
- Hokanson, S.C., S. McNamara, K. Zuzek, N. Rose, and H. Pellett. 2005. Rhododendron 'Candy Lights' and 'Lilac Lights'. HortScience 40:1925-1927.
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Progress 01/01/04 to 12/31/04
Outputs
Rose genotypes with high field tolerance to blackspot in Minnesota were crossed with cold hardy, repeat blooming shrub rose cultivars, selections, and germplasm from the University breeding project for the purpose of developing USDA Zone 3/4 hardy, repeat blooming, disease resistant shrub rose cultivars. Fifteen advanced rose selections continue to be evaluated in a Zone 3b Minnesota trial and at 7 locations in North America. Three advanced selections are being propagated for release in 2007. Black spot (Diplocarpon rosae) isolates have been collected from across eastern North America. The isolates have been cultured on artifical media and placed into long-term storage. An ongoing experiment is designed to determine the rate of loss of virulence of the isolates over time in various storage treatments. Work has commenced to determine molecular diversity amongst the black spot isolates using Amplified Fragment Length Polymorphism (AFLP) markers. An array of rose
genotypes will be challenged with the isolates to determine race specificity for the pathogen. Five deciduous azalea selections were numbered and are currently being propagated for entry into advanced regional trials. Three seasons of field data concerning powdery mildew susceptibility/resistance for 41 deciduous azalea cultivars evaluated in MN and OH are being summarized into manuscript form. Seven genotypes did not show powdery mildew symptoms for the three seasons in either field location. A growth chamber evaluation of 23 of the genotypes evaluated in the field experiments revealed good correlations with field results, r=0.74. However, no genotypes showed complete resistance in the growth chamber. Stunted, chlorotic growth patterns exhibited by River birch seedlings grown in artificial soil media referred to as Birch Abnormal Growth Syndrome (BAGS) were found to be aleviated with foliar applications of nickle. Results of the experiments are being summarized in a manusript form.
Diseased branches from Pagoda dogwood trees exhibiting symptoms of Cryptodiaporthe canker were collected from various locations in MN. Fungal spores were isolated from the samples and cultured on artificial media. Morphological characters match those described for Cryptodiaporthe. Seed collections have been made from native populations of Pagoda dogwood in USDA Zone 3 and 4 locations in Minnesota. Seedlings derived from these collections will be inoculated with conidal suspensions collected from the cultured Cryptodiaporthe in an effort to identify seedlings resistant to the canker disease. Advanced selections of Acer saccharum, A. rubrum, and A. xfreemanii were planted in two tree production nurseries in MN and in a USDA Zone 3b cold hardiness trial in Grand Rapids, MN. Evaluation of growth characteristics of the selections in nursery conditions compared to industry standards will allow a determination as to whether the trees will be commercially acceptable/produceable by the
landscape nursery industry. Regional cold hardiness trials at the USDA Zone 3b site in Grand Rapids, MN continue for advanced selections of Viburnum lentago, Cotinus obovatus, Malus ssp., Acer species, and shrub rose selections.
Impacts
Development of improved woody landscape plant cultivars hardy to USDA Plant Hardiness Zones 3/4 provides a backbone for a 2.1 billion dollar Minnesota Nursery and Landscape Industry. Knowledge of the genetic basis for traits such as cold hardiness, stress adaptation, disease resistance, and the development of molecular markers will improve the efficiency of developing woody landscape plant materials and expand the potential for incorporating useful traits and characters into new cultivars.
Publications
- Long, M.C., S.L. Krebs, and S.C. Hokanson. 2004. Susceptibility of deciduous azalea cultivars to powdery mildew disease. HortScience 39:773.
- McNamara, S., K. Zuzek, N. Rose, H. Pellett, and S.C. Hokanson. 2005. FirefallTM Freeman Maple. HortScience 40:xxx-xxx.
- McNamara, S., K. Zuzek, N. Rose, H. Pellett, and S.C. Hokanson. 2004. FirefallTM Freeman Maple. Proceedings of the 13th METRIA Conference. http://www.ces.ncsu.edu/fletcher/programs/nursery/metria/metria13/
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Progress 01/01/03 to 12/31/03
Outputs
Rose selections showing high field tolerance to blackspot in Minnesota were crossed with cold hardy, repeat blooming shrub rose cultivars and advanced selections from the University breeding project for the purpose of developing USDA Zone 4 hardy, repeat blooming, black spot resistant shrub rose cultivars. An agreement was signed with Bailey Nurseries, Inc., St. Paul, MN to test 15 University of Minnesota advanced rose selections in 13 Bailey Nurseries trial locations in North America to determine suitability of selections for release as cultivars. Research was initiated to characterize pathogenic isolates of Diplocarpon rosae collected from across eastern North America. An array of rose genotypes will be challenged with the isolates to determine race specificity in the pathogen. Isolates will also be subjected to DNA fingerprinting analysis to determine molecular diversity in the organism. Crosses were made between late flowering genotypes of deciduous azalea species
Rhododendron viscosum, R. luteum and several cold hardy deciduous azalea in an effort to develop later flowering genotypes with Zone 3/4 cold hardiness and improved powdery mildew resistance. Powdery mildew susceptibility/resistance data was collected for a second year in replicated trials of 41 deciduous azalea cultivars planted in MN and OH. Data will be collected in 2004 and results will be summarized. Seedlings from reciprocal crosses of dwarf by full sized Weigela cultivars were evaluated for early developmental characters correlating to dwarf status with a goal to improve selection efficiency for dwarf plants. Within the same populations, selections are being made for Zone 4 hardy, dwarf Weigela genotypes with various leaf and flower colors. Inter Simple Sequence Repeat markers (ISSR) genetic fingerprints were developed for 31 vining Clematis species and cultivars. A single ISSR primer was sufficient to differentiate between five shrubby clematis species. The markers were
capable of distinguishing true hybrids from progenies with ambiguous morphologies. Genetic relatedness and clustering analysis utilizing the marker data did not reveal meaningful relationships between the genotypes evaluated in the study. Investigations designed to determine the cause of Birch Abnormal Growth Syndrome (BAGS), the stunted, cholorotic growth pattern exhibited by Betuala nigra seedlings grown in artificial soil media, continue. Current experiments are focusing on the potential role of various micronutrients in preventing the syndrome. Advanced selections of Acer saccharium, A. rubrum, and A. x freemanii have been propagated for Spring 2004 planting in three tree production nurseries in Minnesota and Michigan. Evaluation of growth characteristics of the selections in comparison to industry standards will allow us to determine whether the trees can be commercially produced for the landscape/nursery industry. Initiated Minnesota regional trials for advanced selections of
Viburnum lentago, Cotinus obovatus, Malus sp., Acer saccharum, A. rubrum, and A. x freemanii to determine the suitability of the selections as landscape plant cultivars in Minnesota Zone 3/4 locations.
Impacts
Development of improved woody landscape plant cultivars hardy to USDA Plant Hardiness Zones 3/4 provides a backbone for a 2.1 billion dollar Minnesota Nursery and Landscape Industry. Knowledge of the genetic basis for traits such as cold hardiness, stress adaptation, disease resistance, and the development of molecular markers will improve the efficiency of developing woody landscape plant materials and expand the potential for incorporating useful traits and characters into new cultivars.
Publications
- McNamara, S., Pellett, H., Rosen, C., and S.C. Hokanson. 2003. Abnormal growth of containerized River Birch (Betula nigra L.) seedlings growing in peat-based medium. HortScience 38:670.
- Gardner, N., Pellett, H. and S.C. Hokanson. 2003. Hybrid verification and fingerprinting using Inter-Simple Sequence Repeat (ISSR) primers in Clematis HortScience 38:667-668.
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Progress 01/01/02 to 12/31/02
Outputs
Rose hybridizations were made for the purpose of developing USDA Zone 4 hardy shrub roses with black spot resistance. Selections were made from 2000/01 rose seedling populations. A regional trial for 6 advanced shrub rose and 9 polyantha rose selections in three Minnesota locations and with collaborators at several North American sites is being initiated. Information from these trials will allow final cultivar release decisions for these selections. A project to screen a collection of deciduous azalea cultivars for powdery mildew resistance was initiated in two locations, Excelsior, MN and Madison, OH (partially funded by the American Rhododendron Society). Powdery mildew is a principle disease problem afflicting deciduous azaleas and is problematic for cold hardy germplasm developed by the University of Minnesota breeding program. Initial results suggest field resistance exists in cultivated material, although quantifiable results are not expected until the end of
the 2004 field season. A parallel survey of arboretum plantings (Holden, Madison, OH; Seacrest, Wooster, OH; Dawes, Newark, OH) suggests North American deciduous azalea species are highly resistant to infection. Inter Simple Sequence Repeat molecular markers are being developed to fingerprint cultivars of Clematis and Wisteria and verify hybrid status of Clematis seedlings arising from a inter-specific breeding project (in collaboration with Dr. Harold Pellett, Landscape Plant Development Center). A project to identify populations, collect seed and evaluate seedling populations of several small statured, shade tolerant native tree species with landscape plant potential, including Acer pensylvanicum, Carpinus caroliniana, Cornus alternifolia, Tsuga canadensis, and Cercis canadensis has been initiated. Identification of cold hardy seedlings with landscape potential will expand the offering of plants available for use in the the upper Midwestern U.S. Cooperative relationships with
several tree production nurseries in Minnesota and the upper Midwest to evaluate advanced selections of shade trees for nursery/production characteristics are being developed. Regardless of landscape merits, if a tree does not perform well in the production nursery, it will never reach the market. Information from these trials will allow for an apraisal of the nursery production capabilities of advanced tree selections from the breeding program. An investigation of birch abnormal growth syndrome (BAGS)is being concluded. River birch seedlings exhibit abnormal growth (contorted, chlorotic, stunted leaves) when germinated and grown in artificial soil mixes. Symptoms are alleviated with the addition of sterilized birch forest soil. Soil and tissue analysis results should help determine variables that exist in artificial soil mixes which cause the syndrome. Commercially availiable Summersweet Clethra cultivars are being evaluated for cold hardiness. Although often said to be USDA Zone 4
hardy, knowledge of Clethra cold hardiness is largely anectodal, based on the range of distribution of the native species. Results from this evaluation will provide definitive information on Clethra cultivar cold hardiness.
Impacts
Development of improved woody landscape plant cultivars hardy to USDA Plant Hardiness Zones 3/4 provides a backbone for a 2.1 billion dollar Minnesota Nursery and Landscape Industry. Knowledge of the genetic basis for traits such as cold hardiness, stress adaptation and the development of molecular markers will speed the process of developing woody landscape plant materials and expand the potential for incorporating useful traits and characters into new cultivars.
Publications
- McNamara, S., Pellett, H., Florkowska, M. and Lindstrom, O., Jr. 2002. Comparison of the cold hardiness of landscape tree and shrub cultivars growing at two disparate geographic locations. J. Environ. Hort. 20:77-81.
- Rose, N., McNamara, S., Pellett, H., and Zuzek, K. 2002. Rhododendron 'Mandarin Lights', 'Lemon Lights', and R. 'Tri-Lights'. J. Environ. Hort. 20:62-63.
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Progress 01/01/01 to 12/31/01
Outputs
Breeding efforts were continued with shrub roses, deciduous azaleas, viburnums, Mountain Ash, Freeman maples, etc. Additional crosses of roses and azaleas were made. Much of the effort in 2001 was devoted to evaluation of existing hybrid progeny. We have many selections of red flowered azaleas that look very promising. Cold winter weather is needed to aid in screening for cold tolerance. Laboratory hardiness screening is being utilized to aid in narrowing the selections for further evaluation. Selections of Maackia, Sorbus, Acer Freemanni, Cornus and Rhododendron were approved for introduction. A mildew resistant selection of Viburnum lentago and selections of Staphylea trifoliata look promising. Studies to improve techniques for evaluation of tolerance to drought, poorly drained soils and high pH soils are continuing. Efforts to select cold hardy seedlings of plant species that are marginal in hardiness are also continuing. Recent mild winters has hampered the
success of this effort. Stan Hokanson took over leadership of the project in July.
Impacts
New plants are widely accepted by the gardening public and increase the total income from production and sales of nursery stock. A broader choice of plants well adapted to local growing conditions contribute to improved landscapes and increase the value and environments of our homes and cities.
Publications
- McNamara, Steve and Harold Pellett. 2001. Effect of High pH on Foliar Chlorosis and Growth of Five Betula Species. J. Environ. Hort. 19(4):175-179.
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Progress 01/01/00 to 12/31/00
Outputs
Breeding efforts were continued with deciduous azaleas, shrub roses, and Viburnum. Interspecific hybridization between Acer rubrum and Acer saccharinum, and intergeneric Hybridization between Sorbus and related genera, were also continued. Additional selections of each group were propagated for further evaluation. A number of very promising selections of shrub roses are now available. Recent mild winters has made evaluation of cold hardiness difficult. Current breeding emphasis with azalea is for development of mildew resistant plants and selection of cultivars with red flowers. Rose and azalea selections are being evaluated for cold hardiness by laboratory procedures to supplement field observations. A selection of azalea with intense lavender-purple flower color has been chosen for introduction as an improvement over Orchid Lights. A selection of Cornus hessei with chartreuse foliage color, and interspecific hybrid selections of Sorbus alnifolia X Sorbus aucuparia
and Acer saccharinum X A. rubrum, have been deemed ready for introduction. We are continuing research to improve techniques to screen for tolerance to high soil pH levels. Paddies developed for wild rice breeding are being used to select for tolerance of woody plants to poorly drained soils. Following establishment of plantings, the paddies are flooded and plants allowed to undergo stress. The paddies are then drained and the more tolerant plants are selected and allowed to recover. Visual symptoms of injury and changes in photosynthetic rate are being used to estimate tolerance to the flooded conditions.
Impacts
New plants are highly sought by the gardening public and increase the total income from production and retail sales of nursery stock. A broader choice of plants that are well adapted to the local growing conditions contribute immensely to the environment of our homes and cities.
Publications
- McNamara, Steve and Harold Pellett. 2000. Cold Hardiness of Phellodencron sachalinense Friedr. Schmidt Seedlings Increases with Age. HortScience 35(2):
- Pellett, Harold. 2000. Developing New Woody Landscape Plants. The International Plant Propagators' Society, Combined Proceedings:49: 337-339.
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Progress 01/01/99 to 12/31/99
Outputs
Breeding efforts were continued with deciduous azaleas, shrub roses, and Viburnum. Interspecific hybridization between Acer rubrum and Acer saccharinum, and intergeneric hybridization between Sorbus and related genera were also continued. Additional selections of each group were made and propagated for further evaluation. Current breeding emphasis with azalea is for development of mildew resistant plants and selection of cultivars with red flowers. A selection of Maackia amurensis and a pink flowered, mildew resistant azalea selection have been targeted for introduction. Cooperative effort with the University of Georgia to compare cold hardiness of the same cultivars on the same dates at the two sites was concluded. We are continuing research to improve techniques to screen for tolerance to high soil pH levels, utilizing potted plants with artificial soil mix. Reduction of media oxygen content has been necessary to impose chlorotic symptoms. A large scale procedure to
screen for tolerance to poorly drained soils is being used to compare tolerance of a number of woody plants. Following establishment of plantings in wild rice patties, the paddies are flooded and plants allowed to undergo severe stress. After considerable stress has been imposed, the paddies are drained, and the more tolerant plants are selected and allowed to recover. Visual symptoms of injury and changes in photosynthetic rate are being used to estimate tolerance to the flooded conditions.
Impacts
New improved plants developed through this project add potential for creating better landscapes and provide additional inventory for Minnesota nurseries and garden centers to produce and sell, adding to the state economy. For example, over a quarter of a million plants of our azalea introductions were sold in 1999.
Publications
- McNamara, Steve and Harold Pellett. 1999. Cold Hardiness of Phellodencron sachalinense Friedr. Schmidt Seedlings Increases with Age. (accepted for publication) HortScience 35(2):
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Progress 01/01/98 to 12/31/98
Outputs
Study to determine cold hardiness of selected taxa on the same date on different years was concluded. Hardiness differed somewhat from year to year but there were not consistent trends across cultivars that related to differences in weather conditions. In a cooperative study with the University of Georgia, we are comparing cold hardiness of selected plant taxa growing at both sites on the same dates. On Sept. 22, plants had nearly equal hardiness while Minnesota plants increased in hardiness much more rapidly in later dates. Breeding efforts were continued with azaleas, shrub roses, Sorbus, Viburnum, Pyrus,and Acer. Rose crosses in 1998 emphasized use of species by cultivar hybrids as parents. Sixty new selections of roses were made for further evaluation or use as parents. Seedlings were grown from 34 rose species accessions collected in Kazakhstan and from 96 accessions from China. Evaluation of roses introduced by Dr. Griffith Buck has been completed and data is
now being analyzed for publication. We are initiating a new evaluation effort with groundcover and patio roses. An evaluation plot has been established with most of the more recent Amelanchier cultivars now available. Evaluation of crabapple and shade tree cultivars is continuing with new cultivars added each year. A field planting has been established to evaluate tolerance of woody plants to poor drainage. We are using a plot surrounded by a berm with an interior drainage ditch that can be closed or open. Plants established in 1998 will be flooded in 1999 for a controlled period of time.
Impacts
(N/A)
Publications
- McNamara, Steve and Harold Pellett. 1998. Cold Hardiness of Weigela Cultivars. J. Environ. Hort. 16(4):238-242.
- McNamara, Steve. 1998. Effect of Soil pH on Betula sp. Landscape Plant News. 9(no 3):14-15
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Progress 01/01/97 to 12/31/97
Outputs
Breeding emphasis to develop cold hardy, red flowered deciduous azaleas continued. 12 new selections were made for further evaluation. Shrub rose crossing in 1997 emphasized use of polyantha roses as one parent. Conditions favoring heavy infestation of black spot enabled heavy roguing of susceptible offspring. Pyrus interspecific hybrids in the Landscape Plant Development Center's cooperative program began flowering. All plants that flowered in 1997 had P. fauriei as one of their parents. Tissue cultures of Lonicera, Malus, and Syringa were treated with colchicine and oryzaline to induce tetraploids. Study was continued to determine hardiness level of selected taxa on the same date over many years. Cooperative study with the University of Georgia was initiated to compare cold hardiness levels on the same dates of selected plant taxa growing at both sites. Comparison of five Betula species for relative tolerance of high soil pH found B. Alleghaniensis to be more
tolerant than B. nigra, B. papyrifera, B. lenta and B. platyphylla. Acer Xfreemanii 'Autumn Blaze' was found to be more drought tolerant than Acer rubrum cultivars tested. A portable freezing unit was used to freeze seedlings growing in an outdoor seedbed in January. A few surviving plants each of Xanthoceras sorbifolium, Cornus florida, Cornus mas, Pterostyrax hispida, Styrax japonica and Syringa pekinensis were selected for further evaluation. Many different taxa of trees and shrubs were planted in various typical landscape situations for evaluation of adaptability under different growing conditions.
Impacts
(N/A)
Publications
- PELLETT, H. 1997. The Landscape Plant Development Center Past, Present and Future. Proceedings of the Symposium on Landscape Plants Exploration, Breeding, Evaluation. June 27-29, 1996 Sponsored by the Landscape Plant Development Center, P.O. Box 39, Chanhassen, MN 55317 pp.5-9.
- PELLETT, H. 1997. Breeding of Cold Hardy Woody Landscape Plants in the upper Midwest. In pgs 317-323. In "Plant Cold Hardiness Molecular Biology, Biochemistry and Physiology". Paul Li and Tony Chen eds. Plenum Press, NY, London. 368p.
- PELLETT, H, R. HUMMEL AND S. WIEGREFE. 1997. Landscape Plant Development Center Breeding Programs. Proceedings of the Symposium on Landscape Plants Exploration, Breeding, Evaluation. June 27-29, 1996 Sponsored by the Landscape Plant Development Center, P.O. Box 39, Chanhassen, MN 55317 pp.5-9.
- VAINOLA, A., S. MCNAMARA AND H. PELLETT. 1997. Stem and Flower Bud Hardiness of Deciduous Azaleas. J. Environ, Hort. 15(1)45-50.
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Progress 01/01/96 to 12/30/96
Outputs
Cooperative efforts to evaluate new and promising woody landscape plants under city conditions were initiated with Hennepin County and the city of Mpls. Use of brownfields will have the added dimension of evaluating tolerance to soil contaminants and potential for bio-remediation. Breeding efforts with azaleas, shrub roses, Sorbus, Viburnum, Pyrus, Acer, were continued and breeding of Carpinus was initiated. Promising plants of Pyrus were propagated for further evaluation. Additional Sorbus and Viburnum were also selected. New selections of azaleas included many with excellent red flower color. A planting was established at Becker, MN, for evaluation of large leafed evergreen rhododendron seedlings. Tetraploid plants of Spiraea bumalda were obtained through treatment of tissue cultures with colchicine. These will be used in developing sterile cultivars. Flow cytometry was used to verify increased DNA content. Plants of Lonicera have been treated with spindle fibre
inhibiting chemicals to induce polyploidy. In cooperation with the U of GA-Griffin, plants of several taxa were established at both locations to initiate a study comparing the cold acclimation cycle as influenced by differences in climate. A portable freezing unit has been constructed to use in the field for screening seedlings for cold tolerance. It is being tested during the winter of 1996-97 for effectiveness in seedling screening. Procedures for screening for tolerance to high soil pH are being developed and utilized.
Impacts
(N/A)
Publications
- PELLETT, H. AND S. MCNAMARA. 1994. (Printed in 1996) Cold Hardiness of Crabappleand Pear Cultivars. Proceedings of the eighth conference of the Metropolitan Tree Improvement Alliance and the International Ornamental Crabapple Society. Metr.
- ZUZEK, K., M. RICHARDS, S. MCNAMARA AND H. PELLETT. 1996. Roses for the North - Performance of Shrub and Old Garden Roses at the Minnesota Landscape Arboretum. Minnesota Ag. Expt. Stat. Univ. of Minn. Minnesota Report 237-1995. 92pp.
- BERGMANN, B. A., W. P. HACKETT AND H. PELLETT. 1996. Somatic Embryogenesis in Aesculus. In Vitro Cell. Dev. Biol. -Plant 32:161-164.
- MCNAMARA, S. AND H. PELLETT. 1996. Cold Hardiness of Flowering Crabapple Cultivars. J. Environ. Hort. 14:111-114.
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Progress 01/01/95 to 12/30/95
Outputs
Breeding of deciduous azaleas continued. Many selections were made for additional evaluation. Additional evaluation sites planted including about 1000 plants in the Duluth area. A yellow flowered selection, #113, was named Lemon Lights. Efforts were also continued with hybrids of Acer rubrum, Philadelphus, Spiraea and integeric hybrids between Sorbus and related genera. Breeding of shrub roses continued. An additional planting of shrub rose cultivars was established to evaluate cold hardiness and disease resistance. Data on many characteristics has been compiled and published. Efforts to develop efficient, reliable systems for screening for tolerance to drought, soil compaction and high pH are continuing. Cold hardiness studies included determination of hardiness levels of Weigela cultivars throughout the winter season, comparison of hardiness levels of representative plants at the same date in different winters. Through efforts of the Landscape Plant Development
Center interspecific hybridization of maples was continued. Emphasis in 1995 was with species in the Palmata section. Successful crosses between Acer pseudosieboldiana and A. palmata and A. pseudosieboldiana and A. japonica were obtained. These were propagated by embryo excision. Hybridity will be verified with DNA analysis techniques. Embryo rescue techniques were utilized in an effort to obtain hybrids between different species of Viburnum and between different genera in the Pomoidaea subfamily of Rosacceae.
Impacts
(N/A)
Publications
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Progress 01/01/94 to 12/30/94
Outputs
DNA content of Rhododendron in sections Pentandra and Rhodora was determined by flow cytometry. DNA content of the various taxa fit into three groups. These correspond to 2X,3X, and 4X. In most cases the DNA content group is consistant with reported ploidy levels. However plants sampled of Rhododendron canadense,a reported tetraploid, fit in the 2X class for DNA content. Breeding of deciduous azaleas continued. Many promising selections survived the severe winter without flower bud injury. A yellow flowered selection, #113, will be proposed for introduction. Selection #43 has been named Mandarin Lights. Evaluation and selection efforts were also continued with hybrids of Acer rubrum, Philadelphus, Spiraea, and integeric hybrids between Sorbus and related genera. Breeding of shrub roses continued. An additional planting of shrub rose cultivars was established to evaluate cold hardiness and disease resistance. Data on cold hardiness, disease resistance, flowering
characteristics, and plant form has been compiled and prepared for publication as an Experiment Station bulletin. Efforts to develop efficient, reliable systems for screening for drought tolerance are continuing. A system is being developed to utilize dialysis bags with PEG to impose known constant levels of stress. Cold hardiness studies underway include determination of hardiness levels of Weigela cultivars throughout the winter season and comparison of hardiness levels of representative plants at the same date in different winters.
Impacts
(N/A)
Publications
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Progress 01/01/93 to 12/30/93
Outputs
Lonicera #14 was named Honey Rose. Exochorda serratifolia `Northern Pearls' and selections of Gymnocladus dioica and Phellodendron sachalinensis were approved for introduction. Additional crosses were made with Rhododendron, Rosa, Sorbus X Aronia hybrids, Acer rubrum and Acer rubrum X Acer saccharinum. Evaluations were continued with hybrids of these species and with Philadelphus, Forsythia, and Spiraea. We helped support a plant exploration trip to Russia. Seeds of 158 accessions of plants were acquired and will be evaluated. Cold hardiness evaluations of different taxa of Pyrus were concluded, and efforts with crabapple were continued. Efforts were also made to study the role of temperature regimes on rate of cold deacclimation. Efforts are underway to develop techniques for screening woody plants for drought tolerance. Relative drought tolerance of ten cultivars of Acer rubrum were determined. Through cooperative efforts of the Center for Development of Hardy
Landscape Plants (CDHLP), hybrids of Pyrus were planted at Washington, Minnesota, and Michigan. Interspecific crossing of Acer was explored using collections of the Morris, Arnold, Holden, and Morton Arboreta. Sex expression was determined and promising interspecific combinations were identified. Optimal storage conditions (15% R.H.;4(degree)C) for prolonged pollen viability in Amur maple were determined. These conditions extend the useful life of pollen to seven weeks.
Impacts
(N/A)
Publications
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Progress 01/01/92 to 12/30/92
Outputs
Breeding work was continued with deciduous azaleas, red maple, red X silver maple hybrids, Viburnum, Lonicera, Philadelphus, shrub roses, and Sorbus intergeneric hybrids. Azalea #43, Lonicera #14, and a dwarf Red Pine selection (in cooperation with University of Wisconsin) were approved for introduction. Cutting propagation of Aesculus `Autumn Splendor' was not satisfactory at any date of collection or propagation conditions. In cooperative research with Dr. William Graves (Department of Horticulture, Iowa State University), cuttings of individual plants of Maackia from the Washington, D.C. and Minnesota areas rooted successfully. Collection date had little influence, but differences occurred between individual plants in rooting success. Research to determine flower bud cold hardiness levels of cultivars of Forsythia at different times throughout the dormant season was concluded. Similar studies are in progress with cultivars of Pyrus calleryana and flowering
crabapple. Cooperative activities of the Center for Development of Hardy Landscape Plants continues to expand. Several institutions in the Scandinavian and Baltic countries have joined. Supporting membership in the Center is growing. Through the Center, breeding work was continued with Pyrus, and efforts were initiated with different groups of Acer using plants at the Morton Arboretum.
Impacts
(N/A)
Publications
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Progress 01/01/91 to 12/30/91
Outputs
Breeding efforts were continued with deciduous azaleas, shrub roses, red maple, honeysuckle, viburnum, mock orange, and intergeneric hybridization of Sorbus and Aronia. Hybridization of evergreen rhododendron was initiated. Through the Center for Development of Hardy Landscape Plants, a cooperative effort was initiated to develop small landscape trees of Pyrus. Selections of honeysuckle resistant to the witches broom aphid were further evaluated. One selection has been identified for possible introduction. Propagation was initiated to build up stock. Several promising selections were made from advanced generation populations of intergeneric hybrids between Sorbus and Aronia. They were propagated for more detailed evaluation. Several compact plants of Forsythia and Philadelphus have been identified from hybrid populations for further observation. Additional selections of deciduous azaleas, red maple, and viburnum were also identified and propagated for continued
evaluation. Cold hardiness research was also continued. Hardiness throughout the winter was ascertained for different taxa of shrub roses, forsythia, and Pyrus. Research has been initiated to evaluate acclimation and midwinter hardiness of cultivars of crabapples. Efforts are continuing to develop and improve screening techniques to determine tolerance of woody plants to drought and soil compaction. Some initial screening for tolerance to foliage water loss has been done with Acer, Tilia, and Pyrus.
Impacts
(N/A)
Publications
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Progress 01/01/90 to 12/30/90
Outputs
Breeding efforts were continued with deciduous azaleas, shrub roses, viburnums, red maple, honeysuckle, and intergeneric hybrids between Sorbus and other genera of the Pomoidae subfamily. Crosses between Viburnum carlesii and other species initially set fruit but abort prior to maturity. Embryo rescue may be useful in achieving successful crosses. Similar results were obtained with crosses between several Aesculus species. Evaluation was initiated in progeny from previous crosses in Forsythia and Philadelphus, A selection of Spiraea is being increased for likely introduction. Plants of our introduction, Acer rubrum 'Autumn Spire' were available through the nursery trade this year. Research to develop screening techniques for tolerance to soil compaction and drought are progressing. Measurements of rate of moisture loss by detached leaves looks like a promising technique for prediction of drought tolerance due to resistance to evapo-transpiration. Acer truncatum has
greater tolerance than A. platanoides, which in turn is more resistant than A. saccharum cultivars. Storage of pollen of Rosa and Rhododendron under different temperature regimes indicate that good viability can be maintained for at least 12 months by storage at -15 C. if frozen soon after adequately dried. The Center for the Development of Hardy Landscape Plants was established to increase research directed toward development of stress tolerant plants and to encourage cooperative efforts.
Impacts
(N/A)
Publications
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Progress 01/01/89 to 12/30/89
Outputs
Breeding was continued with Rhododendron, Lonicera, Viburnum, Acer, and Sorbus intergeneric hybrids. Second generation hybrids between Rhododendron viscosum and Exbury hybrids have good plant form, foliage and floral qualities, and mildew resistance. Many selections of Lonicera were made that combine resistance to the witches broom aphid with rosy flowers. Autumn Spire Red Maple will be available for sale in 1990 and a selections of Viburnum and another azalea have been released for production. Breeding of hardy shrub roses was initiated. Evaluation of many plant taxa for adaptability and landscape qualities continues. Evaluation of hardiness capability of shrub rose and forsythia taxa using lab procedures is underway. Studies to determine viability of pollen following storage under different conditions is underway. Grafting, root cutting, and tissue culture techniques are being evaluated to develop feasible means of propagation of Aesculus 'Autumn Splendor'. A
comparison of the acclimation of juvenile and adult forms of Hedera helix indicate that daylength has little influence on the acclimation. Cold temperature causes both forms to acclimate. Little difference exists in acclimation rate. Tests of current seasons growth indicate that stem tissue of mature plants of Cercis canadensis and Phellodendron sachalinense cold acclimate sooner than juvenile plants grown in the field. Research is underway to develop techniques for screening woody plants for tolerance to soil compaction and moisture stress.
Impacts
(N/A)
Publications
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Progress 01/01/88 to 12/30/88
Outputs
Breeding efforts with deciduous azaleas, viburnums, honeysuckle, red maple, and intergeneric hybrids between Sorbus and other members of the Pomoidae subfamily were continued. Many promising selections of honeysuckle were made for further evaluation that combine resistance to the witches broom aphid with rosy flower color. A concerted effort has been initiated to evaluate shrub roses for hardiness, repeat bloom, pest resitance and aesthetic qualities. Evaluation will include field performance and laboratory study of the acclimation process and maximum capacity to harden. Research is underway to compare ability of juvenile and adult plants of a single clone of Hedera helix to acclimate in response to environment stimuli. Initial results indicate that adult plants acclimate faster than juvenile plants. A second objective of the research is to determine potential for using leaf discs to study the acclimation process. Early results indicate that detached leaf discs
can be induced to acclimate however they are slower to acclimate than are attached leaves with the conditions tested to data. Research has been initiated to develop techniques for evaluation of ability of plants to tolerate compacted soil conditions. Efforts to induce chromosome doubling were made with Forsythia and Philadelphus. Some treated plants have thicker, glossier leaves. These plants will be evaluated to determine ploidy level and stability.
Impacts
(N/A)
Publications
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Progress 01/01/87 to 12/30/87
Outputs
Evaluation of woody plant species and cultivars for adaptability to local climatic conditions continues as a major emphasis. Over 1200 new accessions were added in 1987. Breeding of Lonicera resistant to the witches broom aphid is continuing. Selected resistant F1 plants were crossed to combine better flower color and plant form with resistance. Breeding work with Viburnum was also continued. One selection with superior foliage and plant form will be recommended for introduction. Crossing of deciduous azaleas continues as a major effort. Other breeding efforts include Red Maple, Forsythia, and intergeneric crosses with Sorbus. In a study using a dialle crossing scheme within a full sib population of Rhododendron prinophyllum to determine system of self-incompatibility, results to date do not fit either of the classic models. Mutation breeding efforts were initiated using Sodium Azide and gamma irradiation on rooted cuttings of Cornus, Forsythia, Viburnum, and
Philadelphus. Propagation efforts for tissue culture propagation of Aesculus is continuing. Research to develop a technique for screening for tolerance to soil compaction is being initiated.
Impacts
(N/A)
Publications
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Progress 01/01/86 to 12/30/86
Outputs
Over 1000 new accessions of plants were acquired as evaluation of trees and shrubs for landscape qualities and adaptability to Minnesota's climate continues to be a major activity. An effort to evaluate broadlef evergreens in a microclimate shaded from the winter sun was initiated with the construction of wooden fences oriented in an east-west direction. Evaluation of new shade and ornamental tree species and cultivars continues as a high priority. Efforts are continuing to develop more cooperative efforts with other instiutions. Our record system has now been shifted completely to use of microcomputers for recording & maintenance of inventory and plant performance data. A concerted effort is being made to gather much needed data on plant performance especially in regard to adaptation to our winter cold, and insect and disease resistance.
Impacts
(N/A)
Publications
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Progress 01/01/85 to 12/30/85
Outputs
5 new plants were approved and named for introduction. These are 'Orchid Lights' and 'Golden Lights' Azaleas, a double-flowered selection of Prunus nigra named 'Princess Kay', 'Freedom' Honeysuckle selected for its resistance to the witches broom aphid, and Cornus sericea 'Cardinal' selected for its bright red winter stem color. Major breeding efforts are with Lonicera to combine aphid resistance with superior landscape qualities, Viburnum for improved foliage and plant habit, deciduous azaleas to complete selection of a series of hardy plants with a broad color range and to develop superior plant form and mildew resistance and intergeneric hybridization of Pomoideae. Results of initial efforts to develop tissue culture techniques for Aesculus 'Autumn Splendor' look promising. Cultures of excised embryos of Euonymus europaeus initiate many more adventitious shoots when submerged beneath media than when placed on the surface. Efforts have been initiated to evaluate
broadleaved evergreen rhododendrons for adaptation. 75 clones selected from those most likely to be winter hardy have been acquired and planted for evaluation. Breeding efforts are also underway to assess potential of breeding evergreen rhododendrons for adaptation to severe northern climates. Evaluation efforts with a wide range of landscape plants continues. Over 650 new accessions were added in 1985. Current evaluation emphasis is on shade trees, crabapples, Philadelphus, Weigela, Forsythia and Viburnum.
Impacts
(N/A)
Publications
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Progress 01/01/83 to 12/30/83
Outputs
Breeding to develop cold hardy deciduous azaleas is continuing. Pink Lights, Rosy Lights and White Lights were named and will be available on the retail market in 1984. Pollen of several azalea clones and selections were characterized to screen for occurrence of dyads (possibly unreduced gametes) to identify potential parents to use to overcome sterility barriers with tetraploid species and with hybrids from wide crosses with poor fertility. Thirteen selections of Viburnum were propagated for additional evaluation. A selection of Cornus sericea with bright red stem color will be recommended for release. Seedlings of Spiraea with dwarf habit and golden foliage in spring and fall look promising and will be evaluated further. Efforts to develop and identify Lonicera resistant to the honeysuckle aphid are continuing. Greenhouse screening of seedlings permits early rogueing of susceptible progeny. A visit sponsored by the Chinese Academy of Sciences to Northern China
resulted in collection of seed of a few species of woody plants for evaluation. Hopefully, development of additional cooperative efforts can result that will allow Chinese scientists to collect seed of many additonal species of woody plants for us to evaluate for adaptibility to our climate. Exploratory efforts to combine tissue culture techniques with irradiation breeding have been initiated.
Impacts
(N/A)
Publications
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Progress 01/01/82 to 12/30/82
Outputs
Work is continuing on development of cold hardly deciduous azaleas. Thirty seven new selections including many with yellow flowers were identified for propagation and further testing. One additional selection was chosen for introduction bringing the total to 4 selections now being propagated for introduction. Seed of Rhododendron prinophyllum was collected from the western end of its native range and R. calendulaceum was obtained from the northern end of its range. These sources will broaden the genetic base in our breeding program for adaptation to climate. Breeding efforts are continuing with Viburnum. Many seedlings appear to have outstanding foliage characteristics. Five selections were identified for propagation and further evaluation. Evaluations are being continued on selections of Cornus sericea, Fraxinus americana and Prunus nigra (a double flowered selection). Plants have been propagated for distribution to nurserymen cooperating in an evaluation
program. Efforts were increased to identify Lonicera resistant to the honeysuckle aphid. Breeding efforts were initiated. One resistant accession was chosen for propagation for wider evaluation and possible introduction. Breeding efforts were continued with Potentilla, Acer rubrum, and Sorbus (crosses with other closely related genera) and were initiated with Cotoneaster and Spiraea.
Impacts
(N/A)
Publications
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Progress 01/01/81 to 12/30/81
Outputs
A hardy Forsythia selection was registered as 'Northern Sun' and is being produced by nurseries for release in 1983. Names have been submitted for 3 clones of hardy azaleas now being propagated for introduction. A patent application was filed for 'Northwood' red maple and grower licenses have been issued to 7 production nurseries. Emphasis on breeding of cold hardy deciduous azaleas was continued. Equipment was obtained and a procedure developed that permits us to rapidly screen our progeny for flower bud hardiness. Thirty materials can be evaluated simultaneously by DTA analysis of floret freezing. Studies of pollen tetrads indicate that some 'Northern Lights' plants produce a low frequency of unreduced gametes. Utilizing those particular plants in crosses with tetraploid plants may overcome sterility problems. Additional cytogenetic studies are under way to aid in understanding sterility problems. Crossing efforts were continued with Viburnum and Acer rubrum.
Selections of Cornus sericea, Lonicera, and Fraxinus americana are being evaluated for possible introduction. Evaluations of a wide variety of shade tree clones and other woody plants for adaptability and landscape quality was continued with 1004 new accessions added. Efforts are under way to acquire Lonicera species that might be resistant to the Russian aphid. These will be evaluated and potential of breeding for resistance will be explored.
Impacts
(N/A)
Publications
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Progress 01/01/80 to 12/30/80
Outputs
Breeding emphasis with deciduous azaleas was continued. Three hundred and one different combinations of parents were crossed with 90 resulting in seed set. Results of laboratory hardiness evaluations indicate that R. viscosum and R. arborescens are hardy to -35 degrees C and may be useful as hardy parents. Selection and evaluation of Fraxinus americana and Acer rubrum was continued. Northwood red maple was named and will be introduced in 1981. A study of inheritance of photoperiod control of initiation of cold acclimation was completed. F1 progeny from crosses between northern and southern latitudinal ecotypes of cornus sericea began acclimation earlier than plants of southern parent but later than northern parents. Time of initiation of cold acclimation of F2 progeny from siblings was quite variable with a few individuals acclimating either later or earlier than either parental ecotype. Evaluation of a wide spectra of plant species for adaptability and
landscape qualities was continued. One thousand forty-four new accessions were planted. Laboratory screening for maximum midwinter hardiness capacity was continued and efforts were made to acquire types with sufficient hardiness to tolerate our midwinter temps. Initial evaluation of our replicated Betula planting was made for resistance to infestation by bronze birch borer. Contrary to reports Betula platyphylla japonica has severe infestation. Efforts are underway to verify accuracy of identification of the species in the study.
Impacts
(N/A)
Publications
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Progress 01/01/79 to 12/30/79
Outputs
Following hardening to their maximum potential, cold hardiness of approximately 100 species of deciduous woody plants was determined by laboratory procedures. Species showing sufficient hardiness are being acquired for testing under field conditions to determine if they can acclimate in sufficient time to withstand severe cold encountered in early winter. Additional clones of shade trees and accessions of other woody and herbaceous plants were acquired and planted for evaluation. One thousand four new accessions were added. A computerized system for maintaining inventory of plants under test and for collection and storage of performance data was developed and implemented. Breeding effort with deciduous azaleas was expanded. Germplasm of native species was collected from native sites at high elevations in North Carolina. Several new promising selections were made and propagated for further testing. Selection of superior plants of Cornus sericea was continued
from populations of previous crossing efforts. Weeping plant habit, dark stem color and purple fall color are dominant characteristics. More than 1 gene is involved in winter twig and fall leaf color. Preliminary results of hybridization of Gernanium species indicate that some interspecific crosses may be compatible. Both self-incompatible and self-compatible plants are found within the genus and often within the same species. Preliminary studies with Hypericum indicate that many species are self-compatible.
Impacts
(N/A)
Publications
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Progress 01/01/78 to 12/30/78
Outputs
New shade tree evaluation planting was initiated with emphasis on acquisition ofclones of Fraxinus and Acer rubrum. Additional clones have been ordered for planting Spring 1979. In total 830 new accessions of ornamentals were acquired for evaluation. Selection of superior trees of native Acer rubrum and Fraxinus americana continued. Breeding work continued with deciduous azaleas, redosier dogwood, viburnum and intergeneric hybridization of Pomoideae subfamily. Parental material was acquired to initiate exploratory breeding work with Hypericum, Clematis and Geranium species. In genetic studies F(1) progeny from crosses between northern and southern ecotypes of redosier dogwood are intermediate between parental types in leaf shape and time of cold acclimation. No maternal influence apparent. Intergeneric crosses between Sorbus x Aronia result in good pollen tube growth through style and good fruit set. Embryos, however, abort between 15 and 22 days.
Interspecific Cornus crosses within the bractless species indicate strong self incompatibility and little fruit set between most interspecies crosses. Styles were collected for studies of pollen tube growth. A cooperative plant testing program has been developed with Minnesota Nurserymen to give wider testing throughout state of promising new plant materials and to facilitate faster acceptance of new plants into the trade. Screening of plant materials for root cold hardiness is continuing.
Impacts
(N/A)
Publications
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Progress 01/01/77 to 12/30/77
Outputs
Breeding work between genera of Pomoideae was continued. Plants have been produced from crosses between Sorbus aucuparia x Cotoneaster multiflora and Sorbus aucuparia x Amelanchier grandiflora. Study of styles for pollen tube growth indicate that Sorbus aucuparia used as female is compatible with several other genera but mature fruit and seeds were not produced in the field on several of these combinations. Irradiation breeding work is being continued. A dwarf selection of Lonicera 'Zabel' is being evaluated for introduction. Anatomical studies of number of nodes developed in embryos of seeds or lateral buds can be helpful in determining which nodes to force following irradiation treatment. The process is time consuming and observing the number of nodes with leaves exhibiting primary effects following irradiation can give a good indication of number of nodes developed prior to irradiation. Breeding work with deciduous azaleas is being continued with efforts
aimed at selection for hardy plants with complete range of flower colors. Several selections being evaluated had fair to good bloom following the severe winter of 1976-77. Of special note was 1 with white flowers that had excellent bloom survival. To aid in improvement of techniques for laboratory screening of progeny for hardiness, a study was initiated to determine what effect age had on ability of seedlings to cold acclimate. Embryo culture techniques have been adapted to reduce stratification time in propagation of Viburnum crosses.
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Progress 01/01/76 to 12/30/76
Outputs
Reciprocal crosses were made between Cornus stolonifera clones that vary in timeof cold acclimation. Seedling populations will be grown for study of maternal influence on inheritance of cold acclimation. Selections that appear to be hardy were made of 45 azalea seedlings with a wide range of flower colors. 35 of these plants were propagated successfully by softwood cuttings for further evaluation. Evaluation of Cornus stolonifera selections for twig color, fall foliage color, plant form & disease resistance is continuing. Several additional selections were made from a seedling population derived by open pollination of an isolated planting of selected plants. Additional intergenericcrosses were made among Pyracantha, Amelanchier, Sorbus, Crataegus, Aronia, Pyrus, Malus and Cotoneaster. Best seed set was obtained on Sorbus with severalother genera used as male parents. These seeds will be grown to determine if they are of intergeneric origin. Crosses of Linicera
'Zabel' x Lonicera xylosteum nanum and Viburnum interspecific crosses were also successful in yielding seeds. Initial study of methods of handling materials following irradiation was completed with inconclusive results. Use of primary effects of leaves as indicators for selection of lateral buds does not appear feasible. Additional irradiation work has been initiated on seeds. Studies will be followed to determine which lateral buds on the seedlings should be forced.
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Progress 01/01/75 to 12/30/75
Outputs
Red deciduous leaves with morphology similar to the Malus male parent verify that three of several hundred seedlings grown from Pyracantha seed crosses are true intergeneric hybrids. Several hundred seedlings were also obtained from crossing Pyracantha with Amelanchier, Sorbus, Crataegus, Aronia and Cotoneaster,but their intergeneric validity has not yet been verified. Red Splendor flowering crabapple was compared to Dolgo and Columbia Crab for potential as a hardy seedling rootstock because of its fine growth characteristics, but was found to be incompatible with most scion cultivars tested. Several superior azalea, weigelia and ornamental blueberry seedlings were noted and numbered as advanced selections. Short internode compact Honeysuckle and Forsythia mutants were developed following gamma irradiation of dormant rooted cuttings.
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Progress 01/01/74 to 12/30/74
Outputs
Inability to root irradiated cuttings was overcome by irradiating rooted cuttings with lead shields to protect the roots. Appropriate dose was determined by correlating preliminary dose with shoot extension of forced buds rather than bud break which was giving inconsistent results. Over 200,000 seedswere obtained from F(1) hybrid azalea crosses for release to nurserymen illustrating feasibility of this procedure. Six azalea seedlings representing new color ranges were selected following cold winter temps which destroyed bloomon all non-hardy material. Seed set resulted from intergeneric crosses of Pyracantha with six other genera of Rosaceae. White pollen mutant Pinus resinosa crosses produced viable seedlings.
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Progress 01/01/73 to 12/30/73
Outputs
An F(1), seed propagated, hybrid cultivar of Rhododendron 'Mollis' x R. roseum will be released to the public. Several clones of superior individual quality will be released as clonally propagated cultivars when a reliable propagation production system is developed. A new pink hybrid azalea was selected with flower size equal to its orange flowered non-hardy parent. One outstanding and several promising flowering crabapple seedlings were selected. Dormant shoots of Forsythia, Viburnum, Cornus and Malus were irradiated to develop dwarf forms,but poor rooting viability was encountered and further tests are underway to refine the technique. Irradiated, mutant shoots of Lonicera 'Zabel' were selected for propagation and further testing. A white pollen mutant of Pinus resinosa was found and is being used in genetic studies.
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Progress 01/01/72 to 12/30/72
Outputs
Crossing, cultural and evaluation studies continued on Rhododendron and other genera. The hybrid azalea proposed for commercial introduction demonstrated ability to bloom satisfactorily following temperatures of -35-40F. To develop dwarf types of woody ornamentals, cuttings of Lonicera "Zabel" and seedlings of Sorbus aucuparia and Viburnum dentatum were irradiated. Plants propagated from lateral buds will be evaluated for effectiveness of treatment. Atmospheric treatment with ethylenimine is also being evaluated. Crossing and selfing experiments with a white pollen producing red pine, P. resinosa, produced seed and living offspring. Preliminary biochemical analysis of pollen has been carried out. A cross was made between Populus tremula "Erecta" and native P. tremuloides, with aim to select a seedling as alternative for Lombardy poplar.
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Progress 01/01/71 to 12/30/71
Outputs
Normal crossing, growing and evaluation procedures of the breeding program were continued. In a cultural study of seedling azaleas conducted at the Horticultural Research Center, young plants watered with distilled water grew distinctly better than those receiving tap water. Providing 24 hour supplemental lighting on the same materials did not improve growth. A pollen tube growth study was initiated in Rhod. kosterianum x Rhod. roseum progeny populations and in several other Rhod. seedling populations. A study of the possibility of breaking incompatibility in crabapple by 37 C. heat treatment, proven effective in Lilium and other genera, was intiated. The results were notentirely satisfactory because of air movement and insufficient humidity in the growth chambers which dried many of the stigmas and styles.
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Progress 01/01/70 to 12/30/70
Outputs
In addition to normal crossing, growing and evaluation procedures of the breeding program, primary emphasis was placed on investigations envolving refinement and utilization of freezing curves in studying cold tolerance in woody materials. The method was successfully applied to measurement of killing point of flower buds of Prunus avium, Sweet Cherry. Excised flower buds were cooled at 3, 15, 190 and 6,000C/hour. All estimates of killing temperature were similar and in agreement with the standard test method of cooling intact buds at 3C/hour. In contrast, increasing the cooling rate of intact flower buds above 3C/hr resulted in raising the killing point to the non-lethal freezing point of surrounding vegetative tissues. When thawing time was carefully controlled repeated tests of the same bud produced almost identical freezing point temperatures. When azalea buds were tested immediately after exposure to several days of naturally occuring sub 0F temperatures no
exotherm could be observed but death occurred before termination of the test at -50C. Florets killed in this way remained green and dry after thawing whereas florets containing sufficient moisture to generate an exotherm on freezing, turned blacksoon after thawing. Rhizoctonia was shown to be the cause of browning and deathof azalea cuttings being rooted in plastic covered propagation flats. Control was attained with sanitation and terraclor treatment. Grower production problems resulted in an almost total loss of the first year seedlings of the Rhod. roseum x mollis hybrid scheduled for introduction.
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Progress 01/01/69 to 12/30/69
Outputs
A decision was made to introduce to the public as a new variety the seed propagated F(1) progeny of the cross, Rhododendron (Mollis Hybrid) x Rhod. roseum. Official introduction will occur in approximately 3-4 years when an adequate supply of saleable plants is available. F(1) seed is now being distributed to interested growers. This cultivar has flower buds capable of surviving temperatures of -37C. The decision to introduce a seed propagated population resulted from repeated failures to root selected plants in commercially significant numbers. Progeny of backcrosses of the above F(1) to Mollis Hybrids and F(1) progeny of crosses of Exbury Hybrids x R. roseum failed in the first test winter conditions to achieve levels of hardiness equal to R. (Mollis Hybrid) x R. roseum progeny. Using the freezing curve method of determining killing temperatures of azalea buds, preliminary studies were inititated on intra plant variability in winter flower bud hardiness. Buds
located 6" to 8" below snowline exhibited mean killing temperatures from 2.1C to 10.5C above those observed for buds located 6" to 8" above snowline. Exposing these "split plants" to naturally occurring temperature levels between the hardiness readings the two parts of the plant resulted in 47% to 100% mortality of buds previously located below snowline. No injury was observed on hardier buds located above snowline. Electrophoretic studies, using azalea leafextracts, were initiated to determine feasibility of using this method to confirm or determine taxonomic relationships in Rhododendron. Using a peroxidase stain, certain banding patterns were common to known taxonomic groupsand absent in others.
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Progress 01/01/68 to 12/30/68
Outputs
Flowering crabapple 11AB was named 'Sparkler' and released for retail distribution in the spring of 1969. Progeny of the cross, Rhododendron mollis xR. roseum continued to be superior in hardiness and floral characteristics to azalea varieties currently available in the upper midwest. Selected clones of this cross will be introduced if proper propagation techniques can be developed.Efforts to root cuttings were largely unsuccessful until this year. Limited success on a small trial basis was achieved this year. Using a growth chamber with constant light, high humidity and relatively warm soil temperature produced90% rooting of one clone. There was considerable clone to clone variability in rooting. The technique of using freezing curves to determine temperatures lethal to Rhododendron florets was successfully used on the stem tissue of this genus as well as Malus, Forsythia and Acer. Temperatures found lethal to azaleaflorets using the freezing curve method were
closely correlated with temperatures at which natural injury occurs. In one instance a drop of the outside temperature just 1 C. below the temperature estimated to be lethal by the freezing curve resulted in the death of 60% of the florets studied. A studyof seasonal changes in hardiness showed that hardy clones responded to mid-winter cold periods with rapid increases in cold tolerance whereas non-hardymaterials did not.
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