Progress 11/07/99 to 07/31/04
Outputs
1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter? This project focuses on determining etiology and improved management strategies for key diseases of small fruits and deciduous tree crops. Objective 1 is to determine the causal agents of Prunus replant disease (PRD) etiology by correlating the incidence of the disease with quantitative and qualitative shifts in the microbial communities inhabiting the host's roots and surrounding soil and completing Koch's postulates with suspect microorganisms. The research approach is using culture-based isolations and culture-independent molecular characterizations of the microbial communities in replicated field plots where PRD incidence can be manipulated. Complementary greenhouse assays will determine effects of semi-selective chemical and physical soil treatments that permit independent evaluation of fungal
and bacterial roles in PRD. Culturable microbes shown to be associated with the incidence of PRD will be tested for pathogenicity on peach seedlings. Objective 2 is to develop improved diagnostic detection methods for pathogenic Phytophthora spp. that affect strawberry and deciduous fruit and nut crops. Described and novel PCR primers will be tested for specific amplification of mitochondrial DNA (mDNA) from P. cactorum, P. citricola, and P. megasperma extracted from soil and plant samples. Objective 3 is to improve management strategies for economically important soilborne diseases of fruit and nut crops. Chemical and cultural alternatives to methyl bromide will be tested for control of PRD, and genetic resistance to Phytophthora spp. will be explored in promising walnut rootstocks and new strawberry cultivars. (BROWNE) This project is being replaced by project #5306-22000-013-00D. 2. List the milestones (indicators of progress) from your Project Plan. Objective 1: Prunus replant
disease (PRD) etiology a) Establish and sample fumigated and non-fumigated plots on land at risk for PRD (2004-06). b) Culture and identify organisms associated with PRD (2004-08). c) Quantify nematodes associated with PRD (2004-06). d) Characterize DNA associated with PRD using denaturing gradient gel electrophoresis (DGGE) method (2004-06). e) Characterize DNA associated with PRD using oligonucleotide fingerprinting of ribosomal genes (OFRG) method (2005-07). f) Conduct soil treatment assays in the greenhouse (2004-05). g) Conduct fractionation assays in the greenhouse (2004-06). h) Conduct pathogenicity tests in greenhouse (2004-08) i) Analyze data, prepare and submit manuscripts (2005-08) Objecitve 2: Develop improved diagnostic detection methods for pathogenic species of Phytophthora that affect strawberry a) Optimize PCR for P. cactorum using genus-specific primers (2004) b) Optimize PCR for P. cactorum using species-specific primers (2004-05) c) Optimize sampling
for PCR detection of P. cactorum on strawberry plants (2004-05) d) Test and optimize PCR for P. cactorum in soil (2005-06) e) Validate PCR for P. cactorum with field strawberry and soil samples (2005-07). f) Develop and optimize primers for P. cinnamomi, P. citricola, and P. megasperma (2006-08) g) Analyze data, prepare and submit manuscripts (2005-08) Objective 3. Improve management strategies for economically important soilborne diseases of fruit and nut crops a) Test fumigant MB alternatives in almond and walnut nurseries and almond orchards (2004-2008) b) Evaluate cover crop and fallow treatments for PRD management, microplots (2004-06). c) Field test resistance to P. cactorum in strawberry cultivars (2004-08). d) Evaluate ressistance in Paradox walnut clones (2004-06) e) Evaluate Chinese wingnut /English walnut graft compatibility (2004-08) f) Field test resistance to P. cinnamomi in Chinese wingnut (2004-08) g) Analyze data, prepare and submit manuscripts (2005-08)
(BROWNE) 3. Milestones: 3A. List the milestones (from the list in Q#2) that were scheduled to be addressed in FY04. How many milestones did you fully or substantially meet in FY04 and indicate which ones were not fully or substantially met, briefly explain why not, and your plans to do so. Milestones scheduled for significant progress in 2004 included Objectives 1 a-d and f-h; Objective 2 a-c; and Objective 3 a-f. Milestones for Objectives 1 a, b, and c; and 3 a-f were substantially met in 2004 although they will involve repeat or continued experiments in future years as shown in the milestone list above. Significant research effort remains before the milestones for Objectives 1 d and f-h are attained. Technical difficulties with PCR and DGGE conditions for milestone 1 d are being resolved and are not anticipated to be insurmountable. Greenhouse assay experiments for milestones for Objective 1 f-h are underway. Progress has been made for the Objective 2- a and c milestones, but
additional research is required to develop the species-specific primers needed before work on Objective 2-b begins. It is anticipated that the species-specific primers will be available in 2005. (BROWNE) 3B. List the milestones (from the list in Q#2) that you expect to address over the next 3 years (FY05, 06&07). What do you expect to accomplish, year by year, over the next 3 years under each milestone? Objective 1: Prunus replant disease (PRD) etiology a) Establish and sample fumigated and non-fumigated plots on land at risk for PRD (2004-06). " PRD-affected and healthy trees in replicate plots will be established annually; the plots will demonstrate practical control measures for the disease and provide ideal locations for sampling needed for PRD etiology studies. b) Culture and identify organisms associated with PRD (2004-08). " This will be done for each of the experiments above (1a). We will accumulate a large collection of fungal and bacterial microbes suitable for
pathogenicity tests during the period. c) Quantify nematodes associated with PRD (2004-06). " This will be done for each of the experiments above (1a) and determine if nematode damage is confounded with PRD. It is anticipated that, as in previous years (2000-03) PRD will occur in absence of significant populations of plant parasitic nematodes. If confirmed, this will deepen the understanding among the agricultural community of PRD as a unique disease. d) Characterize DNA associated with PRD using denaturing gradient gel electrophoresis (DGGE) method (2004-06). e) Characterize DNA associated with PRD using oligonucleotide fingerprinting of ribosomal genes (OFRG) method (2005-07). " . PCR, coupled with DGGE and, eventually, OFRG, will be conducted in several experiments annually on samples preserved at -80DGC from Objective 1b. Bacterial and fungal rDNA primers will be used to produce culture- independent molecular "fingerprints" of the PRD and healthy microbial communities.
DNA "fingerprinting" is required to augment the culture- based approach (1-b) because most soil microbes are not culturable. The PCR/DGGE approach will provide a basis for the powerful, although more elaborate technique of OFRG fingerprinting and for DNA sequencing designed to pinpoint specific organisms associated with PRD incidence. It is anticipated that 6 months to 1 year will be required to perfect each of the fingerprinting techniques and apply them effectively. Application of the techniques will continue for 2 to 3 years. f) Conduct soil treatment assays in the greenhouse (2004-05). g) Conduct fractionation assays in the greenhouse (2004-06). h) Conduct pathogenicity tests in greenhouse (2004-08) " For f-g, two experiments will be conducted annually over the next 3 years. The research of f and g will complement that of 1 a-e. The research of 1 h will be a critical part of completing Koch's postulates. constitute a complimentary nother approach to determining PRD etiology
i) Analyze data, prepare and submit manuscripts (2005-08) " Technical reports will be prepared and presented annually each year for the Almond Board of California and the International Methyl Bromide Alternatives Conference. Peer-reviewed publications will be prepared on bacterial and fungal aspects of PRD when data sets from 1a-h are complete. One peer-reviewed publication is expected in 2006 and another in 2007. Objecitve 2: Develop improved diagnostic detection methods for pathogenic species of Phytophthora that affect strawberry a) Optimize PCR for P. cactorum using genus-specific primers (2004) b) Optimize PCR for P. cactorum using species-specific primers (2004-05) c) Optimize sampling for PCR detection of P. cactorum on strawberry plants (2004-05) " For a, b, and c samples of strawberry confirmed by culture isolations to be infected with the pathogen will be used to test mitochondrial gene region primers specific for species of Phytophthora during 2004 and part of 2005;
and similar methods will be used to test species-specific primers for P. cactorum in 2005. Both sets of primers will be tested with DNA extracted from necrotic portions of root and crown tissue as well as tissues adjacent to the necrotic parts. These experiments will determine the specificity and reliability of the mDNA primer sets. d) Test and optimize PCR for P. cactorum in soil (2005-06). " Repeated PCR experiments will permit adaptation of PCR protocols developed for P. cactorum in strawberry plants to detection of the pathogen in soil. e) Validate PCR for P. cactorum in field samples of strawberry plants and soil (2005-07). " The PCR protocols developed under controlled conditions in 2 b-d will be tested with field samples of strawberry plants and soil. f) Develop and optimize primers for P. cinnamomi, P. citricola, and P. megasperma (2006-08) " In year 3 of this project, methods used to develop mDNA-based PCR for P. cactorum in strawberry will be used to adapt PCR for
detection of additional species of Phytophthora in deciduous fruit and nut crops. Additional years will be required for optimization and validation with field samples. g) Analyze data, prepare and submit manuscripts (2005-08). " A manuscript on PCR detection of P. cactorum in strawberry plants and soil is anticipated by 2007. Objective 3. Improve management strategies for economically important soilborne diseases of fruit and nut crops a) Test fumigant MB alternatives in almond and walnut nurseries and almond orchards (2004-2008) " Three commercial nursery trials and three commercial orchard trials with fumigant MB alternatives were established in the last year; during the next three years, plant growth, pest, and pathogen responses will be evaluated in each of the trials. b) Evaluate cover crop and fallow treatments for PRD management, microplots (2004-06). " Micro plot experiments evaluating these treatments will be repeated in each of the next two years, and the results will
provide a basis for commercial demonstration/experimentation. c) Field test resistance to P. cactorum in strawberry cultivars (2004-08). " Public and proprietary new releases of strawberry cultivars will be tested each year near Watsonville during the next three years. d) Evaluate resistance in Paradox walnut clones (2004-06) " One to two greenhouse screens of approximately five experimental and two standard Paradox rootstock clones will be completed in each of the next two years, and the results of the screens will be used to select clonal rootstocks for advanced field testing. e) Evaluate Chinese wingnut /English walnut graft compatibility and field test resistance to P. cinnamomi in Chinese wingnut (2004-08) " During the next three years, annual evaluations of established rootstock trials (two at Davis, two near Stockton, CA) will be used to evaluate the graft compatibility and field resistance of Chinese wingnut; the results will establish the value of Chinese wingnut for
use at sites infested by the pathogen. f) Analyze data, prepare and submit manuscripts (2005-08). " Annual oral and written reports will be presented to the Walnut Marketing Board. Two peer reviewed publications summarizing the Paradox and wingnut rootstock research are anticipated in 2005. (BROWNE) 4. What were the most significant accomplishments this past year? 4A. Walnut growers suffer significant economic loss from tree mortality caused by Phytophthora species. Paradox clones with partial (quantitative) resistance to Phytophthora citricola diverse seed families of Chinese wingnut with very high resistance to P. citricola and P. cinnamomi were identified at Davis in collaboration with the Gale McGranahan, Professor, University of California and Joe Grant, Farm Advisor, University of California Cooperative extension. An additional year of data was gathered and analyzed, thereby solidifying the accomplishment above. Commercial nurserymen and commercial orchardists are using the
Chinese wingnut for sites infested with P. cinnamomi and experimenting with the Paradox rootstock clones. 4B. Other significant accomplishments? Reduced rates of chloropicrin and other methyl bromide alternatives were determined to reliably prevent PRD. 4C. Significant activities that support special target populations? All of the research conducted under the project for almonds, walnuts, and strawberries have been presented statewide to growers in oral and written formats. (BROWNE) 5. Describe the major accomplishments over the life of the project, including their predicted or actual impact. Grapevine viruses. Use of grape rootstocks (mostly hybrids of mixed species) as indicators greatly facilitated detection of 'new' GTAs capable of causing union-incompatibility in young grafted plants. One fully characterized virus namely GLRaV-2RG was found in a foundation grapevine cv. Redglobe, which had tested negative in biological- and laboratory-based assays. Even though GLRaV-2RG is
related to GLRaV-2 type strain, it does not cause leafroll symptoms in the standard grape indicators. In addition to GLRaV-2RG, preliminary results of the rootstocks trials have indicated as many as five more sources with up to four GTAs lethal on different grape rootstocks. Also, our results suggest that certain rootstocks should be considered as additions to the list of grape virus indicators used in virus certification programs.In FY05, will have published (ms slated for submission by fall 2004) paper describing the molecular properties of GLRaV-2RG. In FYs 05, 06 and 07, we will continue to isolate, identify and characterize other GTAs causing graft-incompatibility. Viruses isolated will be partially or fully characterized and primers designed for utility in RT-PCR assays. With ongoing and planned rootstock trials, i.e. Trial 2003 (collections were grafted last year and first reading in 2004; Trial 2004 more collections to be grafted this year; and Trial 2005, transplanted in
2004 for use in 2005, we will identify new grape virus indicators to compliment existing ones in use in the grape virus-certification program to assist in the detection of recalcitrant GTAs. (UYEMOTO) In addition to those described above, the specific cause and general bioloby of perennial Phytophthora canker disease was determined, and effective control measures were developed for the disease. Almond growers statewide use the control measures developed by this programs research. (BROWNE) 6. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? We have attended international grape virus conferences, published research data and freely disseminated primer sequences for GLRaV-2RG to colleagues in Italy, Australia, Canada, Chile and Argentina.(UYEMOTO)
Technologies transferred include highly effective control measures for perennial Phytophthora canker disease and PRD. Continued field evaluations are needed to evaluate the commercial value of the walnut rootstock technology to nurserymen and growers under diverse conditions. (BROWNE) 7. List your most important publications in the popular press and presentations to organizations and articles written about your work. "Biology and management of replant disease and perennial Phytophthora canker", oral and written reports and poster presentation of research at the Almond Industry Conference, 11 December 2004 "Evaluating paradox clones for resistance to phytopthora crown and root rots"; oral and written report at the Walnut Research Conference, 29 January 2004; "Biology and management of Phytophthora diseases on strawberry"; oral and written reports to strawberry growers at meetings organized by UC Cooperative Extension; 16 March and 24 June 2004. Browne, G., Connell, J. Becherer, H.,
McLaughlin, S., Schneider, S. Lee, R., and Hosoda, E. 2003. Evaluation of rootstocks and fumigants for control of almond replant disease. Paper no. 11, Proceedings of 2003 Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions, San Diego, CA. Browne, G, Trout, T., Becherer, S., McLaughlin, S., Lee, R., Gartung, J., Gillis, M., Schneider, S., Bulluck, R. 2003. Pre-plant cropping and fallowing effects on severity of Prunus replant disease. Paper no. 44a, Proceedings of 2003 Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions, San Diego, CA. Browne, G., Becherer, H., McLaughlin, S., Fennimore, S., Duniway, J., Martin, F., Ajwa, H., Winterbottom, C., Guererro, L. 2003. Integrated management of Phytophthora on strawberry without methyl bromide. Paper no. 128, Proceedings of 2003 Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions, San Diego, CA.
Impacts
(N/A)
Publications
- Browne, G.T., DeTar, W.R., Sanden, B.L., Phene, C.J. Comparison of drip and sprinkler irrigation systems for applying metam sodium and managing stem rot of potato. Plant Disease. 2002. v. 86. p. 1211-1218.
- Uyemoto, J.K., Bulluck, III, L.R., Pethybridge, S., McCorkell, B., Asai, W. K. Horizontal spread of Ilarviruses in young trees of several peach cultivars. Plant Disease. 2003. v.87. p.75-77.
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Progress 10/01/02 to 09/30/03
Outputs
1. What major problem or issue is being resolved and how are you resolving it? New and emerging bacterial, phytoplasma, fungal, and viral diseases of deciduous tree fruits and nuts, and grapevine and strawberry cause significant production losses in these crops. Among these diseases are angular leafspot disease of strawberry, grapevine graft-incompatibility, a severe virus disease of strawberry, grapevine graft-incompatibility, a severe virus disease of plum, and Phytophthora lethal canker and root/crown rots. To address this problem disease etiology and epidemiology must be determined, improved pathogen detection and identification methods must be developed, and germplasm must be evaluated for resistance to infection and disease development. Effective and economic disease management strategies without reliance on the use of chemical pesticides are needed. Biological and cultural practice alternatives to soil fumigation with methyl bromide are being evaluated and
implemented for control of Phytophthora-induced diseases and replant disease on strawberry and deciduous fruit and nut crops in California. Genetic, cultural, and chemical components of integrated control strategies for these soilborne diseases are being tested. Unknown causes for replant disease are being determined. 2. How serious is the problem? Why does it matter? Several biotic and abiotic diseases cause significant production losses for deciduous tree fruit and nut, grapevine and strawberry growers. However, the etiologies of many diseases are unknown or poorly understood. This precludes development of improved biologically-based disease management strategies that do not rely on the use of chemical pesticides. Chemical pesticides, including methyl bromide, threaten worker and consumer safety, as well as environmental quality. Some of these diseases (e.g.) angular leafspot disease of strawberry) are of quarantine significance, and affect the export of plant material from
California. Development of methyl bromide alternatives is an urgent and serious international problem. The fumigant is scheduled for complete phase out in 2005, and methyl bromide alternatives carry risk (i.e., due to regulatory factors) or need further development. At plant nurseries, methyl bromide provides critical pre-plant soil sanitation needed to produce healthy pathogen- and nematode-free stock. In strawberry fields and deciduous orchards, the fumigant is used to control documented soilborne diseases and pests (i.e., Verticillium wilt, Phytophthora root and rots, plant parasitic nematodes) as well as poorly understood diseases (i.e., replant disease) that compromise productivity of fruit and nut crops. Due to their different speciation, several grapevine rootstocks with resistance to phylloxera B strain are hypersensitive to graft-transmissible agents. 3. How does it relate to the National Program(s) and National Program Component(s) to which it has been assigned? The
research is related to NP 303, Plant Diseases (70%) and NP 308, Methyl Bromide Alternatives (30%). The overall purpose of the research is to provide new information regarding the etiology and epidemiology of biotic diseases of deciduous tree fruits and nuts, grapevine and strawberry in order to develop improved, economic, safe, environmentally sound disease management strategies based on reliable pathogen detection and identification, and genetic and cultural practices. 4. What were the most significant accomplishments this past year? 4A. What was your most significant accomplishment this past year? Almond growers that face orchard replant failures due to replant disease need pre-plant strategies for avoiding the disease without using methyl bromide. In collaboration with J. H. Connell of the University of California Cooperative Extension, we (Browne lab, CPGRU) conducted field experiments in Butte County, CA to determine optimized almond orchard replanting strategies. For improved
management of Almond Replant Disease, it was determined that a reduced rate of chloropicrin is as effective as methyl bromide or higher rates of chloropicrin; that Lovell peach rootstock is less susceptible than Marianna 2624 rootstock; and that scion type and planting method have little effect on disease severity. These findings are serving as a basis for amended treatment registrations for chloropicrin, almond rootstock selection by growers, and integrated prevention strategies for almond replant disease. 4B. Other significant accomplishments? Phytophthora crown and root rots are among the most important soilborne diseases affecting California walnuts, and conventional walnut rootstocks are highly susceptible to Phytophthora cinnamomi. Field trials were completed in Yolo and San Joaquin Counties, CA in collaboration with J. Grant, University of California Cooperative Extension, to test the potential of Chinese wingnut as a Phytophthora-resistant walnut rootstock. It was determined
that Chinese wingnut is highly resistant to Phytophthora crown and root rots and is graft compatible with some but not all walnut cultivars. Chinese wingnut rootstock could help growers improve productivity of walnut orchards at sites infested with Phytophthora cinnamomi. Grapevine rootstock stem lesion associated virus (GRSLaV) is lethal in young vineyards. Primer sequences of GRSLaV for PCR-based detection assays were developed and shared with colleagues in New Zealand and Argentina. GRSLaV was determined to impact rootstock 1616C as well as 3309C, Kober 5BB, Teleki 5C, and 1103P and presence of GRSLaV was confirmed by colleagues in New Zealand and Argentina. This assay will enable detection of the virus in scions and the 5 out of 18 commercially- used rootstocks that are highly sensitive to the disease may be avoided by growers. Almond union mild etch (AUME) is a genetic disorder expressed on the plum rootstock, Marianna 2624. Progenies were evaluated to identify a scion budwood
source with low potential for this condition. One Butte almond source (out of about 20 examined) which scored zero for AUME was identified. This single source may be used for future propagations of Butte almond by the California nursery industry. 4C. Significant activities that support special target populations? None 5. Describe the major accomplishments over the life of the project, including their predicted or actual impact. Determined that phosphonate products (fertilizers and fungicide formulations that release phosphorous acid) provide systemic protection from perennial Phytophthora canker diseases of almond; this is a short term solution to a long-standing cause of almond tree death in the San Joaquin Valley. Determined efficacy of alternative fumigants and cultural and genetic approaches for managing Phytophthora diseases on strawberry without methyl bromide; this has aided assessments of alternatives to methyl bromide for the strawberry industry and served as a basis for
integrated control strategies for Phytophthora crown rot of strawberry. Development of primer sequences of GRSLaV has permitted its detection using molecular methods in two foreign countries, indicating virus presences there. Source materials can be pre-screened by RT-PCR assays to determine sources free of this virus. 6. What do you expect to accomplish, year by year, over the next 3 years? In FY04, Will conduct research to determine unknown causes of replant disease on stone fruits and nuts and research on cultural and chemical alternatives to methyl bromide for control of the disease. New disease collections will be indexed across a panel of different grape rootstocks. This will serve to identify new sources of graft-transmissible agents capable of inducing acute interactions on specific rootstocks of varying Vitis speciation. FY05, attempt to identify the causal agent(s), develop diagnostic reagents for their detection, and conduce vineyard surveys to determine incidence and
distribution. Will continue research supporting development of integrated management strategies for control of Phytophthora root and crown rots of tree fruits and nuts and strawberries. FY06, continue vineyard surveys and identify new diseased vineyards for future indexings across the rootstock test panel. 7. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? Oral presentations on grapevine viruses scheduled for the ICVG meetings in Italy, September 2003. Also invited seminar on AUME was received from the University of Bari, Italy (presented ahead of the ICVG conference). Chemical, cultural, and genetic approaches to managing replant disease of almond and Phytophthora-induced diseases on strawberry, stone fruits and nuts, and walnut were transferred to
growers, pest control advisors, other industry representatives, and the scientific community in the form of oral and written reports. Most of the technologies are available to the public, but some chemical alternatives to methyl bromide face uncertain regulatory constraints. 8. List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: This does not replace your peer-reviewed publications listed below). Browne, G.T., Becherer, H.E., Vazquez, M.R., McLaughlin, S.A., Wakeman, R. J., Winterbottom, C.Q., Duniway, J.M., Fennimore, S.A. Outlook for managing Phytophthora diseases on California strawberries without methyl bromide. Proceedings of the Annual Research Conference on Methyl Bromide Alternatives. 2001. p. 29-1 to 29-2. Browne, G.T., Connell J.H., Bulluck, L.R., Trout, T.J., Schneider, S.M. Management and etiology of replant disorder on almond and peach. Proceedings of 2002 Annual International
Research Conference on Methyl Bromide Alternatives and Emissions Reductions. 2002. Paper no. 24. Uyemoto, J.K. Grapevine stem lesion viruses: A new grouping. Proceedings of the 54th Annual meeting of the American Society of Enology and Viticulture. Reno, NV. June 18-19, 2003.
Impacts
(N/A)
Publications
- Browne, G.T., DeTar, W.R., Sanden, B.L., Phene, C.J. Comparison of drip and sprinkler irrigation systems for applying metam sodium and managing stem rot of potato. Plant Disease. 2002. v. 86. p. 1211-1218.
- Uyemoto, J.K., Bulluck, III, L.R., Pethybridge, S., McCorkell, B., Asai, W. K. Horizontal spread of Ilarviruses in young trees of several peach cultivars. Plant Disease. 2003. v.87. p.75-77.
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Progress 10/01/01 to 09/30/02
Outputs
1. What major problem or issue is being resolved and how are you resolving it? Production losses due to new and emerging bacterial, phytoplasma, fungal, and viral diseases of deciduous tree fruits and nuts, and grapevine and strawberry. These include angular leafspot disease of strawberry, grapevine graft-incompatibility, a severe virus disease of plum, and Phytophthora lethal canker and root/crown rots. Determination of disease etiology and epidemiology, development of improved pathogen detection and identification methods, and evaluation of germplasm for resistance to infection and disease development. Development of effective, economic disease management strategies without reliance on the use of chemical pesticides, including development, evaluation and implementation of biological and cultural practice alternatives to soil fumigation with methyl bromide to manage soilborne diseases of these crops. 2. How serious is the problem? Why does it matter? Several
biotic and abiotic diseases cause significant production losses for deciduous tree fruit and nut, grapevine and strawberry growers. However, the etiologies of many diseases are unknown or poorly understood. This precludes development of improved biologically-based disease management strategies that do not rely on the use of chemical pesticides. Chemical pesticides, including methyl bromide, threaten worker and consumer safety, as well as environmental quality. Some of these diseases (e.g. angular leafspot disease of strawberry) are of quarantine significance, and affect the export of plant material from California. Use of methyl bromide for soil fumigation to control soilborne pathogens, such as Phytophthora root and crown rots, is being phased out. Due to their different speciation, several grapevine rootstocks with resistance to phylloxera B strain are hypersensitive to graft-transmissible agents. 3. How does it relate to the national Program(s) and National Program Component(s)
to which it has been assigned? The research is related to NP 303, Plant Diseases (70%) and NP 308, Methyl Bromide Alternatives (30%). The overall purpose of the research is to provide new information regarding the etiology and epidemiology of biotic diseases of deciduous tree fruits and nuts, grapevine and strawberry in order to develop improved, economic, safe, environmentally sound disease management strategies based on reliable pathogen detection and identification, and genetic and cultural practices. 4. What was your most significant accomplishment this past year? A. Most Significant Accomplishment During FY 2002 Year: Methyl bromide is scheduled for non-registered use in the US in the near future and alternative chemicals and/or controls must be developed. The USDA, ARS, Crops Pathology/Genetic Research Unit confirmed that pre-plant application of chloropicrin, a registered methyl bromide alternative, effectively controlled an almond replant disorder plaguing growers in
northern California. Research plots were established in commercial orchards in the Chico area. Based on preliminary results, chloropicrin may be an excellent replacement for methyl bromide on replant problem sites. B. 1) Newly planted vineyards for wine production have suffered from young vine decline and up to eight grapevine sources were identified as being infected with graft-incompatible agents (GIAs) capable of causing young vine decline. Work being done at the University of California, Department of Plant Pathology Field Facility on the Davis campus characterized one GIA in Redglobe table grape as a closterovirus and designated Grapevine rootstock stem lesion associated virus (GRSLaV). Primers were designed for RT-PCR assays and GRSLaV was further detected in 4 of 22 diseased samples of several wine grape cultivars, indicating this virus occurs in wine grape cultivars. Previously only fungi were known to be associated with young vine decline and now with the discovery and
characterization of one GIA, consideration now must include viruses and since publishing our findings, requests were received for GRSLaV-primer sequences from abroad (Australia, Chile, & Italy). 2) Viral diseases of prunus sp. constitue a serious threat to efficient fruit production. Published results of a three year study on Plum bark necrosis and stem pitting virus (PBNSPaV), characterized as another closterovirus unrelated to GRSLaV. Determined host responses among several Prunus species and developed RT-PCR assays for its detection. Primer sequences are now available for international distribution that will enhance virus detection and control. 5. Describe your major accomplishments over the life of the project, including their predicted or actual impact? Determined that systemic fertilizer/fungicide strongly suppresses development of lethal Phytophthora cankers on almond trees. This is a short-term solution for one major cause of tree loss for several Kern County growers.
Completed nursery graft compatibility trials for walnut scions propagated onto wingnut rootstock. Selections among the compatible walnut-wingnut combinations were used to establish field trials at UCD and in commercial orchards for continued evaluation of scion-stock compatibility, tree performance, and tolerance/resistance to Phytophthora cinnamomi. Also, clones of Paradox walnut seed families with resistance to Phytophthora citricola were provided to a commercial nursery for increase and rooting. The rate of spread of cherry leaf roll virus (CLRV) , the causal agent (CLRV-W) of walnut blackline disease to, and among, 2 walnut cultivars in California was determined. The effects of CLRV infection on growth and production (quantity and quality) of walnuts in California were also determined. In addition, study on the comparative effects of different rootstocks on growth and production on English walnut rootstock in California was completed. The relationship of CLRV-W in California
to other CLRV-W strains in Europe based on homology of genomic coat protein sequences was determined. An RT-PCR assay for CLRV-W detection in infected walnut trees was developed. A bioassay for improved detection and identification of Xf based on inoculation of detached strawberry leaves from greenhouse-grown plants was developed. Detached leaf bioassay and PCR protocols were evaluated and adapted to detect and identify Xf in symptomatic and asymptomatic clinical strawberry field samples. The comparative genomic fingerprinting of several California Xf strains by BOX-, ERIC- and REP- PCR was characterized. Xf-resistant and -susceptible germplasm among commercial strawberries grown in California were identified. Up to eight different graft-transmissible agents were detected in grapevines based on differential responses on various grape rootstocks. These findings will allow nurserymen to prescreen scion sources to determine the health of selected scions in the grapevine
certification program. 6. What do you expect to accomplish, year by year, over the next 3 years? In FY03, identify grapevine sources with different graft-incompatible agents (GTAs). Elucidate unknown causes for replant disorders affecting establishment of Prunus orchards. In FY04, molecularly characterize and develop primers for RT-PCR detection for new GTAs. Develop chemical and cultural management strategies to control Prunus replant disorders. In FY05, conduct vineyard surveys with newly developed primers to determine incidence and distribution of recently discovered GTAs. Characterize genetic diversity of Phytophthore cactorum and P. citricola populations isolated from almond and strawberry and develop control measures for these diseases. 7. What technologies have been transferred and to whom? When is the technology likely to become available to the end user (industry, farmer other scientist)? What are the constraints, if known, to the adoption durability of the technology?
Oral presentations and publications on the discovery and partial characterization of the GRSLaV and PBNSPaV were made. Primer sequences for use in RT-PCR assays for both have been published and the technology was made public. Chemical, cultural, and genetic disease management programs were transferred to almond, strawberry, and walnut stakeholders. The almond, strawberry, and wingnut rootstock technologies are available to growers. However, some of it is constrained by regulatory (pesticide registration) or economic factors. Also, until improvements are made in ease of propagations, it is currently uneconomical to pursue the commercial use of paradox as a rootstock. 8. List your most important publications and presentations, and articles written about your work (NOTE: this does not replace your review publications which are listed below) Browne, G.T., Bulluck, L.R., Connell, J.C., Trout, T.J. Determining unknown causes for replant disorder of Prunus species in California.
Proceedings of Annual Research Conference on Methyl Bromide Alternatives. 2001. p. 102-1 to 102-4. Browne, G.T., DeTar, W.R., Sanden, B.M., Phene, C.J. Comparison of drip and sprinkler irrigation systems for applying methan sodium and managing stem rot on potato. Plant Disease (accepted). Browne, G.T., Viveros, M.A. Lethal cankers caused by Phytophthora spp. in almond scions: Specific etiology and potential inoculum sources. Plant Disease. 1999. v.83. p. 739-745. Uyemoto, J.K., Rowhani, A., Luvisi, D., Krag, C.R. Discovery of a new Closterovirus in Redglobe grape causing decline of grafted plants. California Agriculture. 2001. v. 55(4). p. 28-31. Marini, D.B., Zhang, Y.P., Rowhani, A., Uyemoto, J.K. Etiology and host range of a Closterovirus associated with plum bark necrosis-stem pitting disease. Plant Disease. 2002. v. 86. p. 415-417. Marini, D.B., Rowhani, A., Uyemoto, J.K. Discovery of a new graft- transmissible agent causing bark necrosis and stem pitting in 'Black Beaut' plum
and symptoms in other Prunus species and varieties. California Agriculture 2002. v. 56(3). p. 108-111. Browne, G.T., Becherer, H.E., Vazquez, M.R., Wakeman, R.J. Phytophthora control on strawberry, almond, and walnut without methyl bromide. Proceedings of Annual Research Conference on Methyl Bromide Alternatives. 1999. p. 82-1 to 82-3. Browne, G.T., Becherer, H.E., Vasquez, M.R., McLaughlin, S.A., Wakeman, R.J., Winterbottom, C.Q., Duniway, J.M., Fennimore, S.A. Outlook for managing Phytophthora diseases on California strawberries without methyl bromide. Proceedings of Annual Research Conference on Methyl Bromide Alternatives. 2001. p.29-1. Browne, G.T., Bulluck III, L.R., Connell, J.C., Trout, T.J. Determining unknown causes for replant disorder of Prunus species in California. Proceedings of Annual Research Conference on Methyl Bromide Alternatives. 2001. p. 102-1 to 102-4. Duniway, J.M., Hao, J.J., Dopkins, D.M., Ajwa, H., Browne, G.T. Chemical, cultural, and biological
alternatives to methyl bromide. Proceedings of Annual Research Conference on Methyl Bromide Alternatives. 2001. p. 41-1 to 41-2. Fennimore, S., Martin, F., Duniway, J., Browne, G., Ajwa, H., Winterbottom, C., Westerdahl, B., Goodhue, R., Haar, M., Bull, C. Alternative fumigants for control of soil pests: Strawberry as a model system. Proceedings of Annual Research Conference on Methyl Bromide Alternatives. 2001. p. 96-1. Browne, G.T., Viveros, M.A., Lethal cankers caused by Phytophthora spp. in almond scions: Specific etiology and potential inoculum sources. Plant Disease. 1999. v. 83. p. 739-745.
Impacts
(N/A)
Publications
- Marini, D.B., Zhang, Y.P., Rowhani, A., Uyemoto, J.K. Etiology and host range of a Closterovirus associated with plum bark necrosis-stem pitting disease. Plant Disease. 2002. v. 86. p. 415-417.
- Marini, D.B., Rowhani, A., Uyemoto, J.K. Discovery of a new graft- transmissible agent causing bark necrosis and stem pitting in 'Black Beaut' plum and symptoms in other Prunus species and varieties. California Agriculture. 2002. v. 56(3). p.108-111.
- Uyemoto, J.K. Almond diseases caused by phytoplasmas. Teviotdale, B.L., Michailides, T., Pscheidt, J. editors. The American Phytopathology Society. Compendium of Temperate Nut Crop Diseases. 2002. p. 34-35.
- Uyemoto, J.K. Almond diseases caused by viruses. Teviotdale, B.L., Michailides, T., Pscheidt, J. editors. The American Phytopathology Society. Compendium of Temperate Nut Crop Diseases. 2002. p. 36-38.
- Uyemoto, J. K. Noninfectious disorders of almond. Teviotdale, B.L., Michailides, T., Pscheidt, J. editors. The American Phytopathology Society. Compendium of Temperate Nut Crop Diseases. 2002. p. 39.
- Uyemoto, J.K. Nutritional Disorders in Almond. Teviotdale, B.L., Michailides, T., Pscheidt, J. editors. The American Phytopahtology Society. Compedium of Temparate Nut Crop Diseases. 2002. p. 41-42.
- Westphal, A., Browne, G.T., Schneider, S. Evidence for Biological Nature of the Grape Replant Problem. California. Plant and Soil Journal. 2002. v. 242. p.197-203.
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Progress 10/01/00 to 09/30/01
Outputs
1. What major problem or issue is being resolved and how are you resolving it?
Production losses due to new and emerging bacterial, phytoplasma, fungal and viral diseases of deciduous tree fruits and nuts, grape and strawberry. These include angular leafspot disease of strawberry, grapevine graft-incompatibility, X-disease of cherry, and Phytophthora root and crown rots. Determination of disease etiology and epidemiology, development of improved pathogen detection and identification methods, and evaluation of germplasm for resistance to infection and disease developoment. Development of effective, economic disease management strategies without reliance on the use of chemical pesticides, including development, evaluation and implementation of biological and cultural practices alternatives to soil fumigation with methyl bromide to manage soilborne diseases of these crops.
2. How serious is the problem? Why does it matter?
Several biotic and abiotic diseases cause significant production losses for deciduous tree fruit and nut, grape and strawberry growers. However, the etiologies of many of these are unknown or poorly understood. This precludes development of improved biologically-based disease management strategies that do not rely on the use of chemical pesticides. Chemical pesticides, including methyl bromide, threaten worker and consumer safety, as well as environmental quality. Some of these diseases (e.g. angular leafspot disease of strawberry) are of quarantine significance, and affect the export of plant material from California. Use of methyl bromide for soil fumigation to control soilborne pathogens, such as Phytophthora root and crown rots, is being phased out. Due to their different speciation, several of the phylloxera B-resistant rootstocks widely used in California grape plantings are hypesensitive to unknown graft-transmissible agents.
3. How does it relate to the National Program(s) and National Component(s)?
The research is related to NP 303, Plant Diseases (70%) and NP 308, Methyl Bromide Alternatives (30%). The overall purpose of the research is to provide new information regarding the etiology and epidemiology of biotic diseases of deciduous tree fruits and nuts, grape and strawberry in order to develop improved, economic, safe, environmentally sound disease management strategies based on reliable pathogen detection and identification, and genetic and cultural practices.
4. What were the most significant accomplishments this past year?
A. Single Most Significant Accomplishment During FY 2001 Year: Determination of strawberry germplasm susceptibility to Phytophthora species, and crown and root rot diseases. There is a need to develop non-chemical alternatives to pre-plant soil fumigation with methyl bromide to effectively manage soilborne diseases of horticultural crops, such as strawberry, in California. Strawberry germplasm was evaluated for susceptibility/resistance to infection by Phytophthora species, and development of strawberry crown and root rot diseases. UC strawberry germplasm ranges from highly resistant to highly susceptible to Phytophthora cactorum, while all cultivars tested were susceptible to Phytophthora fragariae var fragariae. This information will contribute to development of disease resistant commercial strawberry varieties based on genetic host resistance for part of integrated disease management strategies as alternatives to pre-plant soil fumigation with methyl bromide. B. Other
Significant Accomplishments: 1. Evaluation of systemic fungicide and methyl bromide alternative fumigants. There is a need to develop chemical alternatives to pre-plant soil fumigation with methyl bromide to effectively manage soilborne diseases of horticultural crops, such as almond and strawberry, in California. Systemic fungicides (fosetyl-Al, mefenoxam) and methyl bromide fumigant alternatives (chloropicrin, propargyl bromide, methyl iodide) were evaluated for effectiveness in controlling almond replant disorder and Phytophthora crown rot of strawberry. Tree-site injections with chloropicrin controlled most of the almond replant disorder; and fosetyl-Al and mefenoxam partially controlled Phytophthora crown rot of strawberry. This information will contribute to development of integrated disease management strategies as alternatives to pre-plant soil fumigation with methyl bromide. 2. Developed effective control of lethal Phytophthora canker disease of almond. Lethal
Phytophthora canker disease has killed more than 5% trees in several affected orchards in California. Phosphonates were evaluated for management of lethal Phytophthora canker disease of almond. Determined that phosphonates provide effective preventative and curative control of lethal Phytophthora canker of almond. This information will guide orchard management to reduce incidence of lethal Phytophthora canker (a scion disease), and may improve control of Phytophthora root and crown rots. 3. Discovery of graft-transmissible agents associated with graft-incompatibility in grafted grapevine. Throughout California, newly planted vineyards have displayed poor plant growth and development; however, the cause(s) are unknown. Grapevine virus cultures and collections from commercial vineyards were graft-inoculated across a panel of 18 different grape rootstocks. Potentially, 5 new graft- transmissible agents causing graft-incompatibility in grafted grape plants were detected, with one of
these (Redglobe collection) identified as a clostervirus and designated as grapevine rootstock stem lesion disease-associated virus (GRSLaV). This information will be used to develop diagnostic tests for use in the California Grapevine Registration and Certification Program. 4. Demonstrated effective management of bacterial angular leafspot disease of strawberry by induced systemic (acquired) resistance. Bacterial angular leafspot disease of strawberry, caused by Xanthomonas fragariae, is a chronic disease that can cause serious economic losses in fruit production fields in California, as well as reduced value of strawberry nursery planting stock exported from California. Two commercially available chemicals (a derivative of salicylic acid; a harpin-based product) were evaluated to induce systemic acquired resistance to infection of strawberry by Xanthomonas fragariae and development of bacterial angular leafspot disease in strawberry. Both materials effectively controlled
bacterial angular leafspot disease of strawberry in a commercial fruit production field for the third year in a row. This information will contribute to effective management of bacterial angular leafspot disease of strawberry in California nurseries and fruit production fields, enhancing the quality of strawberry planting stock for export and domestic use. 5. Initiated assessment of molecular-based (PCR) methodology to detect and identify Xylella fastidiosa in sub-clinically infected grapevines and in the glassy-winged sharpshooter. Although relatively reliable serological and molecular-based techniques are available for detection and identification of Xylella fastidiosa (Xf) in infected/diseased plant material, the reliability of these techniques to detect and identify Xf in sub-clinically infected plant material is not known. The reliability of detecting and identifying Xylella fastidiosa (Xf) using available PCR primers and amplicon detection by agarose gel electrophoresis was
assessed by amending grape leaf petiole extracts with different amounts of Xf. The frequencies of Xyella fastidiosa (Xf) detection in amended grape leaf petiole extracts were 100%, 0 - 98%, and 0% for Xf concentrations >105, 102 -105, and <102 cells/ml, respectively. This information will be used for early detection of Xylella fastidiousa in sub-clinically infected grapevines, as well as other plants, and for determining the incidence of Piece's disease. C. Significant Accomplishment/Activities That Support Special Target Populations: None
5. Describe the major accomplishments over the life of the project including their predicted or actual impact.
Determined that systemic fertilizer/fungicide strongly suppresses development of lethal Phytophthor cankers on almond trees. This is a potential short-term solution for a major source of tree loss for several Kern County growrs. Completed nursery graft compatibility trials for walnuts graafted onto wingnut rootstock. Selected compatible walnut-wingnut combinations were used to establish field blocks at UCD and in commercial orchards for further evaluation for compatibility, tree growth, and resistance to Phytophthora cinnamomi. Clones of Paradox walnut seed families with reistance to Phytophthora citricola were provided to a commercial nursery for further increase and rooting. The rate of spread of cherry leafroll virus (CLRV), the causal agent (CLRV-W) of walnut blackline disease to, and among, 2 walnut cultivars in California was determined. The effects of CLRV infection on growth and production (yield and quality) of walnuts in California were determined. The comparative
effects of different rootstocks on growth and production of English walnuts in California were determined. The relationship of CLRV-W in California to other CLRV-W strains in Europe based on homology of genomic coat protein sequences was determined. A PCR assay for CLRV-W detection in naturally infected walnut trees was developed. A bioassay for improved detection and identification of Xf based on inoculation of detached strawberry leaves from greenhouse-grown plants was developed. Detached leaf bioassay and PCR protocols were evaluated and adapted to detect and identify Xf in symptomatic and asymptomatic clinical strawberry field samples. The comparative genomic fingerprinting of several California Xf strains by BOX-, ERIC- and REP-PCR was characterized. Xf-resistant and -susceptible germplasm among commercial strawberries grown in California were identified. Two different graft-transmissible agents have been detected in grapevines based on differential responses of various
grape rootstocks. These findings will allow nurserymen to prescreen scion sources to determine the health of selected rootstocks in the grapevine certification program.
6. What do you expect to accomplish, year by year, over the next 3 years?
Year 1: Identification of effective methyl bromide alternatives for management of the almond replant problem in Northern California. Continue determination of the role(s) of newly discovered/identified graft-transmissible agents (GTAs) in poor plant growth and development in newly planted vineyards in California. Propagate own-rooted source plants of new grapevine GTAs. Continue assessment and characterization of chemically and biologically induced systemic acquired resistance to control bacterial angular leafspot disease of strawberry and Pierce's disease of grapevines. Continue development of improved methodology to reliably detect low levels of Xylella fastidiosa in sub-clinically plant tissue that does not rely on amplicon detection by agarose gel electrophoresis. Continue evaluation of chemicals for systemic acquired resistance on development of Pierce's disease symptoms in commercial vineyards in California. Initiate experiments to evaluate the effect(s) of grape
rootstocks (White Riesling, Chenin Blanc) on infection of susceptible grape cultivars (Cabernet Sauvignon, Chardonnay, Merlot) on infection by Xylella fastidiosa and development of Pierce's disease. Year 2: Determine unknown biological causes of the Prunus (almond, peach) replant problem in California. Identify effective methyl bromide alternatives for management of Phytophthora in California strawberry production systems. Purify dsRNAs from own-rooted sources of new grapevine graft- transmissible agents (GTAs), amplify with random primers in RT- PCR, clone and characterize PCR-derived products, and design specific primers for these GTAs. Complete evaluation of chemicals for systemic acquired resistance to development of Pierce's disease in commercial vineyards in Southern California. Continue evaluation of chemicals for systemic acquired resistance to development of Pierce's disease in commercial vineyards in the lower San Joaquin Valley of California. Continue haracterization
of systemic acquired resistance in strawberry and grapevines to bacterial angular leafspot disease and Pierce's disease, respectively. Continue evaluation of rootstocks on infection of grapevines by Xylella fastidiosa and development of Pierce's disease. Year 3: Identify and develop cultural practices strategies that contribute to successful management of the Prunus replant problem in California. Test designed primers for new grapevine graft- transmissible agents (GTAs) and correlate with original GTA sources. Complete characterization of systemic resistance in strawberry and grapevines to bacterial angular leafspot disease and Pierce's disease, respectively. Complete evaluation of rootstocks on infection of grapevines by Xylella fastidiosa and development of Pierce's disease. Complete evaluation of chemicals for systemic acquired resistance to development of Pierce's disease in commercial vineyards in the lower San Joaquin Valley of California.
7. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end user (industry, farmer, other scientists)? What are the constraints if known, to the adoption & durability of the technology product?
Almond growers have implemented control measures for lethal Phytophthora canker disease based on results in Kern County, California, field experiments. (Browne) One California strawberry nursery and one California strawberry grower have incorporated chemically induced systemic acquired resistance for management of bacterial angular leafspot disease. Constraints include uncertainty about long-term effects on fruit production performance of strawberry nursery stock treated in the nursery, and cost for large scale use. (Civerolo) A proposal for revision of rice quarantine regulations was submitted to APHIS. (Mackill) Primer sequences of RT-PCR assays for detection of grapevine closteroviruses were provided to Agri-Analysis, Inc., a commercial diagnostic laboratory. Constraints include need for knowledge of, and experience with, molecular diagnostic techniques, and cost. (Uyemoto)
8. List your most important publications in the popular press (no abstracts) and presentations to non-scientific organizations and articles written about your work (NOTE: this does not replace your peer-reviewed publications which are listed below)
Control measures for management of lethal Phytophthora canker disease. Annual Almond Industry Conference, 2000, Modesto, CA. (Browne) Effects of cover crops on replant and nursery tree growth. California Association of Nurserymen. September 28, 2000. Davis, CA. (Browne) Biology and management of soilborne diseases of fruit and nut trees. Tree and Vine Management School, Plant Disease Management Workshop. October, 2000. Tulare, CA. (Browne) Determining unknown causes of Prunus replant problems. October 24, 2000. (Browne) Etiology and control of replant disorder. Annual ARS-sponsored methyl bromide alternative meeting, 2001. Fresno, CA. (Browne) Genetic screens of strawberries for resistance to Phytophthora fragariae var. fragariae and Phytophthora cactorum. Annual Strawberry Research Field Days, 2001. Irvine, Oxnard, Santa Maria and Watsonville, CA. (Browne) Methyl bromide alternatives for management of Phytophthora cactorum in commercial strawberries and nurseries, Annual
Strawberry Research Field Days, 2001. Irvine, Oxnard, Santa Maria and Watsonville, CA. (Browne) Prunus replant problem. February 7, 2001. Watsonville, CA. (Browne) Management of bacterial angular leafspot disease of strawberry by systemic acquired resistance. California Strawberry Nurserymen. May 30, 2001. Red Bluff, CA. (Civerolo) Grapevine scion-rootstock incompatibility. 6th Romeo Bragato Conference sponsored by the New Zealand Grape Growers Council. Nelson, New Zealand. August 24-26, 2000. A new culprit detected in young vine decline. In: Trellis Talk Newsletter. Pages 2 & 4, March 2001. (Uyemoto) Nuredin, N. and Symons, R.H. A destructive virus from Red Globe table grape. The Australian Grapegrower & Winemaker. Pages 16, 18, 20. April 2001. (Uyemoto)
Impacts
(N/A)
Publications
- Uyemoto, J.K., Rowhani, A., Luvisi, D., Krag, C.R. Discovery of a new closterovirus in Redglobe grape causing decline of grafted plants. California Agriculture. July-August 2001. v. 55 p. 28-31.
- Bruening, G., Civerolo, E.L., Jernstedt, J., Re, E.B., Buzayan, J. Reaction of Chenopodium quinoa plants to infiltrated Xylella fastidiosa. Phytopathology. 2001. v. 91. p. 511. Abstract.
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Progress 10/01/99 to 09/30/00
Outputs
1. What major problem or issue is being resolved and how are you resolving it?
Production losses due to new and emerging bacterial, phytoplasma, fungal and viral diseases of deciduous tree fruits and nuts, grape and strawberry. These include angular leafspot disease of strawberry, grapevine graft-incompatibility, X-disease of cherry, and Phytophthora root and crown rots. Determination disease etiology and epidemiology, development of improved pathogen detection and identification methods, and evaluation of germplasm for resistance to infection and disease developoment. evelopment of effective, economic disease management strategies without reliance on the use of chemical pesticides, including evelopment, evaluation and implementation of biological and cultural practices alternatives to soil fumigation with methyl bromide to manage soilborne diseases of these crops.
2. How serious is the problem? Why does it matter?
Several biotic and abiotic diseases cause significant production losses for deciduous tree fruit and nut, grape and strawberry growers. However, the etiologies of many of these are unknown or poorly understood. This precludes development of improved biologically-based disease management strategies that do not rely on the use of chemical pesticides. Chemical pesticides, ncluding methyl bromide, threaten worker and consumer safety, as well as environmental quality. Some of these diseases (e.g. angular leafspot disease of strawberry) are of quarantine significance, and affect the export of plant material from California. Use of methyl bromide for soil fumigation to control soilborne pathogens, such as Phytophthora root and crown rots, is being phased out. Due to their different speciation, several of the phylloxera B-resistant rootstocks widely used in California grape plantings are hypesensitive to unknown graft-transmissible agents.
3. How does it relate to the National Program(s) and National Component(s)?
The research is related to NP 303, Plant Diseases (70%) and NP 308, Methyl Bromide Alternatives (30%). The overall purpose of the research is to provide new information regarding the etiology and epidemiology of biotic diseases of deciduous tree fruits and nuts, grape and strawberry in order to develop improved, economic, safe, environmentally sound disease management strategies based on reliable pathogen detection and identification, and genetic and cultural practices.
4. What were the most significant accomplishments this past year?
A. Single Most Significant Accomplishment During FY 2000 Year: A new closterovirus in grapevines was identified and characterized, and a RT-PCR protocol for its detection and identification was developed. This research was performed as part of ongoing work to determine the nature of grapevine graft- incompatibility and identify the etiological agent(s) involved. Infected scions of wine and table grapes cultivars propagated on specific rootstocks grow oorly and decline rapidly. B. Other Significant Accomplishment(s), if any: Completed screens of Paradox walnut seed families for resistance to Phytophthora citricola. This research was conducted as part on ongoing work to developed integrated strategies to effectively manage soilborne diseases of walnut including host resistance. Determined that materials that induce systemic acquired resistance are effective in reducing angular leafspot disease in fruit production fields, as well as in nurseries. This research was conducted as part
of ongoing work to develop effective management of angular leafspot disease based on activation of inherent defense mechanisms in strawberry plants. C. Significant Accomplishment/Activities that Support Special Target Populations: None.
5. Describe the major accomplishments over the life of the project including their predicted or actual impact.
Determined that systemic fertilizer/fungicide strongly suppresses development of lethal Phytophthor cankers on almond trees. This is a potential short-term solution for a major source of tree loss for several Kern County growrs. Completed nursery graft compatibility trials for walnuts graafted onto wingnut rootstock. Selected compatible walnut-wingnut combinations were used to establish field blocks at UCD and in commercial orchards for further evaluation for compatibility, tree growth, and resistance to Phytophthora cinnamomi. Clones of Paradox walnut seed families with reistance to Phytophthora citricola were provided to a commercial nursery for further increase and rooting. The rate of spread of cherry leafroll virus (CLRV), the causal agent (CLRV-W) of walnut blackline disease to, and among, 2 walnut cultivars in California was determined. The effects of CLRV infection on growth and production (yield and quality) of walnuts in California were determined. The comparative
effects of different rootstocks on growth and production of English walnuts in California were determined. The relationship of CLRV-W in California to other CLRV-W strains in Europe based on homology of genomic coat protein sequences was determined. A PCR assay for CLRV-W detection in naturally infected walnut trees was developed. A bioassay for improved detection and identification of Xf based on inoculation of detached strawberry leaves from greenhouse-grown plants was developed. PCR protocols were evaluated and adapted to detect and identify Xf in symptomatic and asymptomatic clinical strawberry field samples. The comparative genomic fingerprinting of several California Xf strains by BOX-, ERIC- and REP-PCR was characterized. Xf- resistant and -susceptible germplasm among commercial strawberries grown in California were identified. Two different graft-transmissible agents have been detected in grapevines based on differential responses of various grape rootstocks. These
findings will allow nurserymen to prescreen scion sources to determine the health of selected rootstocks in the grapevine certification program.
6. What do you expect to accomplish, year by year, over the next 3 years?
During FY2001, SAR inducers other than Actigard to protect strawberry plants from infection by Xf will be identified and evaluation of the effects of these on ALSD development will be initiated. Development of technology to detect and identify Xf in planting stock for use in international quarantines and regulation will be completed. Evaluate canopy of grapevine rootstock trial plants (established in FY2000) for symptoms that might be associated with graft-incompatiblity caused by graft-transmissible agents. During FY2002, evaluation of SAR inducers on ALSD development in strawberry nurseries and fruit production fields will continue. During FY2003, evaluation of SAR incuders on ALSD development in strawberry nurseries and fruit production fields will be completed. Selected grapevines in the rootstock trial established in FY2000) will be destructively sampled and the woody cylinders examined for wood markings, and recollect selected inoculum sources for graft-transmissible agent
identification. During FY2003, evaluation of SAR inducers on ALSD development in strawberry nurseries and fruit production fields will be completed. Identify and characterize graft-transmissible agents in selected grapevine inoculum sources.
7. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end user (industry, farmer, other scientists)? What are the constraints if known, to the adoption & durability of the technology product?
Knowledge that Red Globe decline and death occurred on 4 of 9 rootstocks has provided grape nurseries with the ability to be more selective in choosing rootstocks to minimize the potential impact of this decline problem. Tree removal and timely insecticide application allow cherry growers to economically manage X-disease. Information to exploit genetic alternatives to chemical pesticides has been made available to the California strawberry industry and the UC strawberry breeding program to control fungal (e.g., Phytophthora spp.) and bacterial (e.g. Xanthomonas fragariae) diseases of strawberry. Detection and identification of Xanthomonas fragariae clinical strawberry samples based on biological and molecular techniques has been provided to strawberry nurserymen and growers, private diagnostic laboratories, and regulatory personnel. Other science and technology related to the etiology and epidemiology of diseases of deciduous tree fruits and nuts, grape and strawberry to end
users, such as growers, producers, regulatory agencies, and scientists will be made available over the next several years. The major contraints in developing and adopting effective, economic, safe environmentally-sound strategies to manage diseases of deciduous tree fruits and nuts, grape and strawberry are lack of comprehensive understanding of the etiology and epidemiology of existing and emerging disease, lack of knowledge about the biology of the pathogens that cause these diseases, rapid and reliable pathogen detection and identification methods, and long-term evaluation of the technology developed.
8. List your most important publications in the popular press (no abstracts) and presentations to non-scientific organizations and articles written about your work (NOTE: this does not replace your peer-reviewed publications which are listed below)
None
Impacts
(N/A)
Publications
- Rowhani, A., Zhang,Y.-P., Chin, J., Minafra, A., Golino, D.A., Uyemoto, J.K. Grapevine Rupestris stem pitting associated virus: Population diversity, titerin the host, and possible transmission vector. Proceedings 13th Meeting of the International Council for Virus and Viruslike Diseases of Grapevines. Mar 2000. p. 37.
- Rowhani, A., Zhang, Y.-P., Golino, D.A., Uyemoto, J.K. Isolation and partial characterization of two new viruses from grapevine. Proceedings 13th Meeting of the International Council for Virus and Viruslike Diseases of Grapevines. Mar 2000. p. 82.
- Uyemoto, J.K., Rowhani, A.,Luvisi, D. An association of rootstock stem lesions in Vitis species and different graft- transmissible agents. Proceecings 13th Meeting of the International Council for Virus and Viruslike Diseases of Grapevines. Mar 2000. p. 83-84.
- Westphal, A., Browne, G.T., Schnieder, S. Development of a bioassay to characterize grape replant problem. Phytopathology. 2000. V. 90. Absrtact p. S83.
- Zhang, Y.-P., Kirkpatrick, B.C., DiTerlizzi, B., Uyemoto, J.K. Comparison of cherry green ring mottle virus strains using RT-PCR and coat protein sequence phylogeny. Journal of Plant Pathology. 2000. v. 82. p. 49-53.
- Darjean, D.H., Civerolo, E.L., Kirkpatrick, B.C. In vitro growth inhibition of Xylella fastidiosa by selected metallic plant micronutrients and antibiotics. Phytopathology. 2000. V. 90. Abstract p. S17.
- Garcia, M.R.C., Civerolo, E.L. Culturable endophytic bacteria in strawberry plants. Phytopathology. 2000. V. 90. Abstract p. S16.
- Browne, G.T., Becherer, H.E. Relative resistance to Phytophthora spp. among some rootstocks for almond. Phytopathology. 2000. V.90. Abstract p. S10.
- Browne, G.T., Viveros, M. Chemical management of lethal Phytophthora cankers on almond. Phytopathology. 2000. V. 90.Abstract p. S10.
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