UTILIZATION OF ULTRAVIOLET-C (UV-C) IRRADIATION ON ORNAMENTAL PLANTS FOR DISEASE SUPPRESSION AND GROWTH REGULATION

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1007419
• Project Start Date: Sep 4, 2015
• Project End Date: Aug 31, 2018
• Program Code: [(N/A)]- (N/A)

Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853

Performing Department
Horticultural Research Lab

Non Technical Summary
Plants use sunlight for photosynthesis and are exposed to the ultraviolet (UV) radiation that is present in sunlight. UV radiation is divided into 3 classes: UV-C, UV-B, and UV-A. The Ultraviolet-C (UV-C) region of the UV spectrum includes wavelengths below 280 nm; these highly energetic wavelengths are absorbed by ozone and are not present in the sunlight at the earth's surface. Under normal growing conditions, effects of UC-C light are not seen on plants.UV-C irradiation has been successfully used in the food industry as an environmentally-friendly and safe defense-inducible biological elicitor for meats and horticultural products such as juices, fruits, and vegetables. Very recent research from Europe has demonstrated very promising uses of UV-C to suppress diseases in ornamental plants, to extend postharvest life of cut flowers, and as a pre-harvest treatment, to make plants flower quicker and grow with increased fresh mass and lateral branching.The objective of this project is to determine the effects of ultraviolet-C irradiation (UV-C) on commercially-valuable greenhouse ornamental plants with specific interest in disease suppression, growth (height/branching/fresh weight) regulation, and postharvest longevity.Impact on the Industry: The use of UV-C irradiation is a low-cost technique that is easy to apply to plants. It has already been shown to be a defense-inducible biological elicitor in horticultural products that can extend the postharvest vase life of cut flowers, suppress attack from natural diseases such as Botrytis cinerea, Penicillium expansum, and other plant pathogens, and act as a natural growth regulator. The impact of applying this technology to whole plants would be a world-class breakthrough for the floriculture industry. It will save time and money, and it will have tremendous benefits for the environment by reducing pesticide applications to plants and decreasing the need for plant growth regulators. This is a novel and sophisticated, low-cost technique that can be a sustainable and environmentally-friendly.

Animal Health Component

50%

Research Effort Categories

Basic

(N/A)

Applied

50%

Developmental

50%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
205	2122	1020	50%
205	2123	1020	50%

Knowledge Area
205 - Plant Management Systems;

Subject Of Investigation
2123 - Bedding/garden plants; 2122 - Potted plants;

Field Of Science
1020 - Physiology;

Keywords

ultraviolet light

floriculture

greenhouses

plant growth regulator

environmental

green

Goals / Objectives
The objective of this project is to determine the growth effects that ultraviolet-C irradiation (UV-C) has on commercially-valuable greenhouse ornamental plants. Specific areas of interest include the use of UV-C irradiation for insect reduction or elimination from plants and disease suppression from pathogens such as Botrytis and Powdery Mildew. In addition, the effects of UV-C on plant growth regulation will be determined; specific growth effects include height reduction, increased branching, and flower stimulation. The determination of successful dosages on plants will reduce or eliminate the need for growth retardants. Finally, UV-C light will be studied to determine if increased postharvest longevity of cut flowers is possible by killing bacteria and other pathogens that prevent water uptake in the stem.

Project Methods
Germicidal, low-pressure vapor UV lamps with a nominal power output of 30 W and peak wavelength emission of 253 nm will be applied to the test plants. The dosage rate of the light is measured using a Multi-Sense optical radiometer. Pansies, impatiens, scarlet sage, petunias and other common annual bedding plants will be evaluated by placing plants at various distances below the lamps and applying the UV-C treatments for different times: 5, 15, 30, 60, and 90 minutes. UV-C irradiation will be applied weekly at different dosages for up to 8 weeks. Non-irradiated plants will be used as controls. Growth and flowering responses will be evaluated by recording the number of days to first inflorescence, number of inflorescences, and plant height (cm) every week. The number of lateral stems will be recorded when the plant reaches anthesis as well as fresh weights and dry weights of the plants. Vase-life and flower quality assessments will be made to several different types of common cut flower such as gerberas, alstroemerias, roses, carnations, and zinnias. The germicidal effect of UV-C irradiation on Botrytis cinerea conidial germination and Powdery Mildew growth will also be evaluated. Plants infected with aphids and whiteflies will also be subjected to UV-C treatments to determine if their populations can be suppressed or eliminated without damaging the plants.Bedding PlantsPansies, impatiens, scarlet sage, petunias and other common annual bedding plants will be evaluated by placing plants at various distances below the lamps and applying the UV-C treatments for different times: 5, 15, 30, 60, and 90 minutes. UV-C irradiation will be applied weekly at different dosages for up to 8 weeks. Non-irradiated plants will be used as controls. Growth and flowering responses will be evaluated by recording the number of days to first inflorescence, number of inflorescences, and plant height (cm) every week. The number of lateral stems will be recorded when the plant reaches anthesis as well as fresh weights and dry weights of the plants.Potted PlantsRooted cuttings, 15-20 cm in height, of Pelargonium x hortorum (Geranium), Impatiens wallerana (Impatiens), Chrysanthemum x morifolium (Garden Mum), and Euphorbia pulcherrima (Poinsettia) will be obtained at the beginning of each experiment. The cuttings will be transplanted into larger pots and grown at the Cornell University's South Campus greenhouses at the Long Island Horticulture Research & Extension Center in Riverhead, NY under normal watering and fertilizer systems. The potted plants will be arranged on expanded metal, aluminum benches in the greenhouses in a randomized complete block design. Six to eight replications per species will be used per crop cycle with at least 2 year replications (i.e., replicate trials).For the UV-C irradiation treatments, germicidal low-pressure vapor UV lamps (Osram HNS OFR) will be assembled as described above. The dose rate will be measured prior to each irradiation treatment, at room temperature (~ 25°C) as previously described. UV-C treatments will be administered by placing plants 20-30 cm below the lamps. UV-C irradiation will be applied weekly at the doses from 0 to 10.0 kJ m-2. Plants will receive multiple UV-C treatments in total until they reached the standard commercial size. Non-irradiated plants will be used as controls.Growth and flowering responses will be evaluated from phenotypic observations over a minimum 7-week cultivation period. The number of days to first inflorescence, number of inflorescences, and plant height (cm) will be recorded every week or at the termination of the treatment and experiment. The number of lateral stems will be recorded when the plant reaches anthesis. Fresh weight of the upper parts of the plants (i.e. stems, leaves and inflorescences) will be recorded with a digital balance. The same plant parts will be oven dried at 75°C for 72 h and dry weights will be recorded as necessary.Cut FlowersVase-life and flower quality assessments will be made to several different types of common cut flower varieties. Flowers from gerberas, alstroemerias, roses, carnations, and zinnias will be tested. Cut flowers will be irradiated with 0.5, 1.0, 2.5, 5.0 or 10.0 kJ m−2 UV-C or left non-irradiated and used as controls. Individual flowers will be placed vertically in 1 L glass vases containing 250 ml deionized water (DI). Flower heads will be positioned in parallel and 30 cm below the lamps.After irradiation, the flowers will be held inside a controlled environment chamber running at 20 ± 1 °C, 60 ± 10% R.H. and a 12 h photoperiod (18 μmol m−2 s−1 fluorescent light) in a randomized complete block design. Ten replicate flowers per treatment for each cultivar will be used. Vase-life, stem break, change in flower fresh weight, and water uptake of both the irradiated and non-irradiated (control) flowers will be recorded. Vase-life will be terminated when florets start to senesce and change color or when stems bend over 90°. Stem breakage (stems bending over 90°) will be evaluated both in the number of days and as a percentage (%) of the total flower number. Flower fresh weight (F.W.) will be calculated as the percentage of the initial F.W. value and water uptake (calculated as ml g−1 F.W.) measured every 2 days from day 0 by respectively weighing the stems and the vases (vase + content) on a digital balance.Effect of UV-C on Diseases and InsectsThe germicidal effect of UV-C irradiation on Botrytis cinerea conidial germination will also be evaluated. Plants infected with aphids and whiteflies will also be subjected to UV-C treatments to determine if their populations can be suppressed or eliminated without damaging the plants. Plants infested with aphids and whiteflies will be subjected to various levels of UV-C light for various time periods. Plants will be assessed for health after the treatments, as well as for rate of infection.All experiments will be set up as completely randomized block designs or factorial designs and data will be subjected to one- or two-way ANOVA. Means will be separated using Fisher's LSD multiple range test at P = 0.05. Statistical analysis will be performed.

Progress 09/04/15 to 08/31/18

Outputs
Target Audience:Floriculture and greenhouse industries Ornamental plant industries Members of the Green Industries Members of the Cornell Gardeners and other homeowners Long Island Flower Growers Association (LIFGA) Long Island Nursery and Landscape Association (LINLA) Nassau Suffolk Landscape Growers Association (NSLGA) New York State Flower Industries (NYSFI) Long Island Arborists Association (LIAA) Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project has provided training to undergraduate and graduate students and technical staff, as well as the principal investigator. Student interns from other universities and students from Cornell University have worked on this project and have gained valuable training and experience with a new, innovative technology. How have the results been disseminated to communities of interest?Results have been disseminated by a presentation at an international scientific meeting, the International Society for Horticultural Science (ISHS), seminars, educational programs, and extension/outreach activities. The horticultural industry in the state of New York and its stakeholders have been informed at twilight meetings, open houses, and field days, mostly through their association with Cornell University's Long Island Horticultural Research & Extension Center. They became aware of the research through these activities and were able to comment on the research. Specific to this project, members of the Long Island Flower Growers Association and the Greenhouse Program Working Team (GHPWT) were involved. They were asked to participate in the design and evaluation of the research. These individuals, as well as participants of our advisory committees, contributed to the evaluation process. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? There are several positive and significant impacts that the success of this novel technology can have on the green industry. UV-C irradiation is a low-cost technique that is easy to apply to plants. By using simple light fixtures with special light bulbs, the UV-C can be administered. We have recently demonstrated that this technology has the ability to be used as a natural, environmentally-safe plant growth regulator. UC-C irradiation acts as a natural growth regulator by causing plants to grow with increased fresh mass, shorter height, and lateral branching thus decreasing or eliminating the need for chemical growth retardants, and to make plants flower quicker. The impact of applying this technology to whole plants will be a world-class breakthrough for the green industry. It will save time and money by decreasing, or possibly eliminating, the need for plant growth regulators. It will have tremendous benefits for the environment by reducing growth regulator applications to plants; this will help to reaffirm our industry's commitment to a safer and healthier environment. This is a novel, sophisticated, and inexpensive technique that can be a sustainable and environmentally-friendly tool for the greenhouse production industry in the United States. Other advantages of using UV-C lights include: they can be used under all weather conditions, they can be used anytime, they leaves no residue in the ground or water, there is no problems with drift, there is minimal energy use, it is a more accurate, localized application than chemicals, and UV-C lights are approved as organic. Some of the discoveries (accomplishments) that we have made with this research: 1. It is important to understand that dosage rates of UV-C light are critical. If too high a dosage of UV-C irradiation is used, it will burn plants. It is clear that too high a dosage will damage or kill plants. If too low dosage is used, it will have no effect. 2. By using UV-C light under proper, greenhouse conditions, it can decrease plant height. At appropriate dosage rates, UV-C light can decrease plant height on some species. With African marigolds, pansies, and red salvia, the UV-C irradiation has affected the height of the plants. 3. UV-C light can increase branching in some plants while reducing final, plant height. At appropriate dosage rates, UV-C light can increase branching on some plant species. This effect avoids the need to pinch plants and to apply plant growth regulators. Delayed flowering can also be observed on UV-C treated plants. 4. Depending on the crop, UV-C light can either delay flowering or cause earlier flowering. Depending on the plant species and the dosage rate, UV-C light can either delay flowering or cause earlier flowering. Pansy plants show faster flowering when treated with UV-C light. However, in some plant species, UV-C light delays flowering. Salvia splendens flowering was delayed by UV-C treatment. If the intensity of UV-C light is too great, flowering will also be delayed.

Publications

• Type: Other Status: Published Year Published: 2018 Citation: Bridgen, M. and S. Halliwell. 2017. Evaluation of herbaceous perennial plants on Long Island. 2017 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #90. Pg 32.
• Type: Other Status: Published Year Published: 2018 Citation: Nor Hisham Shah, N.K.A. and M. Bridgen. 2017. In vitro procedures for the development of new Vitex. 2017 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #90. Pg 47.
• Type: Other Status: Published Year Published: 2018 Citation: Bridgen, M. 2017. Asparagus variety trials. 2017 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #90. Pg 64.
• Type: Other Status: Published Year Published: 2018 Citation: Bridgen, M. and N. Mattson. 2017. Comparisons of controlled release fertilizers to traditional fertilizers on the growth of field asparagus. 2017 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #90. Pp. 64-65.
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Nor Hisham Shah, N.K.A. and M. Bridgen. 2018. Inducing mutations in vitro of the Chaste Tree, Vitex agnus-castus, with the herbicide, Oryzalin (Surflan). Combined Proceedings International Plant Propagator's Society. Vol. 68.
• Type: Journal Articles Status: Submitted Year Published: 2019 Citation: Aros, D., M. Suazo, C. Rivas, P. Zapata, C. �beda, and M. Bridgen. 2019. Characterization of new hybrids of Alstroemeria originated from A. caryophylleae scented lines. Under review.
• Type: Book Chapters Status: Published Year Published: 2018 Citation: Bridgen, M.P. 2018. Plant Tissue Culture Techniques for Breeding. In: Johan Van Huylenbroeck, (Ed). Handbook of Plant Breeding: Ornamental Crops. Springer Publishers. Vol 11: 127-144.
• Type: Book Chapters Status: Published Year Published: 2018 Citation: Bridgen, M.P. 2018. Breeding Alstroemeria. In: Johan Van Huylenbroeck, (Ed). Handbook of Plant Breeding: Ornamental Crops. Springer Publishers. Vol 11: 231-236.
• Type: Other Status: Published Year Published: 2018 Citation: Bridgen, M. A. Ulinski, and Sean Halliwell. 2017. Propagation of hybrid Alstroemeria. 2017 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #90. Page 30
• Type: Other Status: Published Year Published: 2018 Citation: Bridgen, M. 2017. Use of Ultraviolet-C (UV-C) radiation on ornamental plants for growth regulation. 2017 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #90. Pp. 30-31.
• Type: Other Status: Published Year Published: 2018 Citation: Bridgen, M. and M. Daughtrey. 2017. Breeding for downy mildew resistance in Impatiens walleriana. 2017 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #90. Pp. 31-32.

Progress 10/01/15 to 09/30/16

Outputs
Target Audience:Floriculture and greenhouse industries Ornamental plant industries Members of the Green Industries Members of the Cornell Gardeners and other homeowners Long Island Flower Growers Association (LIFGA) Long Island Nursery and Landscape Association (LINLA) Nassau Suffolk Landscape Growers Association (NSLGA) New York State Flower Industries (NYSFI) Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project has provided training to undergraduate and graduate students and technical staff, as well as the principal investigator. Student interns from other universities and students from Cornell University have worked on this project and have gained valuable training and experience with a new, innovative technology. How have the results been disseminated to communities of interest?Results have been disseminated by a presentation at an international scientific meeting, the International Society for Horticultural Science (ISHS), seminars, educational programs, and extension/outreach activities. The horticultural industry in the state of New York and its stakeholders have been informed at twilight meetings, open houses, and field days, mostly through theirassociation with Cornell University's Long Island Horticultural Research & Extension Center. They became aware of the research through these activities and were able to comment on the research. Specific to this project, members of the Long Island Flower Growers Association and the Greenhouse Program Working Team (GHPWT) were involved. They were asked to participate in the design and evaluation of the research. These individuals, as well as participants of our advisory committees, contributed to the evaluation process. What do you plan to do during the next reporting period to accomplish the goals?Growth and flowering responses will continue to be evaluated from phenotypic observations over a 4-7 week cultivation period. The number of days to first inflorescence, number of inflorescences, and plant height (cm) will be recorded every week or at the termination of the treatment and experiment. The number of lateral stems will be recorded when the plant reaches anthesis. Fresh weight of the upper parts of the plants (i.e. stems, leaves and inflorescences) will be recorded with a digital balance. The same plant parts will be oven dried at 75°C for 72 h and dry weights will be recorded as necessary. Several species of plants will receivelow dosages of UV-C irradiation for different time periods (15 minutes, 30 minutes, 45 minutes, and 60 minutes), at different frequencies (daily and weekly), and at different dosages. The dosage of UV-C irradiation will bemeasured in kJ/m2. The time of application and the distance from the lamp are two considerations when applying UV-C irradiation. Similar dosage rates can be accomplished by placing the plant closer to the UV-C light for shorter periods of time or farther from the UV-C light for longer periods of time. Because dosage rate controls the effect on the plant growth, determining the best dosage rate by the most appropriate procedure (time vs. distance) is one of the challenges of this research.

Impacts
What was accomplished under these goals? 1. Dosage rates are critical Too high a dosage of UV-C irradiation will burn plants and too low will have no effect. It is clear that too high a dosage will damage or kill plants. 2. UV-C light can decrease plant height At appropriate dosage rates, UV-C light can decrease plant height on some species. With African marigolds, pansies, and red salvia, the UV-C irradiation has affected the height of the plants. 3. UV-C light can increase branching At appropriate dosage rates, UV-C light can increase branching on some plant species. This effect avoids the need to pinch plants and to apply plant growth regulators. Delayed flowering is also obvious on UV-C treated plants. 4. UV-C light can either delay flowering or cause earlier flowering Depending on the plant species and the dosage rate, UV-C light can either delay flowering or cause earlier flowering. Pansy plants show faster flowering when treated with UV-C light. However, in some plant species, UV-C light delays flowering. Salvia splendens flowering was delayed by UV-C treatment. If the intensity of UV-C light is too great, flowering will also be delayed.

Publications

• Type: Journal Articles Status: Published Year Published: 2017 Citation: Miller, C.T., K. Snyder, and M.P. Bridgen. 2017. The 2017 National Floriculture Forum: Engaging young people in the industry. HortTechnology 27(6):754-756
• Type: Theses/Dissertations Status: Published Year Published: 2017 Citation: Nor Hisham Shah, N.K.A. 2017. Micropropagation and in vitro mutagenesis of Vitex agnus-castus. M.S. thesis. Cornell University.
• Type: Book Chapters Status: Accepted Year Published: 2018 Citation: Bridgen, M.P. 2018. In vitro systems for ornamental plant breeding. IN: Handbook of Plant Breeding: Ornamental Crops. Springer Publishers.
• Type: Book Chapters Status: Accepted Year Published: 2018 Citation: Bridgen, M.P. 2018. Breeding Alstroemeria. IN: Handbook of Plant Breeding: Ornamental Crops. Springer Publishers.
• Type: Websites Status: Published Year Published: 2017 Citation: www.LongIslandHort.cornell.edu
• Type: Other Status: Published Year Published: 2017 Citation: Bridgen, M.P. 2016. Breeding of hybrid Alstroemeria. 2016 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #. Pp. 30.
• Type: Other Status: Published Year Published: 2017 Citation: Bridgen, M.P. 2016. Use of Ultraviolet-C (UV-C) radiation on ornamental plants for growth regulation. 2016 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #. Pp. 30-31.
• Type: Other Status: Published Year Published: 2017 Citation: Bridgen, M.P. 2016. International educational and extension program for the greenhouse industry. 2016 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #. Pp. 31-32.
• Type: Other Status: Published Year Published: 2017 Citation: Keach, J., M. Bridgen, and M.L. Daughtrey. 2016. Breeding for downy mildew resistance in Impatiens walleriana. 2016 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #. Pp. 32.
• Type: Other Status: Published Year Published: 2017 Citation: Bridgen, M.P. and C. Nalty. 2016. Evaluation of herbaceous perennial plants on Long Island. 2016 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #. Pp. 32.
• Type: Other Status: Published Year Published: 2017 Citation: Bridgen, M.P. and N. Mattson. 2016. Comparisons of controlled release fertilizers to traditional fertilizers on the growth of field asparagus. 2016 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #. Pp. 65-66.
• Type: Other Status: Published Year Published: 2017 Citation: Nor Hisham Shah, N.K.A. and M.P. Bridgen. 2016. In vitro procedures for the development of new Vitex varieties. 2016 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #. Pp. 51-52.
• Type: Other Status: Published Year Published: 2017 Citation: Bridgen, M.P.. 2016. Asparagus variety trials. 2016 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #. Pp. 65.

Progress 09/04/15 to 09/30/15

Outputs
Target Audience:Floriculture and greenhouse industries; Ornamental plant industries; Members of the Green Industries; Members of the Cornell Gardeners and other homeowners; Long Island Flower Growers Association (LIFGA); Long Island Nursery and Landscape Association (LINLA); Nassau Suffolk Landscape Growers Association (NSLGA); New York State Flower Industries (NYSFI); extension and outreach; formal classroom instructions, laboratory instructions; internships; workshops. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project has provided training opportunities to students and technical staff, as well as the principal investigator. Student interns from other universities and students from Cornell University have worked on this project and have gained valuable training and experience with a new, innovative technology. How have the results been disseminated to communities of interest?The horticultural industry on Long Island is the largest in the state of New York and its stakeholders have interacted through their association with Cornell University's Long Island Horticultural Research & Extension Center. Stakeholders were engaged in this project through open houses, field days, and educational programs. They became aware of the research through these activities and were able to comment on the research. Specific to this project, members of the Long Island Flower Growers Association and the Greenhouse Program Working Team (GHPWT) were involved. They were asked to participate in the design and evaluation of the research. These individuals, as well as participants of our advisory committees, contributed to the evaluation process. Later, when commercial implementation begins, these stakeholders will be involved. What do you plan to do during the next reporting period to accomplish the goals?Pansies, impatiens, scarlet sage, petunias and other common annual bedding plants will be evaluated by placing plants at various distances below the lamps and applying the UV-C treatments for different times: 5, 15, 30, 60, and 90 minutes. UV-C irradiation will be applied weekly at different dosages for up to 8 weeks. Non-irradiated plants will be used as controls. Growth and flowering responses will be evaluated by recording the number of days to first inflorescence, number of inflorescences, and plant height (cm) every week. The number of lateral stems will be recorded when the plant reaches anthesis as well as fresh weights and dry weights of the plants. Growth and flowering responses will be evaluated from phenotypic observations over a minimum 7-week cultivation period. The number of days to first inflorescence, number of inflorescences, and plant height (cm) will be recorded every week or at the termination of the treatment and experiment. The number of lateral stems will be recorded when the plant reaches anthesis. Fresh weight of the upper parts of the plants (i.e. stems, leaves and inflorescences) will be recorded with a digital balance. The same plant parts will be oven dried at 75°C for 72 h and dry weights will be recorded as necessary.

Impacts
What was accomplished under these goals? This research was reported at the 2016 International Society for Horticultural Sciences (ISHS) symposium on lighton May 23, 2016.Several species of greenhouse plants received low dosages of UV-C irradiation for different time periods (15 minutes, 30 minutes, 45 minutes, and 60 minutes), at different frequencies (daily and weekly), and at different dosages. The dosage of UV-C irradiation was measured in kJ/m2. The time of application and the distance from the lamp are two considerations when applying UV-C irradiation. Similar dosage rates can be accomplished by placing the plant closer to the UV-C light for shorter periods of time or farther from the UV-C light for longer periods of time. Because dosage rate controls the effect on the plant growth, this research is determining the best dosage rate by the most appropriate procedure (time vs. distance) for several plant species. 1. Dosage rates are critical Too high a dosage of UV-C irradiation will burn plants and too low will have no effect. It is clear that too high a dosage will damage or kill plants. 2. UV-C light can decrease plant height At appropriate dosage rates, UV-C light can decrease plant height on some species. With African marigolds, pansies, and red salvia, the UV-C irradiation has affected the height of the plants. 3. UV-C light can increase branching At appropriate dosage rates, UV-C light can increase branching on some plant species. This effect avoids the need to pinch plants and to apply plant growth regulators. Delayed flowering is also obvious on UV-C treated plants. 4. UV-C light can either delay flowering or cause earlier flowering Depending on the plant species and the dosage rate, UV-C light can either delay flowering or cause earlier flowering. Pansy plants show faster flowering when treated with UV-C light. However, in some plant species, UV-C light delays flowering. Salvia splendens flowering was delayed by UV-C treatment. If the intensity of UV-C light is too great, flowering will also be delayed.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Keach,J.E., Daughtrey, M.L., Bridgen, M.P. and Salgado, C. 2016. Susceptibiiity of impatiens species to downy mildew caused by Plasmopara obducens. In A. Gover (Ed.). Proc. Northeast. Plant, Pest, Soils Conf. 1:106.
• Type: Theses/Dissertations Status: Published Year Published: 2016 Citation: Keach, J.E. 2016. Screening and breeding Impatiens for downy mildew resistance. Ph.D. dissertation. Cornell University. 116 pages.
• Type: Books Status: Published Year Published: 2016 Citation: Bridgen, M.P., Editor. 2015 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #88. 108 pages.
• Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Keach, J.E. and M.P. Bridgen. 2015. Screening and breeding impatiens for downy mildew resistance. Combined Proceedings of the International Plant Propagators Society. Vol. 65.
• Type: Book Chapters Status: Published Year Published: 2016 Citation: Pennetti, V. and M. Bridgen. 2015. In vitro micropropagation and mutation of clover, Trifolium amoenum. IN: M.P. Bridgen (ed.) 2015 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #88. Page 31.
• Type: Book Chapters Status: Published Year Published: 2016 Citation: Bridgen, M. and M. Figueroa. 2015. Breeding of hybrid Alstroemeria. IN: M.P. Bridgen (ed.) 2015 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #88. Pp. 31-32.
• Type: Book Chapters Status: Published Year Published: 2016 Citation: Bridgen, M. and C. Nalty. 2015. Evaluation of herbaceous perennial plants on Long Island. IN: M.P. Bridgen (ed.) 2015 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #88. Page 32.
• Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Nor Hisham Shah, N.K.A. and M.P. Bridgen. 2015. Seed germination studies of Vitex agnus castus. Combined Proceedings of the International Plant Propagators Society. Vol. 65.
• Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Pennetti, V. and M.P. Bridgen. 2015. Traditional and in vitro development of new clover (Trifolium spp.) plants. Combined Proceedings of the International Plant Propagators Society. Vol. 65.
• Type: Book Chapters Status: Published Year Published: 2016 Citation: Bridgen, M. 2015. Use of Ultraviolet-C (UV-C) radiation on ornamental plants for growth regulation. IN: M.P. Bridgen (ed.) 2015 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #88. Page 30.
• Type: Book Chapters Status: Published Year Published: 2016 Citation: Keach, J. and M. Bridgen. 2015. Breeding and development of downy mildew resistance in Impatiens walleriana IN: M.P. Bridgen (ed.) 2015 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #88. Pp. 30-31.
• Type: Book Chapters Status: Published Year Published: 2016 Citation: Daughtrey, D., J. Keach, L. Hyatt, M. Bridgen and C. Salgado. 2015. Downy mildew on impatiens: susceptibility of different impatiens species. IN: M.P. Bridgen (ed.) 2015 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #88. Page 41.
• Type: Book Chapters Status: Published Year Published: 2016 Citation: Nor Hisham Shah, N.K.A. and M. Bridgen. 2015. In vitro procedures for the development of new Vitex varieties. IN: M.P. Bridgen (ed.) 2015 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #88. Page 52.
• Type: Book Chapters Status: Published Year Published: 2016 Citation: Bridgen, M. 2015. Asparagus variety trials. IN: M.P. Bridgen (ed.) 2015 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #88. Pp. 64-65.
• Type: Book Chapters Status: Published Year Published: 2016 Citation: Bridgen, M. and N. Mattson. 2015. Comparisons of controlled release fertilizers to traditional fertilizers on the growth of field asparagus. IN: M.P. Bridgen (ed.) 2015 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, NY. Horticulture Bulletin #88. Pp. 65-66.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Bridgen, M.P. 2016. Using ultraviolet-C (UV-C) irradiation on greenhouse ornamental plants for growth regulation. Acta Hort. (ISHS) 1134:49-56.