1a. Objectives (from AD-416):
Develop improved cultivars and enhanced germplasm of strawberry, blueberry, and black raspberry that possess desirable horticultural traits, including broad environmental adaptation, disease resistance, longer fruiting season, high yield, and excellent fruit and plant quality characteristics. Develop methodologies to more effectively and precisely identify and select disease-resistant small-fruit genotypes.
1b. Approach (from AD-416):
Small fruit germplasm from established cultivar materials to wild types will be evaluated using both classical and molecular techniques. Scientists will develop improved disease screening methods, identify and evaluate disease resistant germplasm, and develop improved methods of incorporating the resistance into superior germplasm. Genetic aspects of both pathogen and host variation will be studied. Concurrent with selection for disease resistance, breeding will emphasize selection for other factors necessary to the development of successful cultivars, with particular emphasis on fruit quality and phytonutrients, environmental adaptation, and adaptation to mechanization. Vaccinium (blueberry and cranberry) breeding and disease work will be carried out at Chatsworth, New Jersey, and Fragaria (strawberry) and Rubus (blackberry and raspberry equals brambles) work will be carried out at Beltsville, Maryland.
3. Progress Report:
The project was responsible for four new blueberry cultivar releases and a new strawberry cultivar, ‘Flavorfest’, with superior flavor and disease resistance. The project made several advances in the development of small-fruit cultural practices, including the development of specialized summer-fruiting and fall-fruiting production systems for strawberry. The project generated significant advances in small-fruit genetics and pathology, including: generation of the first genetic map of cranberry to facilitate marker-assisted selection to improve and accelerate cranberry breeding; development of a field-inoculation method for screening cranberry fruit for resistance to several fungal pathogens to allow rapid screening of breeding selections; fungal and viral disease research in blueberry and cranberry studying pathogens, sources of resistance, and vectors to facilitate screening and breeding; demonstration that terpenes synthesized by cranberry plants in response insect feeding deter further feeding, and attract predators; demonstration that nurseries are an important source of Blueberry Scorch Virus (BlScV) dissemination; discovery of a new phytoplasma infecting blueberry; and demonstration that fungal DNases can induce non-host resistance in plants. The project made significant advances in small-fruit germplasm development, including: germplasm transfer utilizing the extremely diverse blueberry species of Vaccinium section Hemimyrtillus; studies of cold-acclimation and deacclimation of diverse blueberry selections; demonstration of cold-hardiness transfer into hexaploid germplasm; documentation of high fertility in some selections of northern-adapted rabbiteye blueberry hybrids; and studies of genetic control of parthenocarpy in highbush blueberry and rabbiteye blueberry. The project also conducted numerous studies of small-fruit anti-oxidants, neutraceuticals, and fruit quality, including: studies of strawberry post-harvest fruit quality; studies of fresh-fruit quality in 600 strawberry progenies; evaluations of blueberry fruit quality across numerous rabbiteye and highbush cultivars; evaluations of anti-oxidant enzyme activities among cultivars of rabbiteye blueberries and rabbiteye-hybrid derivatives; evaluations of anti-oxidant capacities and fruit-quality components of forty-two blueberry cultivars across two growing seasons; identification of blueberry cultivars with high individual flavonoid contents; documentation of anti-oxidant capacities and alpha-glucosidase inhibition levels in peel and pulp of blueberry; evaluation of anti-oxidant activity and fruit quality of raspberry; and demonstration that late-flowering blackberries have higher sugar and anti-oxidant levels.
1. ‘Flavorfest’ strawberry cultivar release. Mid-Atlantic strawberry growers face an increasing problem from plant loss and fruit-rot when using the current leading strawberry variety because of its susceptibility to the fungal disease, anthracnose. ‘Flavorfest’ strawberry is resistant to plant and fruit-rot anthracnose, and compared to the current leading variety, has a very similar season, up to a two-fold higher yield, and large berries with excellent flavor and creamy texture. Mid-Atlantic strawberry crop consultants and extension agents are advising growers to try ‘Flavorfest’ and consider it as the replacement for the current leading variety. Because the plasticulture system in the mid-Atlantic requires planting small potted plants instead of bare-root plants, nurseries usually carry only one to three varieties, so that ‘Flavorfest’, if adopted, has the potential to be the leading strawberry variety in eastern strawberry production in a few seasons.
2. Cranberry volatiles provide natural defense to insect attack. Pesticide sprays are often required to control insect pests on crop plants. ARS and Rutgers University scientists demonstrated that when insects feed on American cranberry, the plant produces volatiles that not only deter further feeding, but also attract predators of the insect pest. The results are important for exploiting the natural plant defense response, reducing the need for pesticide application and developing natural protectants for pest control.
3. Induced disease resistance in plants. New strategies are needed to bolster natural plant defenses against fungi that cause plant disease. Ironically, plants are resistant to infection by most fungi and this is termed non-host resistance. We reasoned that better understanding this phenomenon may help us develop strategies to control disease causing fungi. ARS researchers from Chatsworth, NJ in conjunction with a Washington State University researcher showed that fungal enzymes that degrade plant DNA can induce non-host resistance in plants. This mechanism of resistance can be potentially exploited to increase resistance to pathogens that cause disease in plants.
4. A new disease of blueberry. Phytoplasmas are virus-like microorganisms that cause incurable diseases in plants. ARS researchers from Chatsworth, NJ and Beltsville, MD showed that a previously undescribed phytoplasma is responsible for a new disease of blueberry plants in New Jersey. Armed with this new knowledge, scientists can now determine how the disease is spread and devise strategies for plant breeders to develop new cultivars that are resistant to the disease.Georgi, L., Johnson-Cicalese, J., Honig, J., Das, S.P., Rajah, V.D., Bhattacharya, D., Bassil, N.V., Rowland, L.J., Polashock, J.J., Vorsa, N. 2013. The first genetic map of the American cranberry: exploration of synteny conservation and quantitative trait loci. Theoretical and Applied Genetics. 126:673-692.