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
Repeat/continuous fruiting strawberry. Repeat and continuous fruiting affords new opportunities to increase yield and extend the strawberry production season. Genetic studies identified new genes that influence repeat fruiting. Research on continuous-fruiting revealed differences among strawberry genotypes with regard to light and temperature in high tunnel production systems. The results afford new opportunities for increased strawberry production. Exotic blueberry germplasm. Crop relatives often have valuable genes for cultivar improvement. Blueberry species of Section Hemimyrtillus with extreme vigor, good fruit quality and repeat fall-fruiting were crossed with cultivated blueberry. Progeny will be assessed for development of improved cultivars. This material will benefit blueberry breeders and growers. Blueberry health benefits. Plants contain compounds that benefit human health. We determined that differences in alpha-glucosidase inhibitor activity existed among and between peel and flesh of 58 blueberry cultivars. New cultivars with high alpha-glucosidase inhibitor activity may have potential to decrease glucose absorption and regulate blood glucose level. Raspberry fruit quality. Raspberry fruit have a short shelf life after harvest. We observed that black raspberries have reduced rot compared to red types. This difference may be due to reduced ethylene production. The results will be of value in developing cultivars with longer shelf life. Strawberry/raspberry phytonutrients. Fruit quality is important in developing new strawberry and raspberry cultivars. We measured total antioxidants, phenolics, anthocyanins, titratable acids and soluble solids in strawberry and raspberry cultivars and breeding lines. Strawberry lines with high fruit quality were identified. Black raspberries were higher in all parameters than raspberries of other colors. This information will facilitate further enhancement of fruit quality. Blueberry anthracnose. Anthracnose fungi cause blueberry fruit rot. We determined that blueberry flower extracts increase spore production in infected fruit. Evaluation of resistant and susceptible plants suggests that these extracts may be linked to anthracnose resistance. The results will aide in identifying resistant cultivars for breeders and growers. Cranberry genome. Knowledge of a plants genome facilitates gene discovery and breeding improved cultivars. We sequenced the cranberry genome and are searching it for SSR molecular markers that will be used for breeding and mapping genes of economic importance. The genome sequence will benefit cranberry researchers working to develop improved cranberries. Colletotrichum acutatum genome. Colletotrichum acutatum is a major blueberry and cranberry pathogen. To better combat this pathogen we sequenced its genome. Pathologists will use the sequence to identify disease causing genes and develop strategies to combat disease.
1. Cold-acclimation and deacclimation of blueberry. Cold-acclimation and deacclimation patterns are critical to determining if a blueberry selection is hardy enough to grow in a particular region. ARS researchers at Beltsville, MD, and Chatsworth, NJ, characterized the timing and rate of acclimation and deacclimation in blueberry genotypes with diverse backgrounds. Most southern-adapted selections began to lose their cold hardiness after late December even though mean daily temperatures continued to decrease through the month of January. One northern-adapted rabbiteye selection was identified that maintained its cold hardiness through the first week in February, similar to the behavior of northern highbush blueberries. This extended cold hardiness which we identified in rabbiteye blueberry is a critical breakthrough that will be utilized by plant breeders in developing rabbiteye types with effective northern adaptation.
2. ‘Summer Sunset’ blueberry. There is considerable interest in fruit cultivars that will satisfy both culinary and ornamental needs. In cooperation with a university collaborator, ARS researchers at Chatsworth, NJ, released a new blueberry variety for the home garden market that produces an abundance of multi-colored berries as it ripens with color progressing from yellow-green, to orange-red, to red, to black. ‘Summer Sunset’ exhibits reliable productivity, good yield, early ripening, and medium size fruit. ‘Summer Sunset’ ripens around the time of the early commercial rabbiteye varieties ‘Climax’ and ‘Premier’. A patent has been applied for by the university cooperator and it is expected that this variety will be marketed through retail outlets.
3. Blueberry phytonutrients. Fruit with high phenolic content and high antioxidant activities have significant health benefits. ARS researchers at Beltsville, MD, and Chatsworth, NJ, measured blueberry soluble solids, sugars, organic acids, total anthocyanins and antioxidant activities among species and cultivars and between two growing seasons and found that values varied substantially. The diversity in these fruit quality attributes and antioxidant capacities presents a new opportunity for genetic improvement of blueberries through breeding programs.
4. Strawberry postharvest fruit quality. Strawberry fruit are highly perishable. ARS researchers at Beltsville, MD, determined that, in breeding low-rot strawberries, the evaluation of potential cultivars for percentage rot at harvest cannot substitute for evaluation of percentage rot after harvest and storage in a cooler. Statistical analysis methods were optimized for identifying low-rot cultivars that will be useful to other breeders. Growers will benefit from the finding that rain events were found to increase field, but not postharvest, rot; dry air was found to decrease postharvest, but not field, rot.
5. Methodology for screening for resistance to fungal pathogens in cranberry. Cranberries have numerous fungal pathogens that can attack and rot their fruit. ARS researchers at Chatsworth, NJ, developed a field inoculation method for screening cranberry fruit for resistance to several fungal pathogens. The method will allow rapid screening of breeding selections, and allow breeders to develop cultivars with improved rot resistance.Lewers, K.S., Wang, S.Y., Vinyard, B.T. 2010. Evaluation of blackberry cultivars and breeding selections for fruit quality traits and flowering and fruiting dates. Crop Science. 50(6):2475-2491.