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:
Flowers and flower extracts from susceptible blueberry cultivars increase spore production and appressoria of anthracnose (Colletotrichum acutatum). Preliminary results suggest that extracts from resistant blueberries have no effect on appresoria. This observation may be linked to field resistance to this pathogen. Resistant and susceptible cultivars continue to be tested for effects on spore production and appressoria formation. Genome sequencing of the blueberry pathogen Valdensinia heterodoxa for SSR development was completed. The genome has been assembled and screened for SSRs. Primer design for population studies using SSRs is in progress. Seedless fruit development in blueberry. Further crosses were made to move seedless or low seeded variants between highbush and rabbiteye blueberries. Northern-adapted rabbiteye blueberry selections. Crossing and recombination was done among advanced selections of northern-adapted rabbiteye. Advanced selections were evaluated for cold hardiness and the ability to maintain cold hardiness for an extended period during winter months. Germplasm transfer utilizing blueberry species from Section Hemimyrtillus. Several initial hybrids with species of Section Hemimyrtillus were crossed with commercial blueberries to facilitate transfer of genes to cultivated blueberry. Section Hemimyrtillus species have the traits of extreme vigor, good fruit quality and repeat fruiting. Cranberry genome sequencing. The entire genome of an inbred line of cranberry was sequenced and the sequence has been assembled. Complete annotation is in progress. Strawberry breeding. Superior performance of selection B1033 in multiple environments suggests a possible release in 2012. Postharvest evaluation in egg cartons is logistically more efficient than evaluation in commercial containers. The 2012 performance of ARS repeat-fruiting strawberry selections indicates breeding goals should emphasize selection at the seedling stage for anthracnose resistance and early fruit production in addition to open plant habit and good runner production. Test cross-pollinations were made to determine inheritance of repeat-fruiting genes. Raspberry breeding. Post-harvest fruit evaluation revealed standard room-temperature evaluation is inferior to refrigerated evaluation. The field planting shows virus symptoms years later than predicted, indicating natural selection for virus response may be more effective in regions of high raspberry production. Dwarf plant architecture was identified as a desirable production-efficiency trait by eliminating trellising and reducing pruning and weeding needs. Work was initiated to obtain dwarf, spine-free, fall-fruiting, black raspberries.
1. Generation of the first genetic map of cranberry. Cranberry breeding and selection can be improved with markers associated with key traits. The first step toward that goal is development of a map. ARS researchers from Chatsworth, NJ in conjunction with Rutgers University researchers described and submitted for publication the first map for this important crop species. This map and subsequent versions of it will be used to facilitate marker-assisted selection to improve and accelerate cranberry breeding.
2. Inhibitory activity of alpha-glucosidase in peel and pulp of blueberry. Blueberry cultivars with high alpha-glucosidase inhibitory activity may decrease glucose absorption and may help regulate glucose levels in diabetics. ARS researchers in Chatsworth, NJ and Beltsville, MD assayed the inhibition of alpha-glucosidase activity by peel and pulp of a wide range of blueberry cultivars. Significant differences in alpha-glucosidase inhibitory activity were found both among cultivars, and between peel and flesh. Peel tissue possessed higher levels of inhibitory activity than pulp. Blueberry selections with high alpha-glucosidase inhibition could be used by breeding programs to develop new cultivars with improved health benefits.
3. Antioxidant capacities in peel and pulp tissue of blueberry. Blueberries vary in their antioxidant content between pulp and peel and this information is of considerable interest to those interested in blueberries for their health-promoting properties. The total anthocyanins, total phenolics, and oxygen radical scavenging capacities against peroxyl free radicals, hydroxyl radicals, hydrogen peroxide, and singlet oxygen radicals were evaluated among a wide range of blueberry cultivars. A significant difference in all parameters existed between peel and pulp tissue and among cultivars. Blueberry selections with high anthocyanin and phenolic contents and/or high antioxidant activities could be used by breeding programs to develop new cultivars with improved health benefits.
4. Fertility of northern-adapted rabbiteye blueberry hybrids. Variability in fertility of blueberry varieties can have a negative effect on crop yield. Northern highbush blueberry varieties are regarded as self-fruitful whereas Rabbiteye blueberry varieties are not self-fruitful and require cross-pollination by another variety. ARS researchers in Chatsworth, NJ conducted a fertility and pollination study of Rabbiteye x highbush hybrids that demonstrated northern-adapted rabbiteye hybrids are intermediate to highbush and rabbiteye in their cross-pollination requirements. Sufficient variation existed among the hybrid selections to select clones with self-fertility equivalent to that of highbush blueberry. This is critical cultural information for producers planning to grow these hybrids.Wang, S.Y., Chen, H., Camp, M.J., Ehlenfeldt, M.K. 2011. Flavonoid constituents and their contribution to antioxidant activity in cultivars and hybrids of rabbiteye blueberry (Vaccinium ashei Reade). Food Chemistry. 132:855-864.