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United States Department of Agriculture

Agricultural Research Service


Location: Genetic Improvement for Fruits & Vegetables Laboratory

2010 Annual Report

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
Genetic control of parthenocarpy in highbush blueberry. Crosses were completed to evaluate the previously developed genetic model. Crosses were made for more vigorous plant types within this germplasm. Blueberry cultivar screening for scorch virus resistance. Virus transmission by grafting is being used to screen blueberry cultivars for resistance. Over 1000 plants from 100 cultivars have been grafted; thirteen cultivars remain virus-free. Fertilizer regime and disease incidence in blueberry. Preliminary results of a multi-disciplinary study with Rutgers to determine the impact of fertilizer regime on blueberry production and disease incidence suggest that fertilizer impacts both anthracnose fruit rot incidence and Botryosphaeria stem blight incidence. Cranberry fruit rot pathogen taxonomy. The fruit rot pathogen Physalospora vaccinii was examined using morphologic and genetic factors. The pathogen population was found to consist of two distinct species that are currently misclassified. A formal reclassification is in progress. Fruit quality in strawberry. The soluble solids, total phenolics, titratable acidity, and antioxidant activity in strawberry selection B-1033 were higher than in ‘Allstar’, but lower than in ‘Ovation’. Blueberry fruit quality. Evaluations of 42 rabbiteye blueberry cultivars revealed varying fruit qualities. A significant year x cultivar interaction existed for most parameters measured. Antioxidants and fruit quality of raspberry. Anthocyanins, total phenolics, and antioxidant activity of 60 genotypes of raspberry (black, red, purple and yellow) were evaluated. Black fruit were higher in all parameters than were other colors. Fruit quality in strawberry. Strawberry breeding selections were evaluated for two years to determine the best protocols and data-analysis methods to develop cultivars with improved post-harvest quality. “Protected” strawberry production. ARS scientists at Beltsville, MD, and Kearneysville, WV, with scientists at the University of Maryland evaluated several strawberry breeding selections for production in fall and winter in “protected cultivation”. Strawberry production methods. New summer strawberry production methods were evaluated to determine which production factors contribute most to summer yield. Repeat fruiting in strawberry. Scientists evaluated 20,000 strawberry seedlings for two years to determine the number of genes and gene action controlling repeat fruiting. Repeat fruiting in raspberry. Approximately 100 individuals from repeat-fruiting black raspberry test-crosses were evaluated to determine if the gene controlling repeat-fruiting involves the same genomic region as in red raspberry. Fruit quality in raspberry. ARS scientists at Beltsville, MD, with scientists at the University of Maryland, evaluated raspberry selections to determine the best protocols and data-analysis methods to develop cultivars with improved post-harvest quality.

4. Accomplishments
1. New blueberry selection ARS 99-88. New blueberry cultivars are needed to address consumers desire for improved fruit quality. In order to address this need, we released the blueberry selection ARS 99-88 named ‘Sweetheart’. Its desirable characteristics are: superior flavor, very good firmness, good productivity, attractive medium- to medium-large-sized fruit, and early season, concentrated ripening. This variety has been distributed to commercial blueberry nurseries for national distribution.

2. New blueberry selection 11-104. New blueberry cultivars are needed to address consumers desire for improved fruit quality. In order to address this need, we released the blueberry selection 11-104 named ‘Razz’. Its desirable characteristics are: reliable productivity, good yields, midseason ripening, medium to large fruit, medium to light blue fruit color, and excellent flavor with remarkable raspberry overtones. This variety has been distributed to commercial blueberry nurseries for national distribution.

3. Nurseries are an important source of Blueberry Scorch Virus (BlScV) dissemination. BlScV was appearing in newly planted blueberry fields in a pattern atypical for normal spread by the insect vector of this disease. We determined that blueberries propagated at nurseries can be infected with BlScV, but may remain symptomless. The infected plants are then shipped to farms where the virus symptoms appear within the next 2-5 years. This prompted a state-wide nursery inspection system to identify infected source plants and prevent further distribution.

4. Antioxidant capacities among cultivars of rabbiteye blueberry and rabbiteye-hybrid derivatives. The differences in scavenging capacities for free radicals among 42 selected blueberry cultivars were significant. Extracts from fruit of pure rabbiteye had higher levels of scavenging capacity for oxygen radicals capacities compared to rabbiteye-hybrid derivatives (‘Pearl River’, ‘Snowflake’, and ‘Pink Lemonade’) and northern highbush blueberry standards (‘Bluecrop’, ‘Duke’ and ‘Elliott’).

5. Antioxidant activity in rabbiteye blueberry. Extensive variation in antioxidant enzyme activities exists among cultivars of rabbiteye blueberries and rabbiteye-hybrid derivatives. However, this information is not well characterized. We found that rabbiteye blueberry cultivars had varying levels of non-enzyme antioxidant components, such as ascorbic acid, and a wide range of levels of antioxidant enzyme activities. Among 42 cultivars, ‘Early May’ had the highest enzyme activity. This information will be used by blueberry breeders to develop new blueberry cultivars with enhanced nutritive value.

6. Late-flowering blackberries are sweeter and higher in anti-oxidants. ARS researchers at Beltsville, Maryland, compared 122 blackberry cultivars and breeding selections for antioxidant levels, flavor, flowering season, and fruiting season to help farmers and blackberry breeders better select blackberry varieties. In addition to finding a tremendous range for all traits observed, we found that late-flowering blackberries tend to be sweeter and higher in antioxidants.

Review Publications
Wang, S.Y., Millner, P.D. 2009. Effect of Compost Socks System on Antioxidant Capacity, Flavonoid Content, and Fruit Quality of Strawberries. Journal of Agricultural and Food Chemistry. 57:9651-9657.

Wang, S.Y., Chen, C. 2010. Effect of allyl isothiocyanate on antioxidant enzyme activities, flavonoids and fruit quality of blueberry (Vaccinium corymbosum L., cv. Duke). Food Chemistry. 122:1153-1158.

Ehlenfeldt, M.K., Rowland, L.J., Ogden, E.L., Vinyard, B.T. 2009. Cold hardiness of southern-adapted blueberry genotypes and the potential for their use in northern adapted blueberry breeding. Plant Breeding. 128:393-396.

Ehlenfeldt, M.K., Polashock, J.J., Stretch, A.W., Kramer, M.H. 2010. Mummy Berry Fruit Rot and Shoot Blight Incidence in Blueberry: Prediction, Ranking, and Stability in a Long-term Study. HortScience. 45:92-97.

Wang, S.Y., Chen, C., Yin, J. 2010. Effect of allyl isothiocyanate on antioxidants and fruit decay of blueberries. Food Chemistry. 120:199-204.

Ehlenfeldt, M.K., Martin Jr, R.B. 2010. Seed set, berry weight, and yield interactions in highbush blueberry cultivars (Vaccinium corymbosum L.) ‘Bluecrop’ and ‘Duke’. Journal of American Pomological Society. 64:161-170.

Polashock, J.J., Oudemans, P.V., Caruso, F.L., Mcmanus, P., Crouch, J. 2009. Population structure of the North American cranberry fruit rot complex. Plant Pathology. 58:1116-1127.

Last Modified: 08/18/2017
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