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Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/30/2004 Publication Date: 5/1/2006 Citation: Smith, B.J. 2006. USDA-ARS strawberry anthracnose resistance breeding program. Acta Horticulturae 708:-463-470. Interpretive Summary: Anthracnose fruit and crown rots have become important diseases of strawberries worldwide; however, there are few effective fungicides available for control of these diseases. The most effective and environmental sound means of anthracnose control is the use of resistant cultivars. The USDA-ARS Small Fruit Research Station in Poplarville, MS developed a protocol to identify anthracnose resistant strawberry seedlings that is being used in the development of resistant cultivars. Strawberry seed generated by various breeding programs is germinated at Poplarville, and the seedlings are grown for at least three months before inoculation with Colletotrichum acutatum or C. fragariae. After 48 hours incubation in a dew chamber at 100% relative humidity, the plants are grown for 30 days in a warm greenhouse and scored for disease development. Resistant plants are further evaluated for horticultural characterizes. Research conducted while developing this protocol identified cultural practices that reduce anthracnose severity such as the use of nitrate forms of nitrogen fertilizer rather than ammonium forms and drip irrigation instead of overhead irrigation. In vitro and field trials identified commercial and experimental fungicides with efficacy for anthracnose control. These results will be used by strawberry breeders, scientists investigating strawberry diseases, extension agents, and growers developing disease control strategies for strawberry farms. Technical Abstract: Following an epidemic of anthracnose crown rot caused by Colletotrichum fragariae, the United States Department of Agriculture, Agricultural Research Service (USDA-ARS) initiated a breeding program in 1976 to develop anthracnose resistant strawberry cultivars adapted to the southeastern USA. A standardized anthracnose screening was developed and used to evaluate over 160,000 progeny from 448 crosses. These crosses were made at the Fruit Laboratory, Beltsville, MD and the resultant seedlings were screened for anthracnose resistance in the greenhouse at the Small Fruit Research Station, Poplarville, MS. Among the resistant seedlings field-tested in Mississippi, 1515 selections were made based on yield, fruit quality, plant habit, and resistance to leaf scorch, common leaf spot, powdery mildew, and two-spotted spider mites. Four anthracnose resistant-breeding lines and one cultivar have been released from this program. Ninety six elite anthracnose resistant selections are currently maintained. Anthracnose resistant selections from the USDA-ARS breeding program have been used as parents in breeding programs worldwide. Research conducted at Poplarville while developing the anthracnose resistant lines has resulted in a broad range of accomplishments including the first report on strawberry in the USA of the anthracnose fruit rot pathogen, C. acutatum. Studies of the effect of cultural practices on the severity and spread of anthracnose in the field demonstrated that strawberries grown in soils with high nitrogen levels are more susceptible than plants grown in soils with lower nitrogen levels or those amended with calcium nitrate. It was also determined that the use of overhead irrigation and plastic mulch in strawberry fields resulted in more severe anthracnose than when drip irrigation and straw mulch were used. |
