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<OL> <LI>Collect and characterize Pythium blight causing organisms on snap bean and other hosts from different locations. <LI>Examine fungicide sensitivity of Pythium blight causing organisms in laboratory and field studies. <LI> Screen existing snap bean cultivars and breeding lines for resistance/tolerance to Pythium blight. <LI>Dissemination of results through extension and research channels to ensure that pertinent information is in the hands of snap bean and other susceptible crop producers. </OL> The expect outcome of this project is to devise a reliable system that involves the combination of the researched facets to allow growers to reduce the severity of Pythium blight on snap bean and other susceptible hosts. The elimination of Pythium blight in the short term may not be an obtainable goal, however, if losses can be reduced to acceptable levels through the implementation of an integrated disease management program economic profitability and industry sustainability can be obtained.
Non-Technical Summary: The temperate climates on the East Coast are highly suitable for snap bean (Phaseolus vulgaris L.) production, however, the same conditions that favor snap bean production are also conducive for Pythium blight, which has become one of the most severe diseases of snap beans in the US. Although this disease is well documented, limited information is available concerning which species of Pythium and Phytophthora are most responsible for disease damage. Understanding the etiology of Pythium blight on snap bean and other hosts is necessary to achieve disease control. The first objective of this research is to establish the causal agent(s) of Pythium blight, examining variation in strains collected from different hosts and locations. To date, several isolates were collected on the Eastern Shore of Virginia and attaining additional isolates is necessary to establish the primary causal agent nationwide. Current isolates were identified to species using morphological characterization, and confirmed by molecular techniques. Most isolates were identified as Pythium aphanidermatum using both methods, and variation in virulence on multiple hosts will be determined. The potential variation in sensitivity within this pathogen population to fungicides will be evaluated. Sensitivity has not been reported in isolates from vegetable crops, and will be tested in vitro and in vivo. Preliminary research was conducted to develop field and greenhouse inoculation methods of Pythium blight on snap beans for fungicide sensitivity screenings. This research aims to increase our understanding of the causal agent(s) of Pythium blight and its possible variation in sensitivity to effective fungicides. <P> Approach: OBJECTIVE 1 - Collect and characterize Pythium blight causing organisms on snap bean and other hosts from different locations. Isolate collection - Pythium cottony leak-causing isolates will be collected from Virginia, New Jersey, Georgia and other cooperating states. Isolate identification and characterization - Collected isolates will be classified using morphological and DNA sequencing techniques to determine which species of Pythium they are. Isolates will be tested for host specificity in greenhouse trials to further characterize these isolates. OBJECTIVE 2 - Examine fungicide sensitivity of Pythium blight causing organisms in laboratory and field studies - Collected isolates will be screened for fungicide sensitivity in laboratory studies. Copper hydroxide, mefenoxam, cyazofamid, fluopicolide, azoxystrobin, and propamocarb are some fungicides that will be utilized in this testing. Fungicide field trials will be conducted to assess efficacy of materials in Virginia, Georgia, and New Jersey on snap bean and squash. OBJECTIVE 3 - Screen existing snap bean cultivars and breeding lines for resistance/tolerance to Pythium blight - Commercially available cultivars will be obtained for greenhouse and in-field screening. During the fall of 2009, selected cultivars will be screened initially in greenhouse trials. Cultivars demonstrating resistance/tolerance to Pythium blight will be further evaluated in field trials. These field trials will be conducted in the spring and fall of 2010 and the spring of 2011. OBJECTIVE 4 - Dissemination of results through extension and research channels to ensure that pertinent information is available for vegetable producers - Results from this project will be presented at field days, grower production meetings, scientific meetings, and other pertinent avenues. Results will be incorporated into grower recommendation guides and be distributed in extension publications. Refereed journal articles from this research will also be published.