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Peanut cultivar selection for the development of resistance to Sclerotinia blight

Maas, Andrea Lynn
Scope and Methods of Study: The objectives of these studies were two fold and Included a study to determine inheritance of resistance to Sclerotinia blight in peanut utilizing detached-shoot inoculations, and a field study to evaluate the effects of space planting on disease incidence and severity of Sclerotinia blight in peanut research plots. Diallelic crosses were made utilizing 'Tamspan 90', 'Southwest Runner', 'Okrun' and 'Flavor Runner 458' as parents. 365 F1 plants and 1144 F2 plants were utilized to calculate AULEC values for analysis of inheritance. The four cultivars were also studied in the field utilizing a randomized complete block design with split plots for four seeding rates. Disease incidence and severity were recorded for all plots over two years and analyzed for differences among treatments.
Findings and Conclusions: In the detached shoot study high environmental variances produced inconclusive measures of genotype. Current results suggest complex mechanisms of inheritance which may include quantitative, dominance, epistasis, and cytoplasmic effects. In the field study plots evaluated on a presence/absence for date of initial disease symptoms indicated that disease would be present in susceptible plots within two weeks of disease initiation. Disease incidence presented clear trends of increasing with level of susceptability and increased plant spacing at a significance level of p=0.05. Disease severity was reduced overall in the two resistant cultivars but was not significant at p=0.05 and thus not sufficient to differentiate susceptible from resistant plants. Use of a combination of disease onset and final disease incidence may provide an efficient selection tool for resistance to Sclerotinia minor.