Identification of QTL Associated with White Mold Resistance in Common Bean

Abstract

White mold, caused by the necrotrophic fungus Sclerotinia sclerotiorum (Lib.) de Bary, is a serious disease of common bean ( Phaseolus vulgaris L.). The use of resistant cultivars is the preferred control strategy, but the approach has been difficult to implement because of quantitative nature of genetic resistance to white mold. The objectives of this study were to identify quantitative trait loci (QTL) associated with resistance to S. sclerotiorum , identify QTL associated with agronomic traits that contribute to white mold avoidance, and locate putative QTL on the integrated bean map. Bulked segregant analysis using multiple trait bulks that included disease severity index (DSI), yield, and days to flower was used to detect QTL associated with field resistance to white mold in a Middle American recombinant inbred line (RIL) population of common bean. QTL that accounted for 9.2 to 14.7% of the phenotypic variation for DSI were located on linkage groups B2, B5, B7, and B8 of the integrated bean map. In addition, QTL were detected for seed size and yield and agronomic traits associated with disease avoidance: days to maturity, days to flower, and lodging. Heritability estimates for DSI were moderate (0.41) and correlations with agronomic traits that included lodging (0.56**), architecture (0.35**), canopy height (−0.33**), and yield (−0.64**) support the importance of these traits in disease avoidance. Data from the current study provides breeders with critical information on which traits and genomic regions to target as part of an overall strategy to enhance resistance to white mold in common bean.