QTL analysis of genetic resistance to white mold (Sclerotinia sclerotiorum) in common bean (Phaseolus vulgaris)

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 varieties is a preferred disease control strategy for white mold but has been a difficult management strategy to implement as no major genes for resistance have been identified in common bean. The objectives of this study were to: (i) to identify AFLP and RAPD markers linked to quantitative trait loci (QTL) associated with resistance to S. sclerotiorum in a Middle American mapping population of common bean; (ii) map the putative QTL to the bean integrated map; (iii) identify QTL associated with important agronomic traits and their relationship with resistance to white mold; (iv) test the potential of marker assisted selection using previously identified markers linked to QTL for resistance to white mold in bean; (v) introgress genetic variability from landrace and wild genotypes into adapted genetic background of cultivated common bean.; The Bunsi/Raven RIL population was evaluated for AFLP and RAPD markers linked to QTL for resistance to white mold in the field and greenhouse. Multi-trait bulking segregant analysis including disease severity, yield and days to flowering was used to detect markers linked to QTL for resistance to white mold. QTL for disease severity index (DSI) using composite interval mapping were detected on linkage groups B2, B5, B7 and B8. The QTL for DSI on B2 and B7 supported results from previous studies, suggesting that QTL for DSI are located in those genomic regions and can be used in marker assisted selection. Important QTL were detected for agronomic traits: days to maturity (R2 = 28.5%) on B2, days to flowering (R2 = 35.7) on B7, lodging (R2 = 29.8) on B7, seed size (R2 = 20.1%) on B2 and (R2 = 25.7%) on B7 and yield (R2 = 9.7%) on B2, and (R2 = 12.7%) on B8, and (R2 = 21.5%) on B7.; Marker assisted selection (MAS) was performed in a Bunsi/Midland recombinant inbred line (RIL) population using previously identified markers linked to QTL for resistance to white mold, in the cultivar Bunsi. The two groups of RILs (selected and control) resulting from MAS were significantly different for DSI (p = 0.03), supporting the potential use of MAS to improve resistance to white mold in common bean. (Abstract shortened by UMI.)...