Quantitative Trait Loci Linked to White Mold Resistance in Common Bean

Abstract

White mold disease (WM) of common bean (Phaseolus vulgaris L.), caused by Sclerotinia sclerotiorum (Lib.) de Bary, reduces crop yield and quality throughout the United States. The development of cultivars with resistance to WM would be facilitated by the identification and use of molecular markers linked to resistance genes. The objectives of this research were (i) to characterize WM reaction in a recombinant inbred line (RIL) population derived from a cross between resistant and susceptible germplasm, (ii) to validate the effect of a previously reported quantitative trait locus (QTL) for WM resistance, and (iii) to locate additional QTL associated with WM resistance. A RIL population that consisted of 94 lines was derived from a cross between G122 (resistant) and CO72548 (susceptible). The population was evaluated for WM reaction in three greenhouse tests and one field environment, and for molecular markers throughout the genome. Two RIL were identified with higher resistance levels (P < 0.05) than the resistant parent G122. A previously reported QTL on linkage group B7 was significant (P < 0.01) in single‐factor analysis of variance, but not with composite interval mapping. Five QTL for resistance to WM were found (likelihood odds ratio [LOD] > 2.7) on linkage groups B1, B2b, B8, and B9. The QTL were contributed from both parents and together accounted for 48% of the phenotypic variation (R2). For field resistance, one QTL (R2 = 12%) on linkage group B8 was detected. These results confirm polygenic resistance to WM in common bean.