515 Mapping of Molecular Markers and Seedcoat Pattern Associated with QTL Affecting White Mold Resistance in Common Bean

in HortScience
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  • 1 University of Nebraska, Lincoln, NE 68583
  • | 2 University of Wisconsin, Madison, WI 53706

White mold, incited by Sclerotinia sclerotiorum (Ss), is an important disease of common bean (Phaseolus vulgaris). Our objective was to identify RAPD markers and seedcoat pattern associated with QTL affecting resistance to Ss isolates 152 and 279 in a molecular marker-based linkage map previously constructed using a recombinant inbred (RI) population from the common bean cross `PC-50' (resistant to Ss) x XAN-159 (susceptible to Ss). White mold reactions were derived from a greenhouse straw test. Continuous distributions for the reactions to Ss isolates 152 and 279 were observed for RI lines, indicating quantitative inheritance. An intermediate (+0.67) Pearson correlation was observed between the reactions to Ss isolates 152 and 279. Low (0.24 and 0.23) narrow-sense heritabilities were found for the reactions to Ss isolates 152 and 279. Three QTL affecting resistance to Ss isolate 152 explained 33% of the phenotypic variation. Four QTL affecting resistance to Ss isolate 279 explained 54% of the phenotypic variation. The seedcoat pattern marker (C) on linkage group I was most consistently associated with resistance to Ss isolates 152 and 279, and explained 10% and 24% of the phenotypic variation for the traits, respectively. This is the first report on detection of QTL for white mold resistance in common bean. The RAPD markers and seedcoat pattern could be useful in breeding for white mold resistance.

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