Monday, November 13, 2006

Molecular Markers Linked to White Mold Resistance in Common Bean.

Judd Maxwell1, Mark Brick2, Patrick Byrne3, Howard Schwartz4, and Xueyan Shan4. (1) North Carolina State Univ, 1243 Teakwood Pl, Raleigh, NC 27606, (2) Colorado State Univ, Dept. of Soil & Crop Sciences, Fort Collins, CO 80523-1170, (3) Colordao State Univ, Dept. of Soil & Crop Sciences, CD 1170, Fort Collins, CO 80523, (4) Colorado State Univ, Dept. Bioagricultural Sciences and Pest Management, Fort Collins, CO 80523

White mold, caused by Sclerotinia sclerotiorum (Lib.) de Bary, can cause high yield losses in common bean (Phaseolus vulgaris L.). Most common bean cultivars are susceptible to white mold and resistance is quantitatively inherited. The objective of this study was to identify resistance to white mold found in the Andean common bean line G 122. A recombinant inbred line (RIL) population developed from a cross between G 122 and a susceptible pinto line. A greenhouse tests were used to evaluate reaction to white mold for each line. Two RIL had higher resistance than G 122 based on the average disease severity index (DSI) including, lines 31 and 67 which had DSI of 3.2 and 3.4, respectively, compared to 4.5 for the resistant parent G 122. One hundred twenty four molecular markers were used to map the CSU RIL population based on AFLP, SSR, RAPD and SCAR markers. A significant relationship (P < 0.01) was found between the B7 QTL previously reported to be linked to resistance in our population based on greenhouse tests. Based on composite interval mapping (CIM) strong evidence indicated that four additional QTL influenced physiological resistance to white mold. The QTL were linked with marker loci on linkage groups B1, B2, B8, and B9, respectively. These results provide plant breeders with a better understanding of resistance to white mold and molecular tools to enhance selection for resistance.