Detection and Mapping of a Major Locus for Fusarium Wilt Resistance in Common Bean

Fusarium oxysporum Schlectend. Fr. f. sp. phaseoli J.B. Kendrick and W.C. Snyder (FOP) is a vascular pathogen that causes Fusarium wilt in common bean (Phaseolus vulgaris L.). This disease is an increasing problem in the western U.S., and exploitation of genetic resistance is considered the most feasible control method. The objective of this study was to detect quantitative trait loci (QTL) for Fusarium wilt resistance in a population derived from an interracial cross between FOP‐susceptible Belneb RR‐1 (race Durango) × FOP‐resistant A55 (race Mesoamerica). Seventy‐six F6‐derived recombinant inbred lines (RILs) were screened for disease severity in greenhouse inoculations and rated on a scale of 1 (resistant) to 9 (susceptible). The phenotypic data were compared to existing random amplified polymorphic DNA (RAPD) marker data using single‐factor analysis of variance. Marker U20.750 on linkage group (LG) 10 accounted for 63.5% of the phenotypic variance for this trait. Lines exhibiting the A55 banding pattern at this locus had disease severity scores that averaged 3.6 points lower than lines with the Belneb RR‐1 pattern. Two additional markers, AD4.450 on LG 3 and K10.700 on LG 11, were significant (P < 0.01) in single‐factor analysis of variance, but only marker U20.750 on LG 10 remained significant when composite interval mapping (CIM) was conducted. The tight linkage between the putative QTL and U20.750, as indicated by CIM, makes this marker a promising candidate for conversion to a sequence‐characterized amplified region (SCAR) for use in marker‐assisted selection in Fusarium wilt resistant common bean cultivar development.