Molecular Markers Linked to Quantitative Trait Loci for Resistance to Fusarium Wilt Race 6 in Common Bean.

Fusarium wilt (FW) is a serious disease of common bean (Phaseolus vulgaris L.) that causes leaf chlorosis, plugging of the vascular tissue and decrease in crop yield. FW is caused by the fungus Fusarium oxysporum Schlectend. Fr. E. f. sp. phaseoli. Genetic resistance is the preferred approach to limit damage caused by thispathogen because other cultural methods les effective. Genetic sources that confer resistance are known, however molecular markers and genetic maps have not been developed to allow marker assisted selection.  The objectives of this study were to locate and characterize quantitative trait loci (QTL) associated with resistance to race 6 of the pathogen (isolate number Fop 58) in the RIL population Lef-2RB X Sierra. Lef-2RB shows resistance to Fop 58,while Sierra is susceptible. Previous research used SSR, AFLP and RAPD primers to screen 139 recombinant inbred lines (RIL) of the population that had been evaluated for Fop 58 resistance on a scale of 1 (resistant) to 9 (susceptible).  To date, SSR, RAPD and 4 AFLP markers have been screened to seek QTL.  We found two flanking markers surrounding a major QTL from Lef-2RB that provides resistance to Fop 58.  One of the two markers, SSR ATA-32, explained 61.9% of the phenotypic variation and the second marker, RAPD marker OPU-1490 explained 58.9% of the phenotypic variation.  The closeness of the RAPD marker to the QTL makes it a promising candidate to develop a sequence characterized amplifiedregion marker for use in Marker Assisted Selection for resistance to FW.