Molecular Markers Associated with Fusarium Wilt Resistance in Common Bean.

Fusarium wilt (FW), a disease of common bean (Phaseolus vulgarus), is caused by the fungus Fusarium oxysporum Schl. Fr. f. sp. phaseoli Kendrick and Snyder (Fop). It is a serious disease in the High Plains, and can cause crop losses up to 50%. Because cultural and chemical control of FW is limited in effectiveness due to long term survival of chlamydospores in the soil, genetic resistance, which is specific to races of the pathogen, is considered the best method to control FW. The objective of this research was to identify molecular markers linked to alleles conferring resistance to races 4 and 5 Fop. A recombinant inbred line population (RIL, n=131) was developed from a cross between the cultivar Sierra and the experimental line LEF-2RB. Based on previous studies, Sierra possesses a single dominant gene that confers resistance only to race 4 Fop, and LEF-2RB possesses an independent dominant gene that confers resistance to both races 4 and 5 Fop.  The RIL population was evaluated using RAPD, SSR, and AFLP molecular markers and for response to inoculation with Fop, rated on a 1 to 9 disease severity scale.  We identified 11 molecular markers located in bean linkage group 11 significantly associated (P < 0.01) with variation for resistance to Fop races 4 and 5; the resistance allele was from LEF-2RB. Two RAPD markers flanked the resistant locus, three and four cM from the locus, respectively. We also identified markers associated with race 4 resistance from the parent Sierra. These markers should enable plant breeders to enhance resistance to FW using marker assisted selection in common bean.