Molecular markers selection for disease resistance and other traits in intraspecific bean species crosses

Common bacterial blight and bean rust, incited by Xanthomonas campestris pv. phaseoli (Xcp) and Uromyces appendiculatus, respectively, are serious diseases of common bean (Phaseolus vulgaris L.). Seed weight is an important trait in common bean. RAPD markers linked to major dominant genes for resistance to Xcp were identified using bulked segregant analysis (BSA) in an F$\sb2$ population from the tepary bean cross CIAT-640005 x Nebr.#4B. Twelve markers were mapped in a coupling phase linkage with three genes for resistance to Xcp. The linkage group spanned a distance of 19.2 cM. RAPD markers linked to major dominant genes for specific rust resistance and indeterminate growth habit were detected using BSA in an F$\sb2$ population from the common bean cross PC-50 x Chichara. Six markers were mapped in a coupling phase linkage with the gene far resistance to the D82VC-74fh rust pathotype. Twenty-eight markers were mapped in a coupling phase linkage with the gene (Fin) for indeterminate growth habit. The number of genes controlling resistance, heritability of resistance, and correlation of leaf and pod reactions to Xcp were estimated in a recombinant inbred (RI) population derived from the common bean backcross BC$\sb2$F$\sb6$PC-50 x XAN-159. One to two genes controlled leaf and pod resistance to Xcp. Low to intermediate narrow sense heritabilities for leaf and pod reactions to two Xcp strains were estimated. Low to intermediate Pearson correlations were observed between leaf and pod reactions to Xcp. RAPD markers associated with QTL affecting leaf and pod resistance to Xcp were detected in the above cross. Four markers were associated with the resistance to Xcp. One to two QTLs explained from 20 to 51% of the total phenotypic variation for leaf and pod reactions to five Xcp strains. RAPD markers associated with QTL affecting bean seed weight, seed length, seed height, and pod length were detected in an RI population from the cross PC-50 x XAN-159. One to three QTLs affecting seed weight explained 17% to 41% of the phenotypic variation. Two to three QTLs for seed length explained 23% to 45% of the phenotypic variation. One to four QTLs associated with seed height explained 17% to 39% of the phenotypic variation. One to two QTLs affecting pod length explained 19% and 24% of the phenotypic variation