Molecular mapping of disease resistance genes for halo blight, common bacterial blight, and bean common mosaic virus in a segregating population of common bean

Diseases of beans (Phaseolus vulgaris L.) are primary constraints affecting bean production. Information on tagging and mapping of genes for disease r esistance is expected to be useful to breeders. The objectives of this stud y were to develop a random amplified polymorphic DNA (RAPD) marker linkage map using 78 F9 recombinant inbred (RI) lines derived from a Middle-America n common bean cross Great Northern Belneb RR-1 [resistant to common bacteri al blight (CBB) and halo blight (HB)] x black A 55 [dominant I gene resista nce to bean common mosaic potyvirus] and to map genes or QTL (quantitative trait loci) for resistance to CBB, HB, BCMV (bean common mosaic virus), and BCMNV (bean common mosaic necrosis virus) diseases, The RI lines were eval uated for resistance to leaf and pod reactions to Xanthomonas campestris pv . phaseoli (Xcp) (Smith Dye) strain EK-11, leaf reactions to two Pserrdomon as syringae pv. phaseolicola (Psp) (Burkholder) Young et al. (1978) strains HB16 and 83-Sc2A, and BCMV strain US-5 and BCMNV strain NL-3. The linkage map spanned 755 cM, including 90 markers consisting of 87 RAPD markers, one sequence characterized amplified region (SCAR), the I gene, and a gene for hypersensitive resistance to HB 83-Sc2A. These were grouped into 11 linkag e groups (LG) corresponding to the 11 linkage groups in the common bean int egrated genetic map. A major gene and QTL for leaf resistance to RE were ma pped for the first time, Three QTL for leaf reactions to HB16 were found on linkage groups 3, 5, and 10. Four regions on linkage groups 2, 4, 5, and 9 , were significantly associated with leaf reactions to HB strain 83-Sc2A. T he gene controlling the hypersensitive reaction to HE 83-Sc2A mapped to the same region as the QTL an LG 4, The I locus for resistance to BCMV and BCM NV was mapped to LG 2 at about 1.4 cM from RAPD marker A10.1750. Five and f our markers were significantly associated with QTL for resistance to CBB in leaves and pods, respectively, with four of them associated with resistanc e in both plant organs. A marker locus was discovered on LG 10, W10.550, wh ich could account for 44% and 41% of the phenotypic variation for CBB resis tance in leaves and pads, respectively. QTL for resistance in pod to CBB,le af resistance to HB, and the I gene were linked on LG 2.