Identification of RAPD Markers Linked to Major Genes for Common Bacterial Blight (CBB) Resistance Using Bulked Segregant Analysis in a Tepary Bean Cross

Abstract

Common bacterial blight (CBB), incited by Xanthomonas campestris pv. phaseoli (Xcp), an important disease in common bean (Phaseolus vulgaris L.) Tepary bean (P. acutifolius A. Gray) is of interest to bean breeders because of resistance to CBB. Our objective was to identify RAPD markers linked to major genes for CBB resistance using bulked segregant analysis in an F2 population from a tepary bean cross CIAT640005 (R) X Nebr#4B (S). A total of 57 RAPD primers (602 RAPD primers screened) showed polymorphisms between bulked DNA derived from R and S CBB plants. All markers showed coupling linkage with CBB resistance. A good fit to a 3:1 ratio of bands for presence and absence using 11 RAPD primers was observed in 77 F2 plants. Markers of U-15 and L-7 primers were 2.4 cM distant from the gene for resistance to Xcp strain LB-2. RAPD markers of U-10, U-20, S-12, Y-4, F-13, P-6, Q-1, and Q-ll primers were 2.4 cM distant from the gene for resistance to Xcp strain SC-4A. RAPD markers of IJ-15 and L-7 primers were 8.4 cM distant from the gene for resistance to Xcp strain EKl l. The tepary RAPD linkage group includes three molecular markers and three genes for resistance to Xcp strains EK-l l, LB-2, and SC-4A and spans a length of 19.2 cM. This data supports the presence of Xcp races.