Confirmation of QTL associated with common bacterial blight resistance in four different genetic backgrounds in common bean

Common bacterial blight (CBB), incited by the bacterial pathogen Xanthomona s campestris pv. phaseoli (Smith) Dye (Xcp) is a major problem in bean (Pha seolus vulgaris L.) producing areas worldwide. Using 128 recombinant inbred (RI) lines derived from the common bean cross BAC 6 x HT 7719, RAPD marker locus-QTL associations were previously described for resistance to two Xcp , strains, EK-11 and Epif-IV. The objective of this research was to test th ese candidate marker locus-QTL associations in three previously untested ge netic populations. In addition, RAPD marker locus-QTL associations were als o investigated for resistance to a third Xcp strain, DR-7, in the first tri foliolate leaves in the original BAC 6 x HT 7719 population. The three geno mic regions most significantly associated with CBB resistance in the origin al BAC 6 x HT 7719 population were significantly associated with CBB resist ance in at least two of the three additional populations. The unmapped mark er, BC409.1250, was significantly associated with CBB resistance in all fou r populations and all three Xcp strains, suggesting that tills marker might be tightly linked to genes for CBD resistance. The RAPD marker BC409.1250 was converted into a marker that is a robust and reliable PCR-based marker. Since similar genomic regions were found for resistance to three different Xcp strains, these QTL may be useful for breeding cultivars with a broad r ange of resistance.