High-resolution genetic and physical mapping of the region containing the Bs2 resistance gene of pepper

The Bs2 resistance gene of pepper confers resistance against the bacterial pathogen Xanthomonas campestris pv. vesicatoria. As a first step toward iso lation of the Bs2 gene, molecular markers tightly linked to the gene were i dentified by randomly amplified polymorphic DNA (RAPD) and amplified fragme nt length polymorphism (AFLP) analysis of near-isogenic lines. Markers flan king the locus were identified and a high-resolution linkage map of the reg ion was developed. One AFLP marker, A2, was found to cosegregate with the l ocus, while two others, F1 and B3, flank the locus and are within 0.6 cM. P hysical mapping of the A2 and F1 markers indicates that these markers may b e within 150 kb of each other. Together, these results indicate that the Bs 2 region may be cloned either by chromosome walker or landing. The linked m arkers were also used to characterize gamma-irradiation-induced mutants at the Bs2 locus.