An SSR marker in the nitrate reductase gene of common bean is tightly linked to a major gene conferring resistance to common bacterial blight

A simple sequence repeat (SSR) marker composed of a tetra nucleotide repeat is tightly linked to a major gene of common bean (Phaseolus vulgaris L.) conferring resistance to common bacterial blight (CBB) incited by Xanthomonas axonopodis pv. phasoli (Xap). This SSR is located in the third intron region of the common bean nitrate reductase (NR) gene, which is mapped to linkage group (LG) H7, corresponding to LG B7 of the bean Core map. Co-segregation analysis between the SSR marker and CBB resistance in a recombinant inbred line (RIL) population demonstrated a tight linkage between the NR gene-specific marker and the major gene for CBB resistance. In total, the marker explained approximately 70% of the phenotypic variation in the population. Because it is co-dominant, this SSR marker should be more efficient for marker-assisted selection (MAS) than dominant/recessive random amplified polymorphic DNA ( RAPD) or sequence characterized amplified region ( SCAR) markers that have been developed, especially for early generation selection.