The SSR marker CIR246, which is linked to the B 12 gene that confers resistance to race 18 of Xanthomonas axonopodis pv. malvacearum (Xam), was used to evaluate a series of cotton germplasms that were also tested for their response to inoculation with race 18 of Xam (S-295, Delta Opal, 101-102B, Guazuncho-2, Acala 44, Mebane B1, and Stoneville 2B-S9). The allele associated with resistance was amplified in genotypes that carry the B 12 gene (S-295 and Delta Opal) as well as in those that carry B 2 B 3 (101-102B) and B 9L B 10L (Guazuncho-2), indicating that the molecular marker is able to identify genotypes resistant to the Xam races up to race 18, with resistance genes other than B 12 .