Genetic linkage map and mapping of the locus of biological nitrogen fixation inefficiency in cowpea

ABSTRACT. The objectives of the present study were to construct a cowpea genetic map using the F2 population resulting from the cross IC-1 x BRS Marataoã, based on single nucleotide polymorphism (SNP) markers, and to map the cpi gene, with additional reference to introgression with the consensus map of species, aiming to identify markers for assisted selection to develop more efficient cultivars for BNF. The parents and 89 F2 plants were genotyped with 51,128 SNP markers, of which 910 polymorphic markers were used to construct the map. The results revealed 11 linkage groups, with an average of 82 markers per chromosome and average distance of 1.26 cM between markers. Recombination analysis of the SNPs indicated that markers 2_12850 and 2_00188, located in linkage group 11, flanked the cpi gene at a distance of 6.7 cM and 5.64 cM, respectively. The introgression of linkage group 11 with the cowpea reference map revealed short distances (from zero to 0.6 cM) for these markers, indicating a strong association with the cpi gene. The constructed map and cpi mapping provide basic information that can assist the genetic breeding of more efficient cowpea plants for BNF by marker-assisted selection.