Quantitative Trait Loci mapping of agronomic traits in a cowpea (Vigna unguiculata L.) bi-parental cross

Abstract

Although Cowpea is an important food legume with multiple benefits in sub-Saharan Africa (SSA) its productivity on farmers’ fields is very low due to biotic and abiotic stresses, and by the paucity of useful trait-linked genetic markers or QTLs for agronomic traits. Hence, the objective of this study was to construct genetic linkages map of cowpea and identify regions of the genome associated with agronomic traits of cowpea in the F2 population (200 progenies) developed from a cross between a cowpea line (TVu2185) and a yard-long bean line (TVu6643). Diversity Array Technology genotyping platform was used for SNP genotyping the DNA samples. The linkage map and QTL analysis were performed using Join Map® 4.1, and MapQTL® 6 QTL mapping programs, respectively. The linkage map spanned 689 cM of the cowpea genome. Major and minor QTLs (15 in total) were detected for the agronomic traits studied on 6 of the 11 LGs in cowpea. The major seed traits related QTLs were present on LG8 along with that for pod length. The highest phenotypic variance explained (PVE) by individual QTL was 31.2% for seed length followed by 21.1% for seed number per pod on LG8. The phenotypic variance explained by all QTLs per trait ranged from 10.2% for SPW to 48% for SL. The QTLs with large effect detected for pod length and seed traits indicates that the QTLs are potential candidates for marker development and marker assisted selection in cowpea.