Genetic dissection of iron deficiency chlorosis by QTL analysis in cowpea

Cowpea is an important pulse crop in the world. As with other leguminous crops, cowpea shows severe leaf chlorosis, when grown in calcareous soil. This study aimed to identify quantitative trait loci (QTLs) controlling iron deficiency chlorosis ( qIDC ) using a recombinant inbred line (F 7:8 ) biparental mapping population derived from IDC tolerant parent, IT98K-476-8, and IDC susceptible parent, Golden Eye Cream. Phenotyping the population for IDC was done in calcareous soil at Corpus Christi and Weslaco by visible ranking and at Uvalde in the southern Texas, USA with a chlorophyll meter at four developmental stages. Genotyping-by-sequencing (GBS) was used to generate genotypic data. The QTL analysis was carried out on R/qtl and IciMapping v4.0 software. A total of eight QTLs were identified, including one environment-consistent QTL, one development-consistent QTL, two environment-specific QTLs, and four development-specific QTLs. Of these QTLs, s qIDC10.1 (LOD = 5.50) detected on chromosome 10 has the largest effect on IDC explaining 18.0% of the observed IDC phenotypic variation. From the qIDC10.1 interval, three adjacent putative genes, Iron Regulated1/Ferroportin 1 (IREG1/FPN1), IREG2/FPN2 , and 2-oxoglutarate/Fe(II)-dependent dioxygenase-like ( 2-ODD ), were identified, which may play important roles in IDC of cowpea. The IDC QTLs and putative genes identified herein provide necessary tools and gene resources not only for enhanced IDC tolerance breeding, but also for cloning and characterizing the genes involved in IDC in cowpea and related species.