Identification of novel QTLs for salt tolerance in zombi pea (Vigna vexillata)

Soil salinity is a major abiotic stress in agricultural production, as it hampers the growth and development of crop plants. Developing crop cultivars with salinity/salt tolerance is a major goal in many plant breeding programs. This study aimed to identify quantitative trait locus (QTL) that controls salt tolerance in the wild zombi pea (Vigna vexillata) accession "AusTRCF 322105." For QTL analysis, a BC1F2 population resulting from the cross between salt-susceptible TVNu240 and TVNu240 x AusTRCF 322105 was used. A genetic linkage map was constructed for the BC1F2 population, consisting of 15 linkage groups and using 296 SNP markers. The map spanned 2889.9 cM in total length. Plant leaf wilt and plant survival were evaluated by subjecting the BC1F2 population to a hydroponic condition with 250 mM NaCl to assess salt tolerance at the seedling stage. QTL analysis revealed that two QTLs, qSaltol_3.1 and qSaltol_7.1, control both leaf wilt and plant survival. These two QTLs explained 23-27% and 11-15% of the trait variation. Exploration of the physical genome region revealed that qSaltol_3.1 is located near genes encoding methionine sulfoxide reductase and protein L-isoaspartate O-methyltransferase that are involved in oxidative stress resistance. In contrast, qSaltol_7.1 is located near genes encoding 3-ketoacyl-CoA synthase, L-type lectin domain containing receptor kinase VII.1, lipoxygenase 3, CBS domain-containing protein 5, NAC25 protein, and asparagine synthetase (ASNS) that have been found to be associated with salt tolerance. Nonetheless, qSaltol_3.1 and qSaltol_7.1 are novel QTLs identified for salt tolerance in the zombi pea.