Detection of quantitative trait loci for salt tolerance in zombi pea [Vigna vexillata (L.) A. Rich

Abstract

Zombi pea [Vigna vexillata (L.) A. Rich] is an underutilized legume crop, with highly diverse wild species that carry genes conferring resistance to several biotic and abiotic stresses. The objective of this study was to construct a zombi pea genetic linkage map and locate quantitative trait loci related to salt resistance. A zombi pea F2 population (159 individuals) developed from a cross between the salt-resistant wild zombi pea accession JP235908 (var. ovata; female parent) and the salt-susceptible cultivated zombi pea accession TVNu240 (var. macrosperma; male parent) was genotyped with simple sequence repeat (SSR) and restriction site-associated DNA sequencing (RAD-seq) markers. A genetic linkage map with 10 linkage groups (LGs) was constructed based on 379 markers (136 SSR and 243 RAD-seq markers). The map spanned 793.25 cM, with a mean distance between adjacent markers of 2.14 cM. A comparative genome analysis revealed high macro-synteny between zombi pea and mung bean/adzuki bean, although several chromosomal translocations likely occurred in zombi pea. The salt tolerance of the F2:3 population was evaluated at the seedling stage under hydroponic conditions. Inclusive composite interval mapping identified three quantitative trait loci (QTLs) (qSaltol1.1 on LG1, qSaltol2.1 on LG2, and qSaltol6.1 on LG6) related to the salt resistance of the F2 population. The qSaltol1.1, qSaltol2.1, and qSaltol6.1 QTLs explained 13.3%, 7.6%, and 8.1% of the salt-resistance phenotypic variance, respectively. A comparative genome analysis revealed that qSaltol1.1 may correspond to the Saltol1.1 QTL conferring salt tolerance in beach cowpea [Vigna marina (Burm.) Merr.], which is a halophytic species. Moreover, two genes encoding a plasma membrane H+-ATPase and a gene encoding a cation/proton exchanger may contribute to the salt resistance of zombi pea and beach cowpea. These findings may be relevant for the breeding of salt-resistant zombi pea plants.