Quantitative trait loci diversity for salt tolerance at the early growth stage of barley (Hordeum vulgare L.)

Salt tolerance in crops is multigenic in nature and quantitatively inherited, and therefore controlled by minorgenes. To study the diversity of QTLs conferring salt tolerance in barley, four barley mapping populations including L۹۴ × Vada (L × V, ۱۰۳ RILs), Oregon Wolf Barley (OWB) (Dom × Rec, ۹۴ DHs), SusPtrit × Vada (Su × V, ۱۵۲ lines), and SusPtrit × Cebada Capa (Su × CC, ۱۱۳ lines) were tested; L × V and OWB showed unexpected segregation for salt tolerance at an early growth stage and were selected for this study. Two morphological traits (shoot length and total root length) were quantified under different salinity levels (۰, ۲۰۰ and ۳۰۰ mM of NaCl) at an early growth stage. In total, eight QTLs were mapped in OWB and eight QTLs were mapped in L × V under ۲۰۰ and ۳۰۰ mM NaCl; of these, only two QTLs were common to the two populations. In the OWB and L × V populations, two and one QTLs were shared between two traits, respectively. Comparing QTL positions on a consensus map of barley showed that the number and location of the identified salt tolerance QTLs varied depending on the different NaCl concentrations and barley genotypes. Hence, there is a high diversity of QTLs conferring salt tolerance at the early growth stage of barley. In each barley genotype, a set of specific QTLs was responsible for salt tolerance and very few QTLs were common to them.