Determination of chromosomes that control physiological traits associated with salt tolerance in barley at the seedling stage

Salt stress is one of the most important abiotic stresses, and plays an important role in reducing the yield of crops worldwide. It is now recognized that tolerance to salinity is genetically and physiologically complex and also inherited quantitatively. Barley is a short-season, early maturing, diploid and self pollinating crop, thus it is an ideal model plant for genetic and physiological studies of salinity tolerance. In order to map the genes/QTLs for salinity tolerance in barley, 72 doubled-haploid lines derived from a cross between ‘Steptoe’ and ‘Morex’ were used in an experiment using a randomized complete factorial design with three replications. The phenotypic traits under study included: chlorophyll contents, chlorophyll fluorescence (Fo, Fv, Fv/Fm), proline and carbohydrate rates, relative water content (RWC) and dry and wet weight of plant. Analysis of variance results showed that there were significant differences among the lines and different levels of salinity for all the traits. The strongest correlation was observed between dry and wet weight of plant (r = 0.95**). QTL analysis was performed using the genetic linkage map derived from 327 RFLP molecular markers and QTL cartographer software with the composite interval mapping method. Phenotypic variations that were explained by these QTLs, ranged from 10.64 to 24.20. The highest and lowest phenotypic variances were related to chlorophyll content (Q3cls) and Fv/Fm (Q1fv/fms), respectively. LOD values ranged from 2.77 to 6.33. The highest LOD scores were attained for Fv/Fm on chromosome 2H. Physiological traits associated with salt tolerance in this population were mapped to chromosomes 1H, 2H, 5H and 7H.Key words: Barley, QTL, salinity, stress, tolerance