Identification of salt-tolerant barley varieties by a consolidated physiological and molecular approach

Soil salinity is a significant international environmental problem and severely affects the yield of cereal crops due to numerous effects on plant-water relations, ion homeostasis and salt toxicity. This work assessed the salt tolerance levels of 16 barley varieties by key physiological and molecular tests. Seedlings were exposed to acute salinity stress and their physiological responses including relative water content, levels of the stress hormone abscisic acid (ABA) and Na+/K+ ratio were compared. A significant variation was noted amongst the varieties, with Calmariout, Hindmarsh and Mundah identified as tolerant varieties and Franklin as the most sensitive variety. Further, the differential expression of key genes in the ABA-regulated stress response pathway, i.e., pyrabactin resistance (PYR)/PYR-Like (PYL)/regulatory components of ABA receptors (RCAR), protein phosphatase 2C (PP2C), sucrose non-fermenting 1-related kinase (SnRK2) and specific ABC transporters, was analysed by quantitative real-time PCR of leaf RNA. The PP2CA and ABC transporters were up-regulated while the PYR/PYL/RCARs and SnRK2s were down-regulated under salt stress. Importantly, tolerance ranking by gene expression closely correlated that by physiological indices. Thus expression analysis of the ABA pathway may be used for rapid identification of potentially salt-tolerant barley varieties before undertaking physiological studies. The outcomes are relevant for varietal selection and comparing the alleles for genetics of tolerance.