Genetic Associations Underpinning the Metabolite-Mediated Salt Stress Tolerance in Barley

Salinity stress is one of the abiotic factors that greatly affect agriculture by limiting plant growth and yield worldwide. A set of 138 barley accessions from different geographical regions was characterized with the aim to identify metabolite, biochemical, and morphological phenotypes under salinity stress. Salt stress resulted in significant increases in the phytochemicals, including the contents of total phenolic (TPC), total flavonoid (TFC), proline (ProC), and total antioxidant capacity (TAC) except soluble protein (SP). Positive relationships between proline content and the secondary metabolites or antioxidants, including total phenolics and flavonoids, were detected among barley accessions, indicating a critical adaptive strategy against free radicals under salt stress. Genome-wide association study (GWAS) revealed 122 significant quantitative trait nucleotides (QTNs) associated with the measured traits which resulted in the identification of 203 potential candidate genes. Interestingly, the QTN G:A was located inside the candidate gene HORVU.MOREX.r3.3HG0291720 at position 501,703,401 on chromosome 3H. This gene encodes Ca-binding protein and contributes to the signalling pathway that in turn triggers the expression of salt-stress responsive genes. The identified QTNs/ candidate genes provide information useful for the genetic improvement of barley genotypes under salt stress.