Molecular Basis of Salt Tolerance in Wheat and Other Crop Plants

Abstract

Among abiotic stresses, salinity has become a major problem adversely affecting the growth of crop plants grown under saline conditions. In India, an area of about 5.5 mha is already under salinity and 3.6 mha under sodicity problem, and still larger area is coming under potential salinity problem due to injudicious use of water under canal irrigation system. The plant growth in saline conditions is inhibited mainly by the toxic effect of increased sodium accumulation and nonavailability of water. Thus, salt stress is a major agricultural issue that demands an immediate attention. Various mechanisms to avoid salt accumulation inside cells of root and leaf include sodium exclusion, its sequestration in vacuoles, production of compatible solute, and acceleration of reactive oxygen species scavenging systems. Understanding these mechanisms at physiological and molecular levels is needed to identify new genetic sources of salt tolerance and improve the selection process in breeding. More recently, in addition to the conventional mechanisms, several genomic approaches are being used in improving salt tolerance in plants. A significant progress has been made on identification of genes for salt tolerance in wheat, and the studies related to gene expression are underway. This review describes the various tolerance mechanisms adopted by crop plants, especially wheat, under saline conditions.