Salt Tolerance Mechanisms and Approaches: Future Scope of Halotolerant Genes and Rice Landraces

All rice plant developmental stages are severely affected by soil salinity. Salinity-induced ionic and osmotic stresses affect stomata closure and gaseous exchange, and reduce transpiration and the rate of carbon assimilation, and hence decrease plant yield. Understanding the response of rice plants toward salinity stress at the genetic level and developing salt-tolerant varieties are the vital mandates for its effective management. This review described the present status of salt-tolerance achieved in rice by various mechanisms including the ion homeostasis (Na+/H+, OsNHX antiporters), compatible organic solutes (glycine betaine and proline), antioxidative genes (OsECS, OsVTE1, OsAPX and OsMSRA4.1), salt responsive regulatory elements (transcription factors, cis-acting elements and miRNAs) and genes ecoding protein kinases (MAPKs, SAPKs and STRKs). Further, the future perspective of developing salt-tolerant varieties lies in exploring halotolerant gene homologs from rice varieties, especially the landraces. Genetic diversity among rice landraces can serve as a valuable resource for future studies toward variety improvement through breeding and genome editing. Further, identification, multiplication, preservation and utilization of biodiversity among landraces are the urgent buffers to be saved as a heritage for future generations to come.