Genetic Enhancement for Salt Tolerance in Rice

Rice is the major and dominant cereal food crop in the world. Salinity stress is the second most abiotic stress next to drought, limiting rice yield. Approximately 953 Mha area of the world is affected by salinity. Genetic improvement of salt tolerance is an efficient approach to achieving yield gain in salt-affected areas. Although high-yielding salt-tolerant rice varieties are developed, it is difficult to generate tailor-made adapted varieties through traditional breeding. Hence various crop improvement approaches are followed, including marker-assisted selection and transgenic technology apart from classical breeding. Numerous QTLs were identified through the molecular marker approach, and specifically, Saltol QTL was introgressed into elite lines through marker-assisted back cross-breeding, and improved salt-tolerant varieties were bred. Genetic engineering tools are also amply employed whereby the genes underlying various biochemical/physiological processes such as ion and osmotic homeostasis, antioxidation, signaling, and transcription-associated with increased tolerance were characterized, validated, and used to develop salt-tolerant lines of rice. Yet, a clear relationship between expected gains in salt tolerance in vitro has often not been observed in the field in terms of grain yield. Hence, an integrated approach involving molecular breeding and conventional breeding would certainly pave the way to enhance salt tolerance in rice. 

Keywords: Rice, Salinity, Alkalinity, Screening techniques, Salt tolerance, Mechanisms of tolerance, Breeding, QTLs, Marker-assisted selection, Transgenics.