Engineering Rice for Abiotic Stress Tolerance: A Review

Rice (Oryza sativa L.) is widely grown as a major staple food crop providing calories for about half of the world's human population and is grown on 160 million hectares worldwide. It is being cultivated in India and China for several thousands of years. A significant yield loss in this crop is due to various biotic and abiotic stresses including insect pests, diseases, drought, salinity, adverse temperature and submergence. Development of abiotic stress tolerant rice genotypes with high grain yield is the major objective now in rice breeding and genomic research. Despite many concerted efforts all over the world, conventional breeding approaches are resulting in slow progress in developing abiotic stress tolerant rice genotypes. One of the approaches to rectify this is to introduce genes of interest that confer tolerance to abiotic stress via genetic engineering methods. Besides, with the availability of high quality rice genome sequence (IRGSP, 2005), there has been rapid accumulation of functional genomic resources including many known cloned and characterized genes particularly for abiotic stress tolerance, genes/full-length cDNA from global expression profiles and resequences of the rice genotypes. The identified genes are successfully transferred into rice to produce transgenics with promising traits. Transgenics are now being evaluated under field conditions in different countries. The objective of this review is to provide an overview of recent developments on the production of various transgenic lines in rice that are highly promising for abiotic stress tolerance.