Recent advances in molecular breeding of drought tolerance in rice (<i style="">Oryza sativa </i>L.)

Abstract

Rice is an ideal plant species for genomic studies for its relative small genome size (~430 Mb), diploid origin (2x=24) and close relationship with other important crops. Rice has been grown under diverse ecological conditions and gets exposed to different environmental stresses like drought, salinity, cold, etc. Drought is generally avoided in irrigated rice production system but it is more prone to 63.5 mha of rainfed rice grown annually in different parts of world. Severe osmotic stress causes detrimental changes in cellular components. Yet in response to various environmental stresses, plants have developed different physiological and biochemical strategies to adapt stress conditions, such as, stress associated changes in metabolites and amino acids (proline), amines (glycin-betaine and polyamines), and variety of sugar and sugar alcohols (manitol and trehalose). There is also activation of cascade of molecular networks involved in stress perception, signal transduction and the expression of specific stress related genes. To understand these genetically complex mechanisms of abiotic stress tolerance, an integrated approach of molecular breeding, classical physiology and conventional breeding is necessary, and the present review is an effort to deal these issues.