Drought stress in rice: Morpho-physiological and biochemical responses and breeding approaches for genetic improvement

Abstract

Rice is an important food grain crop for most of the population living in Southeast Asian countries. About half of the rice area across the world is under rainfed conditions, where drought stress is a major constraining factor for its productivity. The occurrence of drought is not stage-specific and can occur at any developmental stage, i.e., seedling, vegetative and reproductive, causing a huge loss in crop establishment and grain yield. Multi-stage drought stress adversely impacts plant growth, seed germination, spikelet fertility, photosynthesis, membrane stability, grain size and grain yield. However, plants acquire enhanced tolerance to lessen the negative impacts of drought stress. Plants that accumulate high proline, starch, glycine betaine and have enhanced activity of antioxidant enzymes like superoxide dismutase (SOD) and catalase (CAT) show better tolerance to drought. The understanding of various morphological, physiological and biochemical responses makes the evaluation and selection of tolerant genotypes easier. Further, molecular and omics-based approaches help in understanding the role of important genes linked to drought stress tolerance. Therefore, the present review attempts to discuss the updates on various responses in rice for drought stress alleviation. Moreover, this review also focuses on recent advances in multi-dimensional approaches for enhancing drought stress tolerance in rice. Future breeding programmes in rice should therefore focus on validating key genes and quantitative trait loci’s (QTLs) identified from diverse genetic backgrounds and integrating conventional breeding with modern molecular and genomic tools. Such integrated approaches will support the development and identification of high yielding and drought-tolerant ricevarieties.