Submergence stress in rice: Adaptive mechanisms, coping strategies and future research needs

Abstract

Rice is a crop of primary importance in regions, where two-thirds of the world’s starving population reside. Recent climate change projections anticipate spatial shift in precipitation pattern and increase of flooding events that may have negative effects on rice yield and economic returns. Efforts for increasing rice production in areas prone to submergence stress will directly benefit hundreds of millions of people dependent on rice as their staple nfood. This necessitates an objective review of physiological mechanisms and management practices, which could sustain crop productivity under partial or complete submergence. Submergence usually reduces photosynthesis rate that results in quick depletion of the carbohydrate reserve and ultimately the plant dies. Varieties introgressed with SUB1A QTL maintains higher activity of alcohol dehydrogenase and low rate of chlorophyll degradation and thus exhibits better survival under submergence. Prolonged submergence results in a significant reduction in soil redox potential and the heavy influx of flood water promotes runoff, volatilization and deep percolation which leads to loss of sizeable amount of nutrients and ultimately causes nutrient deficiency in soil. Thus, to ensure optimum yield, it is essential to alter the nutrient schedule when plant is subjected to submergence stress. Agronomic management practices like seed priming, higher seed rates, alteration in crop geometry and other improved seeding methods enhance production efficiency by boosting germination, early growth and optimum partitioning of photosynthates to vegetative and reproductive parts. This review critically explores the complex problems faced by rice crop during submergence, physiological mechanisms that helps plant to cope up the submergence stress, as well as available cost-effective management strategies to arrest the yield decline