HIGH-TEMPERATURE EFFECTS ON RICE GROWTH, YIELD, AND GRAIN QUALITY

Rice (Oryza sativa L.) is a globally important cereal plant, and as a primary source of food it accounts for 35-75% of the calorie intake of more than 3 billion humans. With the likely growth of world's population toward 10 billion by 2050, the demand for rice will grow faster than for other crops. There are already many challenges to achieving higher productivity of rice. In the future, the new challenges will include climate change and its consequences. The expected climate change includes the rise in the global average surface air temperature. At the end of the twenty-first century, the increases in surface air temperature. At the end of the twenty-first century, the increases in surface air temperature will probably be around 1.4-5.8 degrees C, relative to the temperatures of 1980-1999, and with an increase in variability around this mean. Most of the rice is currently cultivated in regions where temperatures are above the optimal for growth (28/22 degrees C). Any further increase in mean temperature or episodes of high temperatures during sensitive stages may reduce rice yields drastically. In tropical environments, high temperature is already one of the major environmental stresses limiting rice productivity, with relatively higher temperatures causing reductions in grain weight and quality. Developing high-temperature stress-tolerant rice cultivars has become a proposed alternative, but requires a thorough understanding of genetics, biochemical, and physiological processes for identifying and selecting traits, and enhancing tolerance mechanisms in rice cultivars. The effects of high-temperature stress on the continuum of soil-rice plant-atmosphere for different ecologies (with or without submerged conditions) also need detailed investigations. Most agronomic interventions for the management of high-temperature stress aim at early sowing of rice cultivars or selection of early maturing cultivars to avoid high temperatures during grain filling. But these measures may not be adequate as high-temperature stress events are becoming more frequent and severe in the future climate. In this review, the effects of high-temperature stress on rice growth, yield, and quality characters, including various morphological, physiological, and biochemical mechanisms along with the possible use of conventional and molecular breeding methods, and crop growth simulation models and techniques are discussed. The mitigation and adaptation strategies for dealing with high-temperature stress in rice are highlighted. We conclude that there are considerable risks for rice production, stemming from high-temperature stress but benefits from the mitigation or adaptation options through progress in rice research may sustain the production systems of rice in the future warmer world.