Monday, November 5, 2007 - 11:35 AM
45-6
Climate Change and Rice: Implications for Crop Adaptation.
Motohiko Kondo, National Agriculture and Food Research Orgnization (NARO), National Institute of Crop Science (NICS), Kannnondai, Tsukuba, Ibaraki, Japan and Shaobing Peng, International Rice Research Institute, CSWSD IRRI, DAPO Box 7777, Metro Manila, PHILIPPINES.
In the history of rice research, the efforts to alleviate low temperature damages have made tremendous achievements to expand rice areas and stabilize yield. Coping with rising temperature and fluctuant climatic conditions is a new challenge for developing adaptive genotype and management. High temperature stress appears in decline of spikelet number, spikelet fertility, reduced grain weight, grain quality, and also through increased water demand and enhanced biotic stresses. Apparent optimum temperature for finial grain yield is lower for ripening stages than for the stages before heading, indicating that high temperature is most critical during grain filling. High temperature above optimum before heading stage reduces yield by shortening vegetative phase, decreasing productive tiller percentage, and lowering spikelet number per panicle. The high temperature during ripening induces chalky appearance, small grain size with ditch on surface, and fissured grain. The causes of chalkiness and small grain are hypothesized to be source limitation, disorder of sink ability or both. It is likely that the supply of substrate for starch synthesis to endosperm becomes limiting with accelerated ripening processes and enhanced respiration. High temperature during anthesis time in a day is most detrimental to spikelet fertility. Several strategies are proposed for varietal improvement in heat tolerance and avoidance during flowering such as theca morphologies which facilitate theca dehiscence and early-morning flowering characters. Factors affecting panicle temperature, such as synergetic effect of high air temperature and elevated CO2 and genotypes, are also to be focused High temperature stresses are magnified with increased transpirational demand, low radiation, and high night temperature. Physiological understanding is essential for the combined tolerance to low radiation and high temperature, especially night temperature. Agronomic practices that cope with expected climate change include the escape of flowering and grain filling from high temperature with optimum planting date, adjusting N management, and soil management for enhancing root functions.