IDEOTYPE DESIGN FOR HIGH GRAIN YIELD POTENTIAL ON HEAT STRESS WHEAT

A wheat ideotype is represented by a set of cultivar parameters in a model, which could be optimized for best wheat performance under projected heat-tolerant conditions. Globally, heat stress significantly limits the yield. So, a major challenge of the 21st century is to achieve food supply security under a changing climate androughly a doubling in food demand by 2050. Global warming became a serious threat to crop productivity as heat stress sig nificantly reduced grain yield. Although the different traits related to high grain yield have beenidentified, the combination of traits that optimize high grain yield has not been established. The later sown experiments were exposed to higher temperatures at the critical reproductive and grain-filling stages of development. The influence of high temperatures was highest during anthesis, and with every 1% increase in average maximum temperature over the optimum of 25 degrees Celsius, grain yield was lowered by 4% to 7%. High temperature reduced yield, plant height, grain weight and days to anthesis and maturity, and increased the percentage of screenings and grain protein content. Genotypes that produced higher yield under heat stress had shorter days to flowering and maturity, higher NDVI during grain filling, greater chlorophyll content at the milk stage of grain fill, taller plants, greater grain weight and number, and lower screenings compared with the benchmark cultivar Sun top (main factors contributing to yield increase/parameters).