WHEAT CULTIVARS VARY WIDELY IN THEIR RESPONSES OF GRAIN-YIELD AND QUALITY TO SHORT PERIODS OF POSTANTHESIS HEAT-STRESS

Short periods of high temperature (> 35 degrees C) are common during the post-anthesis period in Australian wheat crops and have recently been shown to significantly reduce grain yield and quality. In view of this, 75 cultivars of wheat were screened for tolerance to 3 days of high temperature (max. 40 degrees C). Detailed results for grain yield and quality are presented for Five wheat cultivars in order to illustrate the wide range of responses to short periods of high temperature, Individual kernel mass decreased by up to 23%, depending on variety, and the gliadin:glutenin ratio altered in the range -9 to +18% in response to high temperature treatment, also depending on variety. Noodle swelling power was significantly affected by heat in two cultivars, but there was no significant change due to heat in the apparent amylose content in any variety. The marked response of several yield and quality components to a heat treatment lasting only ca 5% of the grain-filling period suggests that starch and protein synthesis do not immediately and/or fully recover from short, severe heat stress. In addition, we conclude that wheat shows considerable genetic variability in tolerance to short periods of high temperature for both grain yield and quality.