Effects of heat exposure from late sowing on agronomic traits and the technological quality of hexaploid wheat

Heat stress reduces wheat grain yield and affects quality traits relevant to trading and end use. In this study, 98 landraces and 152 elite hexaploid wheat varieties and breeding lines were trialled at two irrigated field sites in southern NSW to better understand heat stress responses and identify promising genotypes for heat tolerance breeding. Potential heat tolerance was defined using performance in heat-exposed late-sown (LS) plots relative to normal-sown (NS) plots, using a regression approach to calculate response indices uncorrelated with awn emergence time and performance per se in NS. The best individual responders for grain yield included genotypes from both Australia and Mexico. On average, lines selected in CIMMYT's High Temperature Wheat Yield Trials (HTWYT) performed well for yield per se in NS as well as for yield response to LS. CIMMYT lines previously selected for large grains under heat stress conditions performed well for grain size in NS and for LS responses of grain size and test weight. Dough peak resistance and time to peak resistance in a mixograph were increased by LS and these traits were positively correlated with grain protein and the occurrence of the Glu-D1d high molecular weight glutenin locus allele, respectively.