Phenotypic, physiologic, and heat-induced gene expression analysis in diverse spring wheat genotypes under heat stress

J. HE 1, A. ABBAS 1, W. JIANG 1, Z. CHEN 1,2

1 School of Science, Western Sydney University, Richmond NSW 2753, Australia

2 Hawkesbury Institute for the Environment, Western Sydney University, Richmond NSW 2753, Australia

Climate change is increasing the frequency of extreme weathers such as heat waves, limiting wheat photosynthesis activities and carbohydrates accumulation in grains. Molecular studies have revealed that wheat heat tolerance is under polygenetic control; many of these genes encode proteins in heat shock signalling and responsive pathways or are associated with staygreen and spikelet fertility traits. In this work, four popular Australian commercial spring wheat genotypes (Catapult, Coota, Beckom, Sunmaster) with diverse maturity characteristics were exposed to two-days heat stress (35°C) at their early anthesis stage in the glasshouse, with control at an optimal growth temperature of 20°C. As a mid-maturing cultivar, Beckom showed remarkable heat-tolerant capacities, boosting the expression of several heat-tolerant proteins including heat shock factors, heat shock proteins, and staygreen gene comparing to the control. In contrast, Catapult and Coota are slow maturing varieties and are sensitive to heat stress, presenting inhibited photosynthesis rate, stomatal conductance and maximal carboxylation rate. Sunmaster is early-maturing and showed moderate heat tolerance with good logging tolerance. The reverse-transcription quantitative PCR also showed distinct differences in the expression of protein synthesis elongation factor, RuBiSco Activase, pheide a oxidase, and chlorophyllide a oxygenase across the four varieties.