Physiological traits for evaluating heat-tolerance of Australian spring wheat cultivars at elevated CO2

High temperatures and increasing CO2 concentrations are a major threat to global wheat (Triticum aestivum L.) production, demanding the development of heat-tolerant wheat cultivars. Plant physiological traits are potential surrogates for evaluating genetic variation for crop stress tolerance. This research evaluated 23 Australian wheat cultivars and two breeding lines for heat-tolerance by characterising the associated physiological traits. The interactive effects of heat-stress and elevated CO2 were studied under controlled greenhouse conditions and delayed sowing in the field with exposure to higher temperature. Physiological changes, pollen viability and grain yield were assessed. A significant correlation was observed between physiological and agronomical traits under high temperature at 35 degrees C and elevated CO2 at 800 mu l L-1, providing evidence of adaptation to high temperatures in some genotypes. Variation in stomatal conductance, transpiration rate, canopy temperature, leaf chlorophyll and photosynthesis were associated with maintenance of pollen viability and grain yield at high temperatures. Of the genotypes assessed, seven were classified as heat tolerant at both ambient and elevated CO2 and nine were heat susceptible while the remainder showed a variable response to CO2 at high temperatures. Field data confirmed the heat responses of the most heat-tolerant and susceptible genotypes. The heat tolerant genotypes identified are candidates for further breeding and selection to improve adaptation to a changing climate.

Automated summary

High temperatures and increasing CO2 concentrations pose a major threat to global wheat production. This research evaluated Australian wheat cultivars for heat tolerance and identified physiological traits associated with adaptation to high temperatures. The findings provide valuable candidates for breeding and selecting wheat cultivars that can better adapt to changing climate conditions.