A phenotyping strategy for evaluating the high-temperature tolerance of wheat

Wheat yield is limited by high-temperature and likely to become more variable with climate change. However, while much has been published on wheat responses to high temperature, the phenotyping techniques used often lack relevance to farming conditions or rely too heavily on a single screening strategy. For this reason, a three-tiered screening approach was developed and validated over a three-year period to screen large numbers of materials, primarily in the field. The first tier used different times of sowing to evaluate large numbers of genotypes in yield plots in the field using irrigation to limit the effects of drought stress. Those genotypes with exceptional performance under late sowing were then screened using field-based heat chambers placed on optimally sown plots at anthesis to induce a heat shock; plots were sown in triplicates and an ambient chamber and an uncovered plot were included. Genotypes that maintained adaptation in the heat chambers were subsequently evaluated for reproductive stage high-temperature tolerance in the glasshouse under controlled conditions. The methodology was effective in identifying genotypes with high and repeatable heat tolerance. There was a positive correlation between yield under late sowing and yield in the heat chambers. The heat shock induced at anthesis under the heat chambers significantly reduced yield and seed number. However, no difference was observed between the ambient chamber and uncovered treatments for any trait. Genotypes deemed heat tolerant and that maintained seed number under the heat chamber induced heat shock also maintained seed number when evaluated in controlled glasshouse conditions.