A field-based technique for screening heat tolerance of wheat lines differing in maturity at matched developmental phases

Field-based screening of heat tolerant wheat germplasm is complicated by confounding effects of phenological differences between genotypes at the timing of natural heat events. Here, we developed and tested during two years at three locations and at different sowing dates, a novel technique, which allows field screening of diverse wheat genotypes at matched developmental stages. Wheat genotypes were planted in single rows and artificial light was provided at the end of the rows extending the photoperiod. This supplemental light induced a gradient of flowering time along the rows for each genotype, so that genotypes could be tagged at a closely matched developmental phase. The method was found to facilitate comparison of all tested genotypes at a matched developmental stage when heat events occured. The novel technique resulted in robust genotype rankings for heat-tolerance that were relatively stable across environments subjected to similar heat stress. The method has potential to improve the efficiency of heat-tolerance field screening, and to breed for germplasm with heat tolerance