Genotype–phenotype relationships for high-temperature tolerance: an integrated method for minimizing phenotyping constraints in wheat

Various attempts have been made to understand the traits and genes associated with heat stress tolerance in wheat (Triticum aestivum L.) in the field and under controlled conditions. Attempts made under controlled conditions have not been conclusive, mainly through a lack of sufficient precision in simulating the ambient temperature dynamics and microenvironments prevalent in the field. In addition, inconsistency in field phenotyping is a major concern. Hence, we attempted to develop a method for phenotyping wheat for heat stress tolerance through a novel temperature-controlled phenotyping facility (TCPF), along with an inexpensive tool to ensure uniform crop establishment. The objective was to improve the precision of assessing plants’ responses to elevated temperatures, particularly when these experiments are challenged by a large number of genotypes to be screened that show significant variations in their phenology. The study involved 75 genotypes from a recombinant inbred line population with differing responses to heat stress under three conditions: in the TCPF and in the field [regular field season and late sown (LS)] across two consecutive years. The results revealed that the yield components were different under LS and TCPF conditions. These differences reflected the plants’ responses to morphophenolog-ical adaptations arising from the late planting time and were not really reflective of the heat stress response. However, greater precision in differentiating high-temperature responses in the TCPF was evident from the repeatability in terms of growth, physiology, and productivity. This could be attributed to uniform crop establishment and improved capacity to maintain the desired temperature for phenotyping.