A field and controlled environment evaluation of wheat (Triticum aestivum) adaptation to heat stress

Abstract

Heat stress is a major constraint on wheat (Triticum aestivum L.) production in many regions of the world. While research into heat stress tolerance has been conducted across many crop species, there are still significant gaps in our understanding of the impacts of heat stress on production, the level of genetic variation for heat stress tolerance in the field and the varying phenotypic responses to various yield components. Here, we report on the heat stress tolerance for 24 bread wheat (Triticum aestivum L.) genotypes which were evaluated across 13-environments over two growing seasons in the Mediterranean-type climate of southern Australia. Numerous climatic co-variates were measured to further understand interactions of temperature stress on crop performance. Not surprisingly, heat stress was found to have significant negative impacts on grain yield in field conditions, with reductions of 302 kg ha−1 ᵒC-1 for each day with maximum temperature in excess of 30ᵒC during anthesis and a reduction of 161 kg ha−1 ᵒC-1 for each day with maximum temperature in excess of 30ᵒC during grain fill. Genotype by environment interactions for grain yield performance under varying levels of heat stress were also observed in the field, suggesting that plant breeding selection strategies could be used to improve adaptation to heat stress. Additionally, all genotypes were phenotyped using a controlled environment assay (plants exposed to an air temperature of 36ᵒC and a wind speed of 40 km h−1 for three consecutive, eight-hour days, 10 days post the end of anthesis). Significant differences in genotype performance for leaf senescence and leaf chlorophyll content in response to heat stress were identified under the controlled environment conditions. Further evaluation showed that some of the field genotype by environment interaction for heat stress tolerance could be explained by performance under controlled environment conditions. This suggests that detailed physiological studies in controlled environment conditions do relate to performance in field conditions.