QTL for canopy temperature response related to yield in both heat and drought environments

The effects of drought due to insufficient soil water supply frequently occur concurrently with high air temperature. These combinations of environmental conditions are likely to increase in frequency if climate change predictions are realised. While there have been studies of the effects of heat shocks and high temperatures at various stages of wheat reproductive growth, there are no published reports on genomic regions associated with responses to heat and drought conditions in the field. Experiments in north-west Mexico were grown as managed droughts (i.e. growing into full moisture profile) or were planted three months after the normal planting time and irrigated. Maximum daily temperatures in the heat trials were 7 to 10°C higher (> 30°C) than in the drought trials. Yields of a set of 167 recombinant inbred lines from the Seri-Babax cross were highly correlated (>0.59) among the experiments (two of each treatment, averaging 303 and 253 gm under drought and heat, respectively). Using composite interval mapping, cooler canopy temperatures and higher grain yields were associated with the Babax allele on linkage groups 1B, 3B and 4A under both drought and heat conditions. Cool canopy effects were also detected due to the Seri allele on linkage group 2B, but with no effect on yield. The effects of these QTL were to decrease canopy temperatures by 0.2 to 0.5°C in heat trials and by almost 1.5°C in one of the drought trials. The associated positive effects on grain yield ranged from 15 to 50 g m and included a positive effect due to the presence of the 1BS chromosome segment of Babax instead of the 1RS rye segment present in Seri.