Genetic basis of wheat yield under dry and hot climates

In Australian dryland agriculture, grain crop yields are approximately 50% of their potential and are highly unpredictable. During the 1990’s, the rate of productivity increase in Australian broad acre cropping improved by 3.4% annually but has since slowed and declined by -1.4% in drought years. A way to improve the drought tolerance of crops varieties is to discover new genes and alleles that allow plants to continue to grow and yield grain under water limited conditions. Although many quantitative trait loci (QTL) have been identified in wheat, few have been deployed in breeding programmes. We cumulated QTL over 10 years on three wheat populations for yield, agronomical, physiological and morphological traits in various locations in Australia, India and Mexico. Genomic resources now enable us make progress in fine mapping and positional cloning of QTL in wheat. Target QTL that increases yield and yield components in hot and dry climates were fine mapped to genes level using the cv Chinese Spring reference sequence and whole genome shotgun sequences of Australian parental lines. We also investigated QTL function under controlled conditions to measure growth rate, transpiration, stomatal traits, and semi-controlled evironments using deep soil bins, rainout shelter and irrigation. By measuring accurately the environmental variables and using ecophysiological models, we can dissect the response to the environment into elementary and simpler traits and identify the conditions where a QTL is specifically expressed. Such detailed information on QTL x environment interaction, physiological mechanism and fine mapping is crucial for breeding application.