Meta-Analysis of Wheat QTL Associated with Heat and Drought Tolerance.

Heat and drought are the two most important environmental constraints to global wheat production, are often present simultaneously and will become more severe with global climate change.  A number of recent studies have reported quantitative trait loci (QTL) associated with heat and drought tolerance in wheat, as well as QTL for stress adaptive traits such as the availability of stem carbohydrates and crop canopy temperature.  While QTL mapping provides insight into the genetic control of a trait, the importance of the detected regions in additional genetic backgrounds is often unknown.  The goal of this study was to conduct a meta-analysis of wheat genome regions associated with heat and drought tolerance in order to identify QTL that were consistently detected across a range of environments and genetic backgrounds.

        To identify Meta-QTL (MQTL), a QTL database was developed from 30 studies targeted at heat and drought stressed environments.  The positions of individual QTL were projected onto a consensus genetic map based on the presence of common molecular markers and a 95% confidence interval (CI) was calculated for each QTL. After positioning the individual QTL, the software ‘Biomercator v2.1’ was used to predict the location and CI of MQTL based on maximum likelihood.  In total, 854 QTL were reported for 80 different traits.  This included 502 drought stress, 234 heat stress, and 118 adaptive trait QTL in non-stressed environments.  These QTL were grouped into 66 MQTL regions distributed throughout the wheat genome.  Most regions co-localized for both heat and drought stress, although both drought and heat stress specific MQTL regions were also identified.  Using the traits present within MQTL it was possible to genetically model Stress Trait Expression Pathways (STEPs) that can be used to identify target alleles and physiological traits for improvement through breeding.