Mapping of Agronomic, Phenology-Related and Metabolic Traits in Wheat (Triticum aestivum L.) Grown in a Water-Limited Environment

Drought is responsible for yield losses and limitations of the growth of bread wheat in many parts of the world. Progress in breeding to improve complex multigene traits, such as drought stress tolerance, has been limited by high sensitivity to environmental factors, low trait heritability, and the complexity and size of the hexaploid wheat genome. In order to obtain further insight into genetic factors that affect yield under drought, we measured both primary (using gas chromatography-mass spectrometry, GC-MS) and secondary (using liquid chromatography-MS, LC-MS) metabolites as well as 29 agronomic traits using the doubled haploid population from a cross between drought-sensitive and drought-tolerant wheat cultivars grown in the field under terminal drought stress. A linear mixed model was used to partition and account for non-genetic and genetic sources of variation, and quantitative trait locus (QTL) analysis was performed. Comparison of the agronomic and metabolic trait variation uncovered novel correlations, including metabolites associated with either plant maturity-related or grain yield-related traits. As differences in plant phenology influenced correlations and QTL detection in the GC-MS experiment, the effects of five major phenology-related loci were introduced as cofactors in the LC-MS analyses, and were found to differ in their impact upon metabolic and agronomic traits. Previous results that demonstrate the importance of including plant phenology in the assessment of useful traits were reinforced. This approach proved valuable for identifying novel biomarkers for the performance of wheat under drought stress and could facilitate the identification of candidate genes involved in drought-related responses in wheat.