Improving water use efficiency and drought tolerance in UK winter wheats

Abstract

Wheat yields in the UK are often limited by water deficit during critical stages of crop development. The aim of this project was to provide information that could help guide the identification and development of varieties with greater drought tolerance (DT). A genetically diverse set of 120 wheat varieties was evaluated under irrigated and managed drought conditions in the field. There was significant variation for DT index (DTI), water use efficiency (WUE), yield potential and yield stability. Although the ranking of varieties differed with each year, several varieties showed consistently better than average DTI, and another set poorer than average. There was significant variation between varieties for anatomical and physiological traits associated with performance under water-limited conditions. Each trait, however, explained only a small proportion of the variance in DT or WUE. The combination of traits that describes a superior water-efficient variety, which blends resilience with yield potential, could aid breeding by focusing selection for secondary (proxy) traits, or via molecular markers linked to these traits.

The project also examined the relative ranking of 64 varieties tested across a range of sites that differed in soil water holding capacity. Unfortunately, insufficient drought developed on enough sites to adequately determine consistent differences in the performance of varieties for dry conditions. However, the approach has merit if data on varieties are accumulated across sites and years.

To help understand the genetic control of DT, WUE and component traits, 135 lines were genotyped using 11 diagnostic markers plus seven markers based on published QTL data. A subset of 94 lines was genotyped using 2499 DArT biallelic dominant markers. These genotypic data, in conjunction with the phenotypic data collected from the field experiments, could be used in future association studies to discover the genetic basis of traits controlling DT and WUE.

These results provide a comprehensive and quantitative description of UK winter wheat lines for DT, WUE and traits associated with improved yields under dry conditions. However, the ranking of varieties depended on which measure of DT was used, and the timing and severity of the water deficit. The data gathered in this study confirms previous findings, suggests possible new avenues for genetic improvement, and provides a foundation for further work.