Association Mapping of Drought Tolerance Candidate Genes in Spring Wheat

Although many drought tolerance-related genes have been reported, functional markers are available for only a few of them. The objective of this study was to associate single nucleotide polymorphisms (SNPs) within drought tolerance candidate genes with phenotypic traits. Three drought tolerance candidate genes (Dehydration-Responsive Element Binding 1A, DREB1A; Enhanced Response to ABA, ERA1; and Fructan 1-exohydrolase, 1-FEH), were amplified and sequenced from 126 lines of spring wheat, using genome-specific primers. The lines were evaluated for phenotypic traits in 2010 and 2011 under a range of moisture conditions in Colorado, USA and Ethiopia.  SNP-trait associations were conducted using mixed and general linear models, taking into account population structure and genetic relatedness based on DArT markers. Associations of DREB1A with harvest index, kernel number per spike, spikelets per spike, spikes m^-2, final biomass, leaf senescence and flag leaf width were relatively consistent across environments. The 1-FEH gene amplified from the A genome showed stable associations with harvest index, yield, NDVI, green leaf area and flag leaf area across environments at P<0.05. However, 1-FEH from the B genome was associated with few traits and the associations were inconsistent. ERA1 from the A genome was associated with yield, kernel number, spikes m^-2, grain filling duration and plant height, whereas ERA1 from the B genome was associated with days to heading, days to maturity, flag leaf width, thousand kernel weight and kernel number. Generally, the current study showed that each evaluated gene had minor effects on multiple traits under both dry and irrigated conditions.