The Phenotype-Genotype Connection: Association Mapping for Yield, Growth Habit, and Adaptation Traits in Wheat

Molecular dissection of the genetic architecture underlying yield and adaptation through whole-genome strategies is crucial to further the potential for breeding wheat varieties that are higher yielding and more adapted to target environments. Genome-wide association studies (GWAS) use the concept of linkage disequilibrium (LD) to find associations between marker genotypes and phenotypic trait variation. In the current study, GWAS using data from the Illumina 9K iSelect SNP assay is being carried out on a collection of 240 soft red winter wheat (SRWW) cultivars and breeding lines evaluated for agronomic traits across multiple locations from the 2014-2016 seasons. The effects of allelic variation for major growth habit loci, namely vernalization (Vrn), photoperiod (Ppd), and height (Rht), and their combinations to yield, heading date, and height of the SRWW panel are also being examined using allele-specific SNP markers. GWAS revealed the presence of 78 significant marker-trait associations in key chromosomal regions of the wheat genome for yield and agronomic traits in the 2014 season. Significant marker loci contributed approximately 4-14% of the variation for measured traits. Preliminary marker analyses indicated significant effects of Ppd-B1, Ppd-D1, and Rht-D1 on height and heading date. Allelic diversity for the major growth habit genes was also observed for the panel, a characteristic of the diverse nature of the population under study. A genotyping-by-sequencing (GBS) approach will be used to increase the depth of marker coverage for GWAS. Results of this study are anticipated to facilitate marker-assisted selection towards breeding cultivars of wheat with higher genetic potential.