Genetic structure and genome-wide association study of a genomic panel of two-row, spring barley (<i>Hordeum vulgare</i> L.) with differential reaction to Fusarium head blight (<i>Fusarium graminearum</i> Schwabe) and deoxynivalenol production

Fusarium head blight (FHB), primarily incited by <i>Fusarium graminearum</i> Schwabe, is the most devastating disease of barley (<i>Hordeum vulgare</i> L.) in Canada. Contaminated grains are unsuitable for use as livestock feed or by the malting industry, primarily due to contamination by mycotoxins such as deoxynivalenol (DON). Reducing DON content has been a long-term goal of barley breeders; however, the complex genetics of resistance and laborious testing required have made it difficult to develop resistant cultivars. An Illumina 50 K SNP beadchip was used to genotype a diverse collection (n = 400) of two-row barley genotypes, selected primarily from North American-breeding programs. This genomic panel was phenotyped in three environments in Manitoba, Canada, over two growing seasons. Genotypes were evaluated for heading date, height, FHB score, and DON content. A genome-wide association study (GWAS) was carried out using a mixed linear model (<i>MLM: Q</i> + <i>K</i>) accounting for population structure (<i>Q</i>) and kinship (<i>K</i>) as covariates. This study characterized the population structure of two-row barley germplasm important to North American-breeding programs. Significant marker-trait associations were identified on all chromosomes for FHB, and on all chromosomesexcept 1 H and 6 H for DON content. Individual marker effects were small, explaining only up to 5% of the phenotypic variation. Genes within genomic regions that were associated with FHB-related traits displayed multiple functions linked with disease resistance. While numerous minor, marker-trait associations were identified, phenotypic evaluations are still the best predictors of these traits, despite their time-consuming nature and dependenceon environmental conditions.