Abstract
Fusarium head blight (FHB), primarily caused by Fusarium graminearum, threatens barley production in Idaho, the nation’s leading producer. The disease causes economically significant yield and quality reductions. Above set thresholds, mycotoxins such as deoxynivalenol (DON) in infested grains can result in downgrading or rejection upon sale. The present study screened a panel of Idaho-adapted USDA-ARS spring barley breeding lines for FHB reaction to generate susceptibility information and examine phenotypic trait correlations, followed by a genome-wide association study (GWAS). The panel was evaluated at three inoculated nurseries located in Kimberly, ID; Fargo, ND; and Sidney, MT. Two disease reaction traits, FHB index and DON concentration, and two influential agronomic traits, plant height and heading date, were assessed. Genotyping was conducted using the Illumina 50k Barley iSelect SNP Array. A minor allele frequency (MAF) >0.05, heterozygosity <0.10 and a call rate >0.90 were used for SNP quality control filtering. The effects of environment, genotype, and genotype-by-environment were highly significant for FHB reaction (P <0.001). Moderate correlations were found between FHB index and DON accumulation. Better FHB resistance was often observed in taller, later heading lines. Broad sense heritability estimates are 0.52, 0.57, and 0.55 for FHB index, and 0.53, 0.72, and 0.59 for DON concentration at the Kimberly, Sidney, and Fargo nurseries, respectively. At Kimberly, no lines were characterized as susceptible (S) or very susceptible (VS), and only 10% were moderately susceptible (MS). At Sidney, 61% were S and 17% VS and at Fargo, 47% were MS, 41% S, and 10% VS. A total of 97 marker-trait associations (MTAs) were identified for FHB index, with 80 on chromosome 2H, one on 1H, 3H, and 4H, two on 5H and 12 on 7H. For DON accumulation, 43 MTAs were identified, with 34 on chromosome 7H, two on 1H, 2H, 4H, and 5H, and one on 3H. Notably, MTAs at 506.18 Mbp on 3H for FHB index and 656.39 Mbp on 5H for DON accumulation represent QTL independent of agronomic traits, FHB_3H_4 and FHB_5H_5, respectively. Marker-trait associations for DON accumulation on 1H at 523.73 Mbp and on 2H at 704.37 Mbp, were independent of agronomic traits and have not been previously reported. The panel demonstrated adequate FHB resistance at the Kimberly nursery, but the humid environments found in Fargo and Sidney diminished resistance levels, suggesting that an unusually precipitous year in Idaho could yield similar results. Our study demonstrated FHB reaction variability within the panel that can be utilized in conventional breeding for FHB resistance and numerous pathways for marker-assisted selection targeting QTL independent of agronomic traits.