Identification of germplasm and genomic markers associated with reduced T-2 and HT-2 mycotoxin accumulation in oat

Harmful T-2 and HT-2 mycotoxins are produced by Fusarium langsethiae and Fusarium sporotrichioides in developing oat (Avena sativa L.) grain. This study identified oat genotypes with consistently low toxin accumulation across environments. Toxin enzyme-linked immunosorbent assay and fungal DNA (quantitative polymerase chain reaction) levels were quantified in 19 oat genotypes grown at two Irish sites under natural infection. F. langsethiae and T-2 + HT-2 were detected at both sites, while F. sporotrichioides was absent. Genotype effects were significant for both F. langsethiae DNA and toxin levels, and the traits were positively correlated (Spearman's ρ = 0.62, p < 0.001). Eleven genotypes were also evaluated in an F. langsethiae-inoculated glasshouse experiment within a larger panel of 190 genotypes. Across field and glasshouse environments, toxin levels were consistently low in Tempo, Sandy, and Jokikyla ME0501 and high in Stormont Arrow. Glasshouse T-2 + HT-2 levels ranged from below detection to 1000 µg kg^{- 1}. genome-wide association study using 4881 single-nucleotide polymorphisms identified five significant markers on Mrg11, mapping to two loci on chromosomes 6A and 4C associated with reduced toxin accumulation. The 6A locus was near HIPP39 (where HIPP is heavy metal-associated isoprenylated plant protein), whereas no coding genes occurred within ± 30 kb of the 4C locus. These associations were detected in only one of the two glasshouse runs and differed from loci previously identified under field conditions, highlighting the need for a better understanding of the elusive and variable nature of Fusarium-oat interactions. These results highlight genotypes and candidate loci to support breeding for reduced T-2 and HT-2 risk in oats.