Genetic Mapping of Quantitative Trait Loci Contributing to Variation in In Vitro Deoxynivalenol Levels in Fusarium...

Fusarium head blight (FHB) caused by Fusarium graminearum is a major disease of wheat and barley worldwide. Besides causing yield loss, F. graminearum also contaminates infected grains with trichothecene mycotoxins such as deoxynivalenol (DON) and its acetylated derivatives. Field isolates of F. graminearum vary in the amount of mycotoxins produced, both on infected wheat heads and in controlled laboratory experiments. Genes encoding the enzymes responsible for trichothecene mycotoxin biosynthesis are already characterized, but additional genes responsible for the variation in amounts of mycotoxins detected within and among populations remain to be identified. We measured levels of trichothecenes produced in vitro in a sample of 151 F. graminearum field isolates. Genome-wide association performed with these measurements identified 10 quantitative trait loci (QTL) associated with variation in DON and/or 15ADON levels. The candidate regions contain many functionally characterized genes, including the Swr1p helicase gene, an MFS transporter, and multiple other transmembrane transporters that may relate to the fungus' ability to transport trichothecenes across membranes for sequestration or export. These results help to characterize the genetic factors that influence variability in trichothecene levels, which contribute to our understanding of trichothecene levels on infected grain and may lead to strategies to mitigate this toxin contamination.