Fusarium graminearum causes Fusarium head blight, a devastating disease of wheat and barley. The pathogen also contaminates infected grains with the mycotoxin deoxynivalenol (DON), making them unsuitable for food and feed. The objective of this study is to identify the genetic basis of variation in ascospore and mycotoxin production using genome-wide association (GWAS). Fusarium graminearum overwinters on crop debris, and under favorable conditions produces perithecia, the pathogen’s sexual fruiting bodies. The perithecia produce ascospores, which are the primary source of infection in the field. DON, besides having health consequences, is also a virulence factor. Genes responsible for the biosynthesis of DON and its derivatives cluster in three TRI loci, but genes outside the TRI loci may affect the amount of DON produced by different isolates. We measured ascospores and mycotoxins (DON and 15ADON) produced by 152 isolates in controlled laboratory experiments. Ascospores were collected from cultures grown on carrot agar plates and counted. The amounts of DON and 15ADON produced from isolates grown on rice cultures were measured using GC-MS. GWAS was conducted using the models implemented in two R packages. We identified 14 SNPs significantly associated with ascospore production, six of which were identified by more than one model. SNPs associated with ascospore production are located in, or in close proximity to, a secondary metabolite biosynthesis cluster and genes that code for various proteins, including: a peroxisomal-coenzyme A synthetase, a copper transporter, and a permease. Similarly, eight SNPs were significantly associated with DON, and three with 15ADON production. One associated SNP is common to DON and 15ADON production and falls in a polyketide biosynthesis gene cluster. Other associated SNPs are found in, or are in linkage disequilibrium with, SNPs in: an efflux family gene or genes that code for a non-ribosomal peptide synthetase and an MFS transporter. Many associations we identified are novel and provide new candidates for functional studies. Once verified, they can be used as markers to monitor field populations for their ascospore and DON production potential, which can further inform management decisions.

Acknowledgement and Disclaimer

This material is based upon work supported in part by the U.S. Department of Agriculture under Agreement No. 59-0206-2-162. This is a cooperative project with the U.S. Wheat & Barley Scab Initiative. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture.