Managing Fusarium Head Blight (FHB) caused by Fusarium graminearum sensu stricto and other members of the F. graminearum species complex (FGSC), is challenging due in part to the diversity of genetic factors impacting disease severity and toxin accumulation. In North America, FHB is primarily caused by three populations of F. graminearum ss. The NA1 population mainly produces the trichothecene toxins DON and 15ADON, while NA2 mostly produces 3ADON instead of 15ADON. The NA2 population has been advancing across the Eastern U.S. and Canada, and it has been hypothesized that 3ADON confers higher aggressiveness, toxigenicity, and competitiveness than 15ADON. The present study has three objectives (i) investigate whether toxin chemotype and other genetic markers segregate according to Mendelian principles among progeny resulting from crosses between different populations of F. graminearum, (ii) assess differences in aggressiveness, toxigenicity, and competitiveness among individuals and mixtures of progeny resulting from outcrosses in susceptible and moderately resistant wheat, with or without fungicides, (iii) identify DNA markers associated with aggressiveness and toxigenicity by analyzing whole genome sequence data derived from pools of progeny exhibiting variation in these traits. A self-sterile mating tester strain of F. graminearum, generated by deleting the MAT1-1-1 locus in the NA1-15ADON strain PH-1, was crossed with NA2-3ADON, NA3-NX2, and NIV strains. The parents were selected from 19 strains collected from different locations in the United States based on morphology, fertility, and ascospore viability. The NA2-3ADON and NA1-15ADON parents were more aggressive on wheat than the NA3-NX2 and NIV parents. The NA2-3ADON parent produced more mycotoxin than the other parental strains. Ninety-three progeny were randomly chosen from the NA1-15ADON:NA2-3ADON cross, and tested using primers for the MAT1-1-1 and chemotype loci. The progeny displayed anticipated Mendelian segregation patterns for both primer sets. Subsequently, 80 of the 93 were chosen for additional assays, including disease severity and mycotoxin production on Wheaton and Alsen wheat varieties. This study will provide new insights into the complex genetics of pathogenicity and aggressiveness of F. graminearum and the role of chemotype and generate tools for further research aimed at improving management of this important pathogen.
Acknowledgements: This material is based upon work supported by the U.S. Department of Agriculture. 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 author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.