Trichothecene genotypes of Gibberella zeae from winter wheat fields in the eastern USA

Fusarium head blight (FHB), caused principally by Gibberella zeae (Fusarium graminearum), is a devastating disease of small grains such as wheat and barley worldwide. Grain infected with G. zeae may be contaminated with trichothecene mycotoxins such as deoxynivalenol (DON) and nivalenol (NIV). Strains of G. zeae that produce DON may also produce acetylated derivatives of DON: 3-acetyl-DON (3-ADON) and 15-acetyl-DON (15-ADON). Gradients (clines) of 3-ADON genotypes in Canada have raised questions about the distribution of G. zeae trichothecene genotypes in wheat fields in the eastern USA. Tri3 and Tri12 genotypes were evaluated in 998 isolates of G. zeae collected from 39 winter wheat fields in New York (NY), Pennsylvania (PA), Maryland (MD), Virginia (VA), Kentucky (KY) and North Carolina (NC). Ninety-two percent (919/998) of the isolates were 15-ADON, 7% (69/998) were 3-ADON, and 1% (10/998) was NIV. A phylogenetic analysis based on portions of three genes (PHO, RED and URA) from 23 isolates revealed two species of Fusarium (F. graminearum sensu stricto and one isolate of F. cerealis (synonym F. crookwellense)). An increasing trend of 3-ADON genotypes was observed from NC (south) to NY (north). Punctuated episodes of atmospheric transport may favour a higher frequency of 3-ADON genotypes in the northeastern USA, near Canada, compared with the mid-Atlantic states. Discoveries of the NIV genotype in NY and NC indicate the need for more intensive sampling in the surrounding regions.