Department of Plant Pathology, North Dakota State University, Fargo 58108-6050.
Fusarium head blight (FHB) is primarily caused by Fusarium graminearum in North America. Isolates of F. graminearum can be identified as one of three chemotypes: 3-acetyl-deoxynivalenol (3ADON), 15-acetyl-deoxynivalenol (15ADON), and nivalenol (NIV). In this study, we characterized F. graminearum isolates collected in 1980 to 2000 (old collection) and in 2008 (new collection) from North Dakota and found a 15-fold increase of 3ADON isolates in the new collection. Evaluation of randomly selected 3ADON isolates and 15ADON isolates on three spring wheat genotypes (Grandin, Steele-ND, and ND 2710) by single-floret inoculation indicated that the 3ADON population caused a higher disease severity and produced more DON at a significant level than the 15ADON population on Grandin (susceptible to FHB) and ND 2710 (with FHB resistance from Sumai 3). However, no significant differences in disease severity and DON production were observed between the two populations on Steele-ND (with moderate resistance from Triticum dicoccoides). The 3ADON isolates also exhibited a higher DON production in rice culture and produced more spores on agar media than the 15ADON isolates, suggesting a fitness advantage of the newly emerging 3ADON population over the prevalent 15ADON population. Population genetic analyses using DNA markers revealed a significant genetic differentiation between the two populations. The information obtained in this study could have an impact on development of FHB-resistant wheat cultivars and disease management.