Genetic diversity of Australian Fusarium pseudograminearum populations causing crown rot in wheat

Fusarium crown rot (FCR) caused by the fungus Fusarium pseudograminearum (Fp) is an important disease of wheat that reduces yield and grain quality in many countries, including Australia. In this study, we investigated mating type idiomorph composition, putative chemotype and population genotypic structure of 98 Fp isolates from Western Australia (WA) and the eastern Australian states of New South Wales, Victoria and South Australia. Our results revealed the expected 1:1 mating type ratio for isolates from the eastern states while there was significant variation to a 1:1 mating type composition with isolates from WA. A chemotype-specific PCR assay indicated that all Fp isolates from eastern states and WA segregated for the 3-ADON trichothecene chemotype. Genetic diversity assessed using 21 cleaved amplified polymorphic sequence markers revealed a high level of genotypic variation within and between Fp populations from eastern Australian states and WA. Analysis of molecular variance (AMOVA) showed significant difference between populations from eastern states and WA. The genetic diversity measured by Shannon index ranged from 0.95 to 2.30 with the lowest and highest values detected in Hart and Rowena populations, respectively in the eastern states. Index of association analysis showed no significant linkage of markers among isolates within 60% of the populations, suggesting that sexual reproduction may be occurring in the pathogen from those locations. These results improve understanding of Fp population dynamics across Australia and highlight the importance of monitoring for shifts in the population which could have implications for disease management.