This study was conducted to assess evolutionary relationships, species diversity and trichothecene toxin potential of five Fusarium graminearum complex (FGSC) isolates identified as genetically novel during prior Fusarium head blight (FHB) surveys in Nepal and Louisiana. Results of a multilocus genotyping (MLGT) assay for B-trichothecene species determination indicated these isolates might represent novel species within the FGSC. GCPSR-based phylogenetic analyses of a 12-gene dataset, comprising portions of seven loci totaling 13.1. kb of aligned DNA sequence data, provided strong support for the genealogical exclusivity of the Nepalese and Louisianan isolates. Accordingly, both species are formally recognized herein as novel FGSC species. Fusarium nepalense was resolved as the sister lineage of Fusarium ussurianum+. Fusarium asiaticum within an Asian subclade of the FGSC. Fusarium louisianense was strongly supported as a reciprocally monophyletic sister of Fusarium gerlachii+. F. graminearum, suggesting that this subclade might be endemic to North America. Multilocus Bayesian species tree analyses augment these results and provide evidence for a distinct lineage within F. graminearum predominately from the Gulf Coast of Louisiana. As predicted by the MLGT assay, mycotoxin analyses demonstrated that F. nepalense and F. louisianense could produce 15ADON and nivalenol, respectively, in planta. In addition, both species were only able to induce mild FHB symptoms on wheat in pathogenicity experiments.
Bibliographical noteFunding Information:
Special thanks are due Stacy Sink and Nathane Orwig for excellent technical support and Yanhong Dong, Mycotoxin Laboratory, University of Minnesota, for the GC/MS mycotoxin analyses. BAJS specifically thanks Joseph Brown, Jack Sullivan, David Tank, Luke Harmon, and Travis Hagey for helpful discussion. IBEST Bioinformatics facilities are supported by NIH/NCRR P20RR16448 and P20RR016454. LRG and HCK acknowledge that a portion of this research was supported by the US Department of Agriculture under Agreement No. 59-0790-7-074, a cooperative project of the US Wheat & Barley Scab Initiative. The mention of firm names or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other firms or similar products not mentioned. The USDA is an equal opportunity provider and employer.
- Fusarium head blight
- Genealogical concordance
- Reciprocal monophyly