Submitted to: Mycotoxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 1997
Publication Date: N/A
Interpretive Summary: Species in the filamentous fungal genus Fusarium produce toxins that impact on human health and safety. Some of the most toxic strains ever discovered were isolated from diseased wheat and barley grown on the South islands of Japan, Kyushu and Shikoku. It is from these strains that the fungal toxins nivalenol, and nivalenol mono- and diacetate were first isolated. The purpose of this study was to characterize these strains using molecular genetic techniques in order to determine their identity and their relationships to other closely related toxigenic species of Fusarium. Results of these studies indicate that the toxigenic strains from Japan represent an undescribed species most closely related to a lineage of Fusarium that includes F. sambucinum. These results suggest that molecular genetics should prove to be an invaluable tool to investigate the origin of toxins within lineages and to predict toxin production for the many new pathogenic species of Fusarium that will be discovered over the next decade.
Technical Abstract: Phylogenetic relationships of important trichothecene-producing strains originally identified as Fusarium nivale Fn-2, Fn-3 and Fn-2B and F. episphaeria Fn-M were investigated within the Gibberella lineage of Fusarium using nucleotide characters obtained by sequencing polymerase chain reaction (PCR) DNA amplified from the following 4 loci: nuclear 28S ribosomal DNA, nuclear ribosomal internal transcribed spacer (ITS) region, mitochondrial small subunit (mtSSU) ribosomal DNA, and beta-tubulin gene exons and introns. Parsimony analysis of the individual and combined data sets indicate that Fn-2, Fn-3, Fn-2B, and Fn-M represent an undescribed species of Fusarium. Bootstrap and decay analysis identified a clade containing F. sambucinum and several other diacetoxyscirpenol (DAS) and/or T-2 trichothecene-producing species as a sister to Fusarium sp.n. The outgroup species used to root the tree, by contrast, produce a different set of mycotoxins that include deoxynivalenol and zearalenone. These results emphasize the importance of investigating the evolution of Fusarium toxins within the context of a robust species-level phylogeny.