Taxonomic relationships among the toxigenic speciesFusarium acuminatum,Fusarium sporotrichioidesandFusarium tricinctumby isozyme analysis and RAPD assay

Abstract

Isozyme and random amplified polymorphic DNA (RAPD) analyses have been used in combination with numerical taxonomy to study the taxonomic relationships among the toxigenic species Fusarium acuminatum Ellis & Everh. sensu Gordon (subsp. acuminatum and subsp. armeniacum), Fusarium sporotrichioides Sherb. and Fusarium tricinctum (Corda) Sacc. Eight enzymes, selected among 23 enzyme systems tested initially for activity, resolution, and consistent formation of bands, were used for isozyme analysis of 75 strains. Both cluster analysis grouping by average linkage method and correspondence analysis of the isozyme data set resulted in an arrangement of the four taxa inconsistent with their classical taxonomic classification in the Fusarium sections Gibbosum and Sporotrichiella. Isolates of F. acuminatum subsp. acuminatum were more closely related to F. tricinctum than to F. acuminatum subsp. armeniacum. Correspondingly, the F. acuminatum subsp. armeniacum group was closer to F. sporotrichioides than to F. acuminatum subsp. acuminatum. Twenty-seven strains of the four taxa, representative of the variability found by isozyme analysis, were studied using a RAPD analysis with five different decamer primers. All the primers produced polymorphic amplification patterns with taxon-specific bands, in addition to individual-specific bands. Correspondence analysis of the RAPDs distinguished four compact groups corresponding to the four taxa studied. These data support the separation of the varieties of F. acuminatum into two different species, and suggest a revision of the Fusarium sections Gibbosum and Sporotrichiella may be necessary. Key words: Fusarium, isozymes, RAPDs, numerical taxonomy, mycotoxins.