Phylogenetic relationship within Fusarium sambucinum Fuckel sensu lato, determined from ribosomal RNA sequences.

Partial ribosomal RNA nucleotide sequences were determined for 11 strains of Fusarium sambucinum Fuckel sensu lato to assess by molecular genetic means, Nirenberg's recent morphotaxonomic interpretation which split the species into three distinct taxa: F. sambucinum sensu stricto, F. torulosum, and one other species, as yet unnamed (Fusarium species nova). Four sequence patterns were identified among the 11 strains. Two sequences that varied at one site were found among strains of F. sambucinum, strains of F. torulosum and Fusarium sp. nov. showed no intraspecific variation. Interspecific comparisons revealed nucleotide sequence differences of 3-9 substitutions in the ca. 240 nucleotide rRNA segment examined. Although interspecific differences are not large in terms of percent nucleotide substitution, they are much larger than the observed intraspecific variation and support the morphological interpretation distinguishing three taxa. When the data were analysed using parsimony and bootstrapping, the three taxon tree was well supported. The phylogenetic arrangement of these strains is congruent with secondary metabolite profile similarities.