PHYLOGENETIC RELATIONSHIP WITHIN FUSARIUM-SAMBUCINUM FUCKEL SENSU-LATO, DETERMINED FROM RIBOSOMAL-RNA SEQUENCES

Partial ribosomal RNA nucleotide sequences were determined for 11 stra ins of Fusarium sambucinum Fuckel sensu lato to assess by molecular ge netic means, Nirenberg's recent morphotaxonomic interpretation which s plit the species into three distinct taxa: F. sambucinum sensu stricto , F. torulosum, and one other species, as yet unnamed (Fusarium specie s nova). Four sequence patterns were identified among the 11 strains. Two sequences that varied at one site were found among strains of F. s ambucinum, strains of F. torulosum and Fusarium sp. nov. showed no int raspecific variation. Interspecific comparisons revealed nucleotide se quence 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 t he observed intraspecific variation and support the morphological inte rpretation distinguishing three taxa. When the data were analysed usin g parsimony and bootstrapping, the three taxon tree was well supported . The phylogenetic arrangement of these strains is congruent with seco ndary metabolite profile similarities.