Divergence of the IGS rDNA in Fusarium proliferatum and Fusarium globosum reveals two strain specific non-orthologous types

Abstract

A phylogenic analysis of Fusarium proliferatum
and closely related species was performed using the most
variable part within the intergenic spacer of the nuclear
ribosomal DNA (IGS) and compared with a previously
reported phylogeny performed in the same group of
samples with a partial region of the nuclear single copy
gene encoding the elongation factor 1α (EF-1α). The
phylogenies from both genomic sequences were not
concordant and revealed the presence of two nonorthologous
IGS types, named types I and II, in F.
proliferatum and Fusarium globosum.
Two specific PCR assays designed to amplify either IGS
type I or type II revealed that only one IGS type was
present in each individual in these two species. The
presence of both IGS types at the species level indicates
that homogenization has not been achieved yet. This might
be retarded if panmictic sexual reproduction was affected
by certain levels of clonal reproduction and/or by the
diverse hosts that these species are able to colonize. This
study indicates that taxonomic studies carried out with the
IGS rDNA, which has been widely used in Fusarium,
should be undertaken with caution.