Taxonomic novelties in Aspergillus section Fumigati: A-tasmanicus sp nov., induction of sexual state in A-turcosus and overview of related species
Abstract
The phylogenetic position of two Aspergillus strains isolated from Australian soil and phenotypically resembling A. unilateralis was investigated by using multigene phylogeny based on beta-tubulin (benA), calmodulin (CaM), actin (act), and RNA polymerase II second largest subunit (RPB2) genes. The analysis supported their placement into a separate lineage within a well-supported clade containing 10 other members of section Fumigati ("A. unilateralis clade'').
Comparisons of extrolite profiles, taxonomically informative morphological and physiological characters were made, and it was discovered that the two strains can be differentiated from all relatives by their low maximum growth temperature, short stipes, and ornamentation of conidia. The data justified the proposal of a new species, A. tasmanius sp. nov.
Amplification of mating-type genes showed that the A. unilateralis clade contains five heterothallic species. Only the MAT1-1-1 idiomorph was detected among isolates of A. unilateralis, A. tasmanicus, and A. marvanovae, while isolates having both opposite mating types were detected in A. turcosus and A. nishimurae.
The sexual state of A. turcosus was induced by mating experiments and is described in this study. Ascospores of this species were unique by their smooth to finely verrucose convex surface and two well-visible equatorial crests.
Some exometabolites detected in A. marvanovae and A. tasmanicus are also indicative of a perfect state, thus supporting the hypothesis that these species have cryptic sexual cycles. The epitype and ex-epitype culture is designated for A. nishimurae to facilitate further taxonomic work with this species.