A taxonomic revision of Metarhizium based on a phylogenetic analysis of rDNA sequence data

Abstract

The taxonomy of Metarhizium has been reassessed using sequence data and RAPD patterns from 123 isolates recognised as M. anisopliae, M. flavoviride or M. album. A high level of genetic diversity was found which was best resolved at the species/variety level by sequence data from the ITS and 28S rDNA D3 regions. RAPD patterns correlated closely with the sequence data and revealed a much greater degree of diversity useful for distinguishing strains within a variety. Ten distinct clades were revealed by the cladogram based on the combined sequence data set. Several major evolutionary lines were revealed, but the taxonomic relationships at the base of the tree are poorly resolved. The data support the monopoly of the M. anisopliae group, and recognise four clades within it. Two correspond with M. anisopliae var. anisopliae and M. anisopliae var. majus. The other two are described as new varieties based on their distinctive ITS sequence data: M. anisopliae var. lepidiotum and M. anisopliae var. acridum vars nov. M. album, M. flavoviride var. flavoviride and M. flavoviride var. minus are recognised and redefined according to ITS sequence data. Three clades represent two new varieties, M. flavoviride var. novazealandicum and M. flavoviride var. pemphigum vars nov., based on their distinct ITS sequence data. The third, with two isolates, has not been named pending further data.