Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 2, 2006
Publication Date: August 29, 2007
Citation: Bischoff, J., Humber, R.A., Rehner, S.A. 2007. Metarhizium frigidum sp. nov.: a cryptic species of m. anisopliae and a member of the m. flavoviride complex. Mycologia 98:737-745.
Insect-parasitic fungi classified as Metarhizium anisopliae attack a wide range of agricultural pest insects that annually inflict heavy economic losses to U.S. crops. The applied use of Metarhizium species as biological insecticides can potentially reduce the expense and environmental risks posed by chemical pesticides. In this study, we examined the status of Metarhizium anisopliae var. frigidum by determining its relationship to Metarhizium flavoviride using DNA sequence data. Results of these analyses demonstrate that these two varieties are evolutionarily distinct from one another and Metarhizium anisopliae . The species Metarhizium frigidum is described on the basis of its morphological and molecular characteristics. The results are significant because they provide new tools for identification within this group of fungi. This research will be used by scientists developing environmentally safe strategies for managing agricultural insect pests.
The anamorph genus Metarhizium is composed of arthropod pathogens, most with broad geographic and host ranges. Members of the genus, including “M. anisopliae var. frigidum” nomen nudum and Metarhizium flavoviride, have been used extensively as biological insecticides. In a recent revision of the genus, the variety “M. anisopliae var. frigidum” was suggested to be a synonym of M. flavoviride based largely on ITS sequence. In this study we performed multi-gene phylogenetic analyses using EF-1 alpha, RPB1, and RPB2 and morphologically evaluated strains of M. flavoviride and M. anisopliae var. frigidum. Included in these evaluations were the ex-type of M. flavoviride var. flavoviride and what would be considered the ‘ex-type’ of the invalidly published variety “M. anisopliae var. frigidum”. We conclude that “M. anisopliae var. frigidum” is distinct from M. flavoviride and warrants the recognition of a species. Based on morphological and molecular evidence the taxon M. frigidum sp. nov. is described.