Kingdom Fungi Class Sordariomycetes Family Clavicipitaceae Rank Species | Division Ascomycota Order Hypocreales Genus Metarhizium | |
Similar Metarhizium, Metarhizium majus, Paecilomyces fumosoroseus, Metarhizium acridum, Metarhizium flavoviride | ||
Metarhizium brunneum, is the re-instated name of a group of reassigned Metarhizium isolates, previously grouped in the species "Metarhizium anisopliae var. anisopliae": based on a multigene phylogenetic approach using near-complete sequences from nuclear DNA. It is a mitosporic fungus with asexual reproduction, which was formerly classified in the form class Hyphomycetes of the form phylum Deuteromycota (also often called Fungi Imperfecti). M. brunneum has been isolated from Coleoptera, Lepidoptera, Diptera and soil samples, but a commercially developed isolate (below) has proved virulent against Hemiptera and Thysanoptera.
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Type isolate and characteristics
Bischoff et al.[1] state: "There is no viable ex-type culture for M. brunneum Petch. However ARSEF 2107 (from Oregon, USA) is considered an authentic strain because the taxon’s author, Petch, identified it and we designate it here as an ex-epitype. ... an ex-epitype (BPI 878297) derived from a living culture (ARSEF 1914) is designated for this taxon." Metarhizium brunneum is the most basal lineage in the clade called 'PARB' in which it appears impossible to differentiate isolates of M. brunneum from M. anisopliae, on morphological characteristics alone (with the exception of the presumptive colour mutant ARSEF 2107).
Conidia typically measure 4.5–8.0 µm long x 2.0–3.0 µm diameter: similar to several other Metarhizuim species. Petch designated a type collection from the Philippines, which he described as turning brown in mature colonies. This colour variant may occur regularly in nature based on the fact that Petch had identified a number of isolates as M. brunneum from geographically distant locations. However it is important to note that the majority of M. brunneum isolates examined by Bischoff et al. were olive-green in colour (similar to M. anisopliae), rather than the buff and tan pigmentation described for the type specimen and the ex-epitype cultures, respectively.