Metarhizium Brunneum

''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.

Genome

The genome of ''M. brunneum'' was the first in the genus to be completely assembled. The 7 chromosomes and mitogenome have a total sequence length of 37,796,881. The sequencing and assembly was performed at Swansea University in 2021.

Standard isolate and characteristics

Bischoff et al. /sup> 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.

Applications

Varroa mite (honeybees)

In 2021, a custom-bred strain of ''M. brunneum'' was created to target and kill the varroa mite that afflicts honeybee populations. That strain was bred to be heat-tolerant, raising the percentage of spores that germinated at 35 °C—the temperature of a typical beehive— from 44% to 70%. A second breeding effort increased the deadliness of the strain from 4% just over 60%.

Important isolates

* Isolate M.a. 43 (a.k.a. F52, Met52, 029056) primarily infects beetle larvae: and is the active ingredient of 'BIO 1020', originally developed for control of ''Otiorhynchus sulcatus'' and now 'Met52'; it is still often described in commercial literature as "''M. anisopliae''". Commercial products based on this isolate are subcultures of the individual isolate M.a. 43 and are represented in several culture collections including: Julius Kühn-Institute for Biological Control (previously the BBA), Darmstadt, Germany: .a. 43 HRI, UK: 75-86 (acronyms V275 or KVL 275) KVL Denmark VL 99-112 (Ma 275 or V 275) Bayer, Germany SM 3884 ATCC, USA TCC 90448 USDA, Ithaca, USA RSEF 1095 Granular and emulsifiable concentrate formulations based on this isolate have been developed by several companies and registered in the EU and N. America (US and Canada) for use against black vine weevil in nursery ornamentals and soft fruit, other Coleoptera,
western flower thrips in greenhouse ornamentals and chinch bugs in turf.

See also

* Biological insecticides

References

External links

Index Fungorum record
links to a list of synonyms

{{Authority control

Clavicipitaceae
Parasitic fungi
Fungi described in 1935
Taxa named by Thomas Petch
Fungus species