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Updated: Jun 21, 2026

Development of Metarhizium anisopliae as a Mycoinsecticide: From Isolation to Field Performance
Published on: July 30, 2017
Characterization of Metarhizium species and varieties based on molecular analysis, heat tolerance and cold activity
E K K Fernandes1, C A Keyser, J P Chong
1Department of Biology, Utah State University, Logan, UT, USA.
Aims:
The genetic relationships and conidial tolerances to high and low temperatures were determined for isolates of several Metarhizium species and varieties.
Methods And Results:
Molecular-based techniques [AFLP and rDNA (ITS1, ITS2 and 5.8S) gene sequencing] were used to characterize morphologically identified Metarhizium spp. isolates from a wide range of sources. Conidial suspensions of isolates were exposed to wet heat (45 + or - 0.2 degrees C) and plated on potato dextrose agar plus yeast extract (PDAY) medium. After 8-h exposure, the isolates divided clearly into two groups: (i) all isolates of Metarhizium anisopliae var. anisopliae (Ma-an) and Metarhizium from the flavoviride complex (Mf) had virtually zero conidial relative germination (RG), (ii) Metarhizium anisopliae var. acridum (Ma-ac) isolates demonstrated high heat tolerance (c. 70-100% RG). Conidial suspensions also were plated on PDAY and incubated at 5 degrees C for 15 days, during which time RGs for Ma-an and Ma-ac isolates were virtually zero, whereas the two Mf were highly cold active (100% RG).
Conclusions:
Heat and cold exposures can be used as rapid tools to tentatively identify some important Metarhizium species and varieties.
Significance And Impact Of The Study:
Identification of Metarhizium spp. currently relies primarily on DNA-based methods; we suggest a simple temperature-based screen to quickly obtain tentative identification of isolates as to species or species complexes.
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