Development of a PCR-based diagnostic assay for the specific detection of the entomopathogenic fungus Metarhizium anisopliae var. acridum

The entomopathogenic fungus Metarhizium anisopliae var. acridum is registered as a mycopesticide for acridid control in Africa and Australia. Traditionally, identification of M. anisopliae var. acridum infection in grasshoppers and locusts has relied upon development of fungal growth in infected cadavers. Conventional methods of detection of this entomopathogen in the environment and non-target organisms have been based on culture and bioassay. A PCR-based method for the detection of M. anisopliae var. acridum was developed. Sequence data from the distinct ITS rDNA regions facilitated the design of PCR primers that were used in PCR-based diagnostic assays for the detection of fungal DNA. The amplified sequence was 420 bp in length and specific to M. anisopliae var. acridum. Isolates of M. anisopliae var. anisopliae and M. flavoviride produced no PCR product with these primers. Other fungal entomopathogens, plant pathogens, mycopathogens, and soil saprophytes were also not detected by the pathogen-specific primers. The assay was also effective for the detection of M. anisopliae var. acridum DNA in the presence of soil DNA extracts and in infected grasshoppers.