Differentiation of species and strains of entomopathogenic fungi by random amplification of polymorphic DNA (RAPD)

Abstract

Polymerase chain reaction (PCR)-based technology, involving random amplification of polymorphic DNA (RAPD), was used to assess the genomic variability between 24 isolates of deuteromycetous fungi (Metarhizium anisopliae, Metarhizium flavoviride, unidentified strains of Metarhizium and Beauveria bassiana) which were found to infect grasshoppers or locusts. M. flavoviride showed little intraspecific variability in PCR-amplified fragments when compared to M. anisopliae. The high level of variability in PCR-amplified fragments contained within M. anisopliae was similar to the total variability between B. bassiana, M. anisopliae and M. flavoviride, and suggests that M. anisopliae may include a number of cryptic species. Four polymorphic RAPD fragments were used to probe the genomic DNA of the various species and strains. On the basis of these probes the fungi can be grouped into M. flavoviride, M. anisopliae, or B. bassiana. According to PCR-amplified fragments, previously-unidentified Metarhizium strains were characterized as M. flavoviride. There was little evidence that these fungi, all isolated from, or virulent towards, grasshoppers or locusts, showed host-selection in PCR-amplified fragments. Nor was geographical origin a criterion for commonalty based on PCR-amplified fragments. PCR-fragment-pattern polymorphisms and the construction of probes from one or more of these fragments may provide a useful and rapid tool for identifying species and strains of entomopathogenic fungi.