Intraspecific variation of 25 Metarhizium anisopliae
var. anisopliae isolates from various insect hosts and geographical
origins was
studied using RFLP analysis of the rDNA gene complex and the mtDNA.
Heterologous and homologous mitochondrial and
ribosomal probes were used to produce RFLP profiles of the isolates.
The rDNA analysis allowed the differentiation of only seven
isolates but provided evidence for the possible presence of introns
in different sites of the nuclear rRNA-gene-complex. PCR
amplification of the ITS1-5.8S-ITS2 rDNA region and the mtDNA regions
corresponding to the SrRNA and the LrRNA, followed
by restriction analysis of the PCR products underlined the conserved
nature of these regions. By contrast, digestion with any one of
endonucleases Hae III, Cfo I, Hpa II and
subsequent RFLP analysis of the mtDNA, allowed the classification of the
25 isolates in 10
distinct groups. Double digestions using the restriction endonucleases
Kpn I and Sac I led to maximum isolate differentiation,
producing unique patterns for 16 isolates and subdividing the remainder
into four groups of two or three isolates. This indicates
the potential of mtDNA RFLP analysis as an excellent tool for fingerprinting
M. anisopliae isolates and for studying genetic polymorphism.