DNA restriction fragment length polymorphisms in the rDNA repeat unit of Entomophaga

Abstract

A heterologous rDNA probe was used to detect restriction fragment length polymorphisms in Entomophaga rDNA sequences. Six Canadian strains of Entomophaga aulicae, isolated from the spruce bud worm or hemlock looper in Ontario or Newfoundland, showed no detectable rDNA variation at 10 different restriction enzyme loci: BamHI, DraI, EcoRI, EcoRV, HindIII, HinfI, MspI, PstI, RsaI, or TaqI. A total of 14 isolates of E. aulicae representative of several different geographic and host origins were compared at the DraI and HindIII rDNA loci and two different banding patterns were detected. Of these, 12 showed the same patterns and were designated E. aulicae type 1. The two members which differed were designated E. aulicae type 2. The variations in rDNA restriction sites did not appear to be geographically dependent. Entomophaga maimaiga, a recently reclassified species from the E. aulicae complex, displayed an rDNA banding pattern clearly distinguishable from the E. aulicae patterns with DraI, EcoRI, EcoRV, or HindIII. Members of the E. grylli species complex exhibited patterns which clearly differed from the patterns seen with either E. aulicae or E. maimaiga isolates. However, members of the E. grylli species complex appeared to be more heterogeneous than those in the E. aulicae complex. Among four E. grylli members, three different rDNA banding patterns were detected with either HindIII or DraI. These were designated as E. grylli type 1, type 2, and type 3. An undesignated Entomophaga isolate from a dipteran host displayed rDNA polymorphisms not previously noted in either the lepidopteran or orthopteran isolates. Our results suggest that RFLPs in rDNA are useful in the delineation of genera and species within the Entomophthorales, but may not be as useful at lower taxonomic levels. These and other RFLPs can however provide useful information regarding the epidemiology of Entomophaga epizootics.