AFLP and single-strand conformation polymorphism studies of recombination in the entomopathogenic fungus Nomuraea rileyi.

In most putative asexual fungi analysed through population genetic studies, recombination has been detected. However, the mechanism by which it is achieved is still not known. A parasexual cycle is known to occur in asexual fungi but there is no evidence, as yet, of its prevalence in natural populations. This study was undertaken to investigate the possibility of a parasexual cycle mediating recombination in the mitosporic fungus Nomuraea rileyi. The genotypic diversity in isolates sampled from an epizootic population from South India was studied through AFLP. The AFLP data were subjected to analysis of molecular variance (AMOVA) and cluster analysis. Great genetic variation was observed in the population including the isolates from a single insect. To assess the occurrence of recombination in the population, single-strand conformation polymorphism (SSCP) of partial regions of two mitochondrial (mt) genes (rRNA genes of LSU and SSU) and a nuclear gene (beta tubulin) was performed. The SSCP data were analysed using MP, the tree length permutation test, and multilocus analysis. Recombination was inferred from the SSCP analysis. The occurrence of isolates with diverse genotypes in a single insect; the fact that fungi multiply as hyphal bodies (cell wall-less) in the insect haemolymph; and the inference of recombination in mitochondrial genes (suggesting cytomixis), all indicate that recombination is accomplished by fusion of hyphal bodies of different isolates infecting the insect.