Genetic polymorphism of natural isolates of Nosema Pyrausta (Microsporidia: Nosematidae)

Abstract

Background. Microsporidia are ubiquitous parasites of animals, most abundant in arthropods and fishes. Many species of these parasites are important from standpoints of medicine, veterinary and agriculture. Microsporidium Nosema pyrausta is an important disease agent in corn borer populations causing adverse effect on host fitness. Genotyping of this parasite is necessary for proper species identification and intraspecific polymorphysm studies. Materials and Methods. Microsporidia-infected larvae of corn borers of the genus Ostrinia were recovered from Krasnodar Territory in Russia and Gomel Region in Belarus. Small subunit ribosomal RNA (SSU rRNA) was amplified and sequenced directly, while intergenic spacer (IGS) was amplified, cloned and sequenced (1-5 clones per sample) for four isolates of microsporidia. Sequences were aligned and compared using standard bioinformatics tools (Clustal W and BLAST). Results. SSU rRNA genotyping showed allocation of all four isolates to N. pyrausta with 100% identity to each other and 99.7% similarity to Nosema bombycis, the type species of the genus Nosema. High levels of IGS sequence variation (61-74%) is observed both between isolates of different species and populations of microsporidia as well as between molecular clones within parasite isolates from individual hosts. Conclusion. N. pyrausta is widespread in corn borer populations and its genetic structure is complicated, as in other species of these parasites. Further studies of molecular markers are needed for genetic differentiation of geographic isolates of N. pyrausta.