Phylogenetic Analysis of Caterpillar Fungi by Comparing ITS 1-5.8S-ITS 2 Ribosomal DNA Sequences

ABSTRACT

This study was carried out to identify the phylogenetic relationships among several caterpillar fungi by comparing the sequences of internal transcribed spacer regions (ITS1 and ITS2) and 5.8S ribosomal DNA (rDNA) repeat unit. The sequences of ITS1, ITS2, and the 5.8S rDNA from 10 strains of Cordyceps species, 12 strains of Paecilomyces, 3 strains of Beauveria, 2 strains of Metarhizium and 1 strains of Hirsutella were amplified, determined and compared with the previously known Cordyceps species. The sequences of 5.8S rDNA were more conserved in length and variation than those of ITS regions. Although the variable ITS sequences were often ambiguously aligned, the conserved sites could be found. In the phylogenetic tree, the species generally divided into three clusters, supported by their morphology and/or host ranges. The 5.8S rDNA and ITS1 sequences among 10 species of Cordyceps militaris were identical and only one base pair in ITS2 sequence was different. Cordyceps sinensis and Cordyceps ophioglossoides were also clearly different, although they belonged to the same cluster. The GenBank database search of species revealed sister taxa of an entomogenous fungus. Metarhizium was used as an outgroup in all taxa.