Diversity analysis of Beauveria bassiana isolated from infected silkworm in southwest China based on molecular data and morphological features of colony.

Beauveria bassiana is an important entomopathogenic fungus that not only often causes infection and epidemics of wild insects but some strains also show pathogenicity to the silkworm, Bombyx mori. The present study is about diversity of B. bassiana isolated from the silkworm in southwest China. Five strains of B. bassiana were isolated from infected silkworm. Two isolates, GXtr1009 and GXtr1010, were isolated from infected silkworms treated with two kinds of biological pesticides applied in Guangxi province, and three isolates, SCsk1006, YNsk1106 and GXsk1011, were collected from naturally infected silkworms from different geographical locations in Yunnan and Sichuan. All of the isolates showed highly similar conidia and conidial fructification, but the colony characteristics demonstrated great differences among the isolates. The ITS and 18S rDNA sequence analysis was sufficient to identify all five isolates as B. bassiana. However, the dendrogram, based on the ISSR data, produced two large genetic groups. GXtr1009 and GXtr1010 comprised one group, and SCsk1006, YNsk1106 and GXsk1011 converged in a different large group. The results suggested that, although all of these five B. bassiana strains were pathogenic to silkworms, strains of biological pesticides could be differentiated from strains of naturally infected silkworm via ISSR analysis.