Evolutionary distinction between the geographical isolates of Beauveria bassiana from Iran and their efficacy against Helicoverpa armigera

Beauveria bassiana is a cosmopolitan and soil-borne fungus EPF which is widely used as a biological insecticide. Regarding the remarkable intraspecific variability amongst the B. bassiana isolates, for the first time, the evolutionary distinction between the geographical isolates of entomopathogenic fungi (EPF), Beauveria bassiana, belonging to two distinct geographical areas of Iran have been examined for taxonomic affiliation and their evolutionary distinction to other isolates. In total, 400 soil samples were randomly collected from different cultivated and non-cultivated areas of Khosroshahr and Jiroft region. Insect baiting technique was used to isolate entomopathogenic fungi from the soil. Six well-supported clades within the Beauveria were resolved in the ITS-rDNA phylogenies. Native Beauveria bassiana isolates were determined to be non-monophyletic and consist of three clades named A1, A2, and A3. No correlation was recorded between the geographical origins of the isolates and the topology of the phylogenetic tree. Results suggest that compared to other clades, the members in the clade A1 are representative of a genealogically distinct group of B. bassiana, presumably with higher fitness cause better establishment and persistence in different environments. From both geographical regions, six B. bassiana isolates belonging to phylogenetically distinct clades were subjected to bioassay against the larva of the Helicoverpa armigera as a major pest of cotton in Iran. Although the virulence of the isolates differed significantly, no obvious relationship was detected between the virulence of the isolates and their phylogenetic relatedness. Jiroft isolates showed lower virulence against larvae than did fungi from Khosroshar.