Molecular phylogenetic identification of Metarhizium and Beauveria and their bio-efficacy against chilli thrips, Scirtothrips dorsalis

Molecular phylogenetic species recognition is essential in precisely differentiating the morphologically cryptic species of Metarhizium and Beauveria. These fungal entomopathogens can be an alternative to conventional synthetic insecticides and are emerging as effective biocontrol agents against sucking insect pests. In the present study, we identified Metarhizium and Beauveria species in diverse agricultural and semi-natural ecosystems of south Karnataka State of India using phylogenetic markers and evaluated their pathogenicity against Scirtothrips dorsalis. Based on morphological characters, 34 Metarhizium and 15 Beauveria isolates were identified in agricultural and semi-natural ecosystems. Phylogeny of Metarhizium was resolved using markers, TEF1-α, MzIGS3, and ITS rDNA to two species, M. pingshaense and M. guizhouense and Beauveria was resolved using markers, TEF1-α, Bloc, and ITS rDNA to a single species, B. bassiana based on phylogenetic optimality criteria. Isolates of M. pingshaense and B. bassiana resolved three phylogenetic clades each and M. guizhouense resolved one phylogenetic clade. Phylogenetic clades of M. pingshaense and B. bassiana exhibit intraclade variation and are not associated with crop plant or host insect. Laboratory bio-efficacy studies of 49 isolates of Metarhizium and Beauveria against adult S. dorsalis showed that pathogenicity varied significantly among isolates. Greenhouse bioassays revealed the high virulence of B. bassiana isolates over M. pingshaense isolates against S. dorsalis. Low LC50 value of 2.8 × 104 conidia/ml was obtained for B. bassiana GKVK 01_06 isolate against S. dorsalis. Our results indicate that indigenous B. bassiana isolates have strong potential in the management of S. dorsalis.