Morphological and molecular identification of the entomopathogenic fungus Purpureocillium lilacinum and its virulence against Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) larvae and pupae

Abstract

Background

The tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a serious pest of solanaceous plant species, mainly Solanum lycopersicum L. The entomopathogenic fungi, an alternative to chemical insecticides, proved to be an efficient biocontrol agent in reducing pest population density. In the present study, an entomopathogenic fungus, Purpureocillium lilacinum isolated from soil was identified based on the morphological and molecular characteristics and its pathogenicity was tested against target pest.

Results

The micromorphological characters showed variations in growth pattern, shape and colour on different cultural media. For molecular analysis, a phylogenetic tree based on ITS/LSU and ITS/β-tubulin (benA) gene regions was constructed which revealed the isolate (FC18) as P. lilacinum (Thom) Luangsa-ard, Houbraken, Hywel-Jones and Samson (Family: Ophiocordycipitaceae). Further, the pathogenicity of P. lilacinum was tested using different spore concentrations (1 × 10⁸, 1 × 10⁷, 1 × 10⁶, 1 × 10⁵ and 1 × 10⁴ spores/ml) on larval and pupal stages of T. absoluta, which showed a dose-dependent mortality. At the highest concentration (1 × 10⁸ spores/ml), the mean mortality of 92.99, 83.05, 72.0% of second, third and fourth instar was observed, respectively. Pupal mortality also showed significant differences at different spore concentrations.

Conclusion

Obtained results showed that the virulence of the indigenous strain of P. lilacinum on T. absoluta can be utilized in the field suppression of the pest as a potent biocontrol agent.