Fast recognition of Lecanicillium spp. and its virulence against Frankliniella occidentalis

Abstract Background: Frankliniella occidentalis (Thysanoptera: Thripidae) is a highly destructive sucking pest of numerous crops. The entomogenous fungi of Lecanicillium spp. are important pathogens of insect pests, and some have been developed as commercial biopesticides. In order to explore the wild resources of Lecanicillium spp. in the development of more effective F. occidentalis controls, efficient gene combinations for strain identification were screened from internal transcribed spacer (ITS) and the genes SSU, LSU, TEF, RPB1, and RPB2.Results: In this study, six genes were used to reconstruct the phylogeny of Lecanicillium genus respectively. Among these, only four events (ITS, TEF, RPB1, RPB2) were validated using the gold standard for identifying the strains. All the phylogenetic trees reconstruct by free combination of these four events exhibited the same topology. Bioassay studies of a purified conidial suspension further confirmed the infection of second-instar nymphs and adult female F. occidentalis by seven strains of Lecanicillium. L. attenuatum strains GZUIFR-lun1405 was the most virulent, approximately 8.33% of adult and 23.33% of nymphs F. occidentalis survived after a 7-d exposure. Two strains were selected to compare the effects on the amount of eggs laid by F. occidentalis. The number of nymphs of F. occidentalis significantly decreased when adult F. occidentalis were treated with L. cauligalbarum strain GZUIFR-ZHJ01 compared to the controls.Conclusions: We found that combination of ITS and TEF could be used for fast recognition of Lecanicillium spp. We demonstrated that L. attenuatum, L. cauligalbarum, L araneogenum, and L. aphanocladii had various efficacies against F. occidentalis which were the first to demonstrate efficient control of F. occidentalis. In addition, the L. cauligalbarum strain GZUIFR-ZHJ01 not only caused high mortality in F. occidentalis but also inhibited the fecundity of the pest.