Molecular phylogeny and pathogenicity of indigenous Beauveria bassiana against the tomato leafminer, Tuta absoluta Meyrick 1917 (Lepidoptera: Gelechiidae), in Ethiopia

Background Tuta absoluta Meyrick 1917 (Lepidoptera: Gelechiidae) is an invasive, pesticide resistant, and a major treat of tomato production in the world. It needs effective management options that naturally infect the insect without causing any identified side effects. Entomopathogenic fungi (EPF) are the most important options. However, geographic origin and climatic condition apparently creates genetic variation among EPF strains that influence on their pathogenicity. Thus, screening of effective EPF strains from the local source is vital to develop environmental friendly pest control tactic for T. absoluta. Results In this study, 27 indigenous Beauveria were isolated from the various types of soil and 12 of the isolates were screened based on their biological efficiency index (BEI). These isolates scored 65.7-95.7% and 68.3-95% of mortality against second and third instar larvae of T. absoluta at concentration of 1 x 10(7)spores center dot ml(-1) in 7 days post inoculation, respectively. Out of these, five (18.5%) isolates scored above 90% mortality on both instar larvae with LT50 value of 3.33 to 5.33 days at the lowest (10(4) spores center dot ml(-1)) and 1.93 to 3.17 days at highest (10(8) spores center dot ml(-1)) spore concentrations and has LC50 value of 1.5 x 10(3) to 1.1x 10(5) spores center dot ml(-1). Moreover, isolates exhibited the promising mortality better (1.5 x 10(6) to 3.5 x 10(7) spores center dot ml(-1)), sporulated over the larval cadavers, well grown at optimal temperature, and produced chitinolytic enzymes. Molecular analysis showed that isolates have nearly monophyletic characters and grouped under species of Beauveria bassiana. Conclusion Different types of soil in Ethiopia are an important source of B. bassiana, and these isolates showed promising pathogenicity against T. absoluta, which is crucial for ecofriendly biopesticide development. Although isolates were nearly monophyletic in phylogenetic study, five of them were highly effective in the laboratory bioassays against T. absoluta; however, further field evaluation is required for mass production.

Automated summary

The study isolated 27 indigenous Beauveria strains from different types of soil in Ethiopia, with 12 of them screened based on their biological efficiency index (BEI). These isolates showed promising pathogenicity against Tuta absoluta, with five of them highly effective in laboratory bioassays and nearly monophyletic characters. Further field evaluation is needed for mass production.