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 × 10spores·ml in 7 days post inoculation, respectively. Out of these, five (18.5%) isolates scored above 90% mortality on both instar larvae with LT value of 3.33 to 5.33 days at the lowest (10 spores·ml) and 1.93 to 3.17 days at highest (10 spores·ml) spore concentrations and has LC value of 1.5 × 10 to 1.1× 10 spores·ml. Moreover, isolates exhibited the promising mortality better (1.5 × 10 to 3.5 × 10 spores·ml), 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.