Biodiversity and virulence characterization of entomopathogenic fungi isolated from soils in different regions of Nigeria

Background Studying the diversity of the indigenous entomopathogenic fungi (EPF) is a prerequisite to effective insect pest control. The distribution and occurrence of EPF from the soil across Nigeria were evaluated. Three subsoil samples from three locations in each of the 11 states were used to isolate the fungi by the insect bait method. Three fungal rates, 1.0 x 10(2), 5.0 x 10(1) and 7.5 x 10(1) spores/ml, were applied to the Galleria larvae. Results EPF occurred in 41.1% of the soil sampled. These fungi belong to five and an unidentified genus. High species diversity was observed in Abuja with 6 species, and a uniform diversity of 5 species in Gombe, Ibadan, Jos, Kano, Lagos, Nasarawa and Port Harcourt. The Shannon-Wiener index ranges from 2.48 to 1.84. Similarly, species evenness showed a distinct similarity across the 11 sampling states and ranges from 0.99 to 0.92. Simpson Diversity Index was found to be highest in Bauchi with 0.31 and lowest in Abuja with 0.19. The mortality of the Galleria mellonella (L.) larvae differed significantly (P < 0.01) with EPF species and time of exposure. There was also a strong (P < 0.001) relationship between larval mortality and conidial concentration within and among the species. The virulence of the isolated fungi on Galleria mellonella larvae based on LC50 differs with states (sampling site) even within the same species. Conclusions The present study uncovered the diversity and occurrence of EPF in soil across Nigeria. In addition, the results can be useful in selecting the suitable soils and best adapted EPF in a particular soil across the study area, or it could be the beginning of a molecular study.