Thermal tolerance of Cameroonian fungal isolates

Biology and virulence of entomopathogens are known to be affected by environmental conditions. In this study aiming to select thermo-tolerant isolates for biopesticides development against Cosmopolites sordidus, germination, mycelia growth and sporulation of six local Cameroonian isolates of two promising microbial agents Beauveria bassiana and Metarhizium anisopliae were assessed under seven different thermal conditions (13, 15, 20, 25, 29 33 and 37 °C). The Transmission potential was also determined at 25 ± 1 °C by dipping adult weevil of four vectors ratios (0, 10, 30 and 50 %) with conidial suspensions labelled 3.2 x108 conidia/ml. Incubation temperature and isolates affected significantly germination, mycelia growth and conidia production. All isolates had large thermal tolerance ranges (13–33 °C) except MIITAC6.4.2 (20-29 °C) which had the narrowest range. Horizontal transmission resulted in mortality of non-inoculated weevils from 4.63 ± 1.77 to 53.3 ± 11.9 %. . The isolate BIITAC6.2.2 exhibited high auto-dissemination potential and high conidia yield in cadavers. This results demonstrate the potential use of these isolates for biopesticides development against C. sordidus in Central Africa.