High Temperature Tolerance of Conidia from Beauveria spp. and Metarhizium spp. Entomopathogenic Fungi

The conidia of 2 isolates of Beauveria and 3 isolates of Metarhizium were heat treated in water bath and in oven at 35￣100℃ for 10￣60 min. The germination and growth of the conidia was not influenced at 35℃ and the sensitive range of these conidia was at 40￣50℃. The isolate B9 collected from Jilin province in north China, was the most sensitive to high temperature among the 5 isolates, and only 20% of the conidia of this isolate germinated when treated at 40℃ for 10 min. The isolate M189 collected from Africa had an especially high tolerance to temperature. The rate of conidium germination still maintained above 40% at 40℃ for 4 h or at 50℃ for 1 h. About 1% of the conidia could germinate at 60℃ for 20 min. The result of the culture on PPDA(modified PDA) plates showed that the colony forming unit (CFU) of the isolate M189 was 67.7% and the other 4 isolates′ were less than 1% at 35℃.