Screening for high virulence strains of Metarhizium anisopliae and yield determination of its extracellular protease

The virulence of different Metarhizium anisopliae,which screened from orchards soil,was evaluated by using the larvae of Galleria mellonella L.as the test insect in laboratory.Four high virulence strains of M.anisopliae were obtained,the LT50 values were between 1.85 d and 2.56 d.The LD50 values were between 6.11×102 and 1.55×104 spores.Gelatin-AGAR analysis method was used to determine the extracellular protease enzyme levels of the high virulence strains of M.anisopliae.The results showed that the production of extracellular protease among high virulence strains was different,and there was an obvious liner correlation between extracellular protease level and pathogenicity to larvae of G.mellonella.