Virulence Change of Beauveria bassiana Strains with Different and the Same Esterase Types after Host Transfer
Virulence of 16 Beauveria bassiana strains belonging to 12 esterase types on the pine caterpillar was tested in a bioassay.The result showed that virulence of strains in different esterase types differed significantly with LT_(50) difference up to several times.The virulence of strains in the same esterase type also changed obviously after host transfer. The virulence of 2 strains, MGS980404-21 of esterase type 05 and MGS980510-06 of esterase type 06, and artificially released Bb13 of esterase type 02 were high,while the the virulence of another strain,MGS980507-34 of esterase type 02,isolated from the grey pine weevil,Brachyderes incanus was low, but it was a prevailing strain in the pine ecosystem.The above results provide evidence for understanding survival of B.bassiana in forest, especially long-term persistence when the pine caterpillar population was at very low level,as well as for sieving of virulent strains.