Study On Screening Superior Strain Of Beauveria Bassiana To Monochamus Alternatus And Exploring The Mechanism Diffused Voluntarily By Scleroderma Sichuanensis Xiao

Pine Wilt Disease (Bursaphelenchus xylophilus Nickle 1970) is a worldwide dangerous disease. In our country,this disease mainly spreads while the Monochamus alternatus's adult supplementing nutrition and laying eggs after emerged, so controlling the Monochamus alternatus effectively is one of the key measures of preventing and curing this disease. Study at home and abroad indicates that utilizing Beauveria bassiana to prevent and cure Monochamus alternatus is an important way to control Bursaphelenchus xylophilus. In this experiment,biological characteristic and malicious strength index of 21 Beauveria bassiana strains have been studied and compared; the experiment of utilizing Beauveria bassiana carried by Scleroderma sichuanensis Xiao to infect Monochamus alternatus larva voluntarily have been explored; the genetic polymorphism of Beauveria bassiana to Monochamus alternatus have been analysed.The results are as follows:1. A comprehensivly comparative study on 21 Beauveria bassiana strains has been made on their virulence to larva of M. alternatus as well as biological characteristics such as spore morphology, vegetative growth, initiation and ability of spore production, germination of spores, and spores' resistance to heat and ultraviolet rays. The strains are arranged in order in terms of biological characteristics as follows: B_xs ,B₅, F-263, B₁, B₆, B_f, B_y2, B₁₂,B_z, B₉, B₃, B₁₄, B₂, B₄, B₈, B₁₃, B_y7, B₁₁, B₁₀, B₇, B₁₅; through comparing the mortality and muscardine rate to Monochamus alternatus larva of 21 strains, it is found that B₅,B_xs and F-263 are superior to other strains. Assessed in terms of biological characteristics and virulence, it is finally found out that the most superior strains of Beauveria bassiana to Monochamus alternatus are B_xs which comes from XiangShan County of ZheJiang province and B5 which comes from JiangSu province.2. The indoor experiment shows, it is feasible to utilize Beauveria bassiana carried by Scleroderma sichuanensis Xiao to infect Monochamus alternatus larva voluntarily. The Beauveria bassiana has a little effect on vigor of Scleroderma sichuanensis Xiao,in virtue of Scleroderma sichuanensis Xiao's ability of initiative searching,Beauveria bassiana is apt to break the ecological line of defence and reach the surface of larva body.3. DNA amplified fingerprints of 21 parasitic Beauveria bassiana from Monochamusalternatus strains from different sources have been tested by means of RAPD technique.30 primers have been selected from 200 primers for RAPD analysis of 21 strains. Altogether 327 scorable DNA fragments have been recorded,with 10.9 RAPD fragments amplified each primer on the average.256 are polymorphic, accounted for 78.3%.Distinct genetic diversity among 21 strains of parasitic Beauveria bassiana from Monochamus alternatus have been found. The clustering results show that 21 strains can be divided into two groups, Cl) Bi> B14-. B4-. 1&5> D6> B7N B^ Bj2n B^ Bio-. F-263-. BXs-> B2-. Bn-. Bf-. Bz-, B9; (2) B3^ Bi5> By2% By7. DNA polymorphism of Beauveria bassiana is correlated with geographic origins,but not with the virulence to Monochamus alternatus larvae.