松褐天牛是松材线虫病的最主要传播媒介。白僵菌可通过体壁侵染方式感染松褐天牛，但防治效果不稳定，致死时间长，限制了其推广应用。申请人前期分离到一株可经消化道侵染松褐天牛的球孢白僵菌，同时发现松褐天牛肠道细菌可以影响该菌株侵染效果，并从肠道内分离到一株球孢白僵菌拮抗细菌--成团泛菌Pantoea agglomerans MG2，表明肠道细菌在昆虫防御病原菌侵染中发挥着重要作用，但具体作用机制尚不明确。为明确肠道细菌在抵御球孢白僵菌侵染中作用，本研究拟将P. agglomerans MG2重新接种到松褐天牛体内，采用电镜观察结合实时荧光定量PCR，原位研究P. agglomerans MG2对球孢白僵菌侵染松褐天牛的影响，并纯化鉴定其产生的主要抑菌物质。本项目的开展将有助于阐明肠道细菌在协助宿主抵御病原菌侵染中的作用，同时也为开发具有体壁和消化道双侵染途径的球孢白僵菌新制剂奠定理论基础。

The Japanese pine sawyer, Monochamus alternatus, plays an important role in dissemination of the pinewood nematode, Bursaphelenchus xylophilus. Beauveria bassiana is able to penetrate the host integument and is used as a biocontrol agent to control M. alternatus. However, low killing speed and sensitivity to adverse environment factors limit the widespread use of the B. bassiana. In our prophase research, a B. bassiana strain CZB-02 had been isolated from the dead adult M. alternatus. The strain CZB-02 can infect the M. alternatus through oral feeding. The study also found that the gut bacterium Pantoea agglomerans MG2 can influence the infection process of B. bassiana, but what role does the gut microbiota play in the infection remains unclear. In this propose, the bacterial suspensions of P. agglomerans MG2 were prepared and fed to the larvae of M. alternatus. Then, the effect of live bacteria on colonisation resistance was assessed by light and electron microscopic observations as well as qPCR, and the antifungal compounds from P. agglomerans MG2 were also identified. In some extent, those study will not only expound the immune mechanisms of gut microbiota-host interactions defense against fungal infections, but also would facilitate engineering and improving the virulence of mycoinsecticides through genetic modification.