Cedar Natural Conditions In China, The Mechanism Of Pine Wilt Disease-free

The pine wilt disease caused by the pine wood nematode, Bursaphelenchus xylophilus (Steiner& Buhrer) Nickle, was the most devastating diseases of pine trees, which was found firstly in 1982 in China and caused a large lost of pine trees. In china, Pinus thunbergii and P.massoniana were easyly infected by pine wood nematode, however the infection to Cedrus deodara is unknown. Some studies had shown that the pine wood nematode,Bursaphelenchus xylophilus had Pathogenicity to Cedrus deodara in USA and Japan, but Pathogenicity to the pine was limited in China.,in deed there are no direct proof that the nematode could infect in China. In order to tackle out the trouble problem, we inoculated Pinus thunbergii and Cedrus deodara with pine menatodes collected from China and Japan respectively and studied the pathogenicity of them. The main results were as follows:1. The black pine died totally after inoculation with two kinds of nematodes, respectively, however the pine of Cedrus deodara inoculated with Japanese nematode died 50% and the pine still kept healthy after inoculated with nematode from Zhe Jiang in China.2. A large number of nematodes were islolated from dead tress after inoculation. Meanwhile, nematodes were found in living tress, which were infected. However,the trees of Cedrus deodara were inoculated with nematodes kept living, though some nematodes were found in them.3. 72h later, the dparenchymatous and resinosis cell of pine trees, including Pinus thunbergii, P.massoniana had been injured after inoculated with both kinds of nematodes, respectively and both cells of radialxyle and resin duct were hurt. 144h later, the cells of pines were all destroyed. The dparenchymatous and resinosis cells of Cedrus deodara inoculated with Japanese nematode were damaged, however the cells of pine trees inoculated with Chinese nematode were hurt slightly.4.Bactrial strains of G and H were isolated from Japanese nematode and strain of K was isolated from Chinese nematode.5.in vitro, Bactrial strain s of G and H had strong toxicity to Pinus massoniana. Bactrial strain s of G had strong toxicity to Cedrus deodara,however Bactrial strain s of k had no toxicity to Cedrus deodara.The above results showed that the reason for Cedrus deodara non-infected by B. xylophilus was the variation happened for the changes of bacterium species on the pine nematode after them were introduced into China.