The Occurrence of Pine Wilt Disease Caused by Bursaphelenchus xylophilus Related to Endophyte

Pine wilt disease caused by pine wood nematodes (PWN), Bursaphelenchus xylophilus, was one of main forestry diseases. Its exact pathogenic mechanism was not well-known. An endophyte bacterium, which was isolated from both diseased trees infected with this disease and healthy trees of masson pine, Pinus massoniana, was identified as Bacillus spp. Both bacterium and its metabolite were pathogenic to pine seedlings without roots and twigs, and symptom caused by them was alike to that of this disease, but they had no effect on healthy seedlings. It suggested that the occurrence of this disease related to this endophyte bacterium and it was weak pathogen. Pine twigs inoculated with PWN were cultured in 1.0 mmol/L benzoic acid (BA) solution and tap water, respectively. The results showed that the development of wilt disease of twigs cultured in BA solution was restrained, although PWN in these twigs increased as normally as those in twigs cultured in tap water. It suggested that endophyte of pine tree would be the main pathogenic factor of the disease, and PWN was one of irritative factors.