Pine wilt disease (PWD) is one of the most devastating diseases of Pinu s spp. And is caused by the pine wood nematode (PWN), Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle. To study adaptation of PWN to survive in hosts that differ in resistance, we examined the self-regulatory characteristics of PWN at the biological and molecular levels early in the interaction. Two-year-old susceptible Pinus thunbergii and resistant Pinus taeda were selected for this experiment, and changes in PWNs after inoculation were assessed. qRT-PCR was used to detect changes in genes related to PWN pathogenicity and detoxi-fication. The results showed that the migration and reproduc-tive abilities of PWNs in P. thunbergii were stronger than those of PWNs in P. taeda . After 7 d, the number of nema-todes in P. thunbergii was approximately 3.2-fold higher than in P. taeda . After 15 d, the number of nematodes in P. thunbergii was approximately twofold higher than that in P. taeda . Because PWN can adjust its sex ratio after infection,we compared the sex ratio of uninoculated PWNs , to that in the two pine species. In P. thunbergii , the female to male ratio first decreased and then stabilized over time; in P. taeda first decreased and then increased. Relative fat accumula-tion in PWNs increased significantly after the PWNs entered the tree body; the accumulation rate in P. thunbergii was higher than in P. taeda at 7 d, but lower after 15 d. Scan-ning electron microscopy (SEM) showed significantly more bacteria on the surface of PWNs in P. taeda compared with PWNs in susceptible P. thunbergii . At 12 h after inocula-tion, the expression of genes related to cell-wall degrada-tion ( BxBeta1-4 and Bxpel1 ), effectors ( BxCDP1 , BxSapB1 ), and active oxygen metabolism ( Bxy-ctl-1 and BxGST3 ) was 2-6 × higher in the resistant pine than in the susceptible one . In contrast, in PWNs, the expression of autophagy-related genes BxATG1 and BxATG16 was 1.5-2 times higher in P. thunbergii than in P. taeda. These results indicate that the interaction between PWNs and pine trees with differ-ent resistance levels elicits a series of physiological and molecular adaptations that affect nematode reproduction and virulence. This study will help elucidate the adaptive mechanisms of PWN in different pine trees.

Yaqi Feng;Lin Rui;Xinyu Wang;Xiaoqin Wu

Co-Innovation Center for Sustainable Forestry in Southern China,College of Forestry,Nanjing Forestry University, Nanjing 210037,People's Republic of China;Jiangsu Key Laboratory for Prevention and Management of Invasive Species,Nanjing Forestry University, Nanjing 210037,People's Republic of China

林业研究（英文版）

[1]Yaqi Feng;Lin Rui;Xinyu Wang;Xiaoqin Wu-.Adaptation of pine wood nematode, Bursaphelenchus xylophilus , early in its interaction with two Pinus species that differ in resistance)[J].林业研究（英文版）,2022(04):1391-1400

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