Abstract: The northward expansion of Bursaphelenchus xylophilus has caused devastating disasters in the northeastern region, posing a significant threat to Pinus koraiensis, which is the major component species of the top ecological community of the Northeast China forest area.This study aims to enrich the molecular mechanism of the interaction between P.koraiensis and B.xylophilus, thus laying a theoretical foundation for the breeding of disease-tolerant P.koraiensis.The disease tolerance of 20 families of P.koraiensis to B.xylophilus was identified by artificial inoculation and different families of P.koraiensis were divided into three categories: tolerant, susceptible and high-susceptible.The RNA of tolerant and high-susceptible P.koraiensis was extracted for transcriptome sequencing.The α-terpineol synthase gene（Pk-αts） related to disease tolerance was screened and cloned.The expression level of Pk-αts in 4 tolerant, 2 susceptible, and 4 high-susceptible P.koraiensis was randomly detected by RT-qPCR, and the relative tolerance index of these 10 P.koraiensis families was calculated.The correlation between Pk-αts expression level and the relative tolerance index of P.koraiensis was analyzed.The results showed that after inoculating B.xylophilus for 20 days, only a few needles of tolerant P.koraiensis turned yellow, with an average relative tolerance index of 0.88, while high-susceptible P.koraiensis showed partial needle redness, with an average relative tolerance index of 0.09.Transcriptome sequencing identified 1 770 genes that were up-regulated in tolerant P.ko-r aiensis and had no change or down-regulated in high-susceptible P.koraiensis.The relative expression of Pk-αts in tolerant P.ko-r aiensis was 2.83, which was extremely significant, but the relative expression in high-susceptible P.koraiensis was-1.27.The cloned Pk-αts gene was 1 230 bp in length, encoding a protein composed of 409 amino acids, with an isoelectric point of 5.55 and a relative molecular weight of 47.60 ku.After comparison, it had the highest homology with the α-terpineol synthase gene and contained conserved motifs such as DDxx D and RRx8W of plant monoterpene synthases and Terpene＿synth domain, which were consistent with the structural characteristics of monoterpene synthases.RT-q PCR detection showed that the expression of the Pk-αts gene was upregulated（the average expression level is 1.39） in tolerant P.koraiensis, while it was unchanged or downregulated in susceptible and high-susceptible P.koraiensis, indicating that the upregulation of the Pk-αts gene expression was synchronized with the temporal and spatial of P.koraiensis tolerance to in the early stage of B.xylophilus infection.The expression level of Pk-αts was positively correlated with the relative tolerance index of P.koraiensis（Pearson’s coefficient was 0.911, P＜0.01）, indicating that the up-regulated expression of the Pk-αts gene improved the disease tolerance of P.koraiensis.In summary, different families of P.koraiensis have different tolerance to B.xylophilus, and some P.koraiensis have certain disease tolerance.The up-regulated expression of Pk-αts gene alleviates disease symptoms and helps to improve the disease tolerance of P.koraiensis to B.xylophilus.The Pk-αts gene can be used as a detection target for identifying tolerance of P.koraiensis to B.xylophilus, which is helpful for the breeding of tolerant P.koraiensis.