Abstract: To elucidate the molecular mechanisms underlying the differential responses of resistant and tolerant Pinus massoniana phenotypes to pine wilt disease(PWD),tolerant(TC),resistant(RC)and susceptible(NC)phenotypes were artificially inoculated with Bursaphelenchus xylophilus.Phenotypic differences among the phenotypes were compared,and transcriptome sequencing analysis was performed.The results showed that compared with NC,RC exhibited a significantly reduced mortality rate(P<0.01)and a significantly lower pine wood nematode(PWN)load(P<0.01).TC also showed a significantly reduced mortality rate(P<0.01)but had a significantly higher PWN load(P<0.01).Transcriptome analysis revealed that,compared with NC,differentially expressed genes(DEGs)in TC were mainly enriched in pathways such as glutathione metabolism and diterpenoid biosynthesis.In contrast,DEGs in RC were primarily enriched in pathways related to cysteine and methionine metabolism and amino acid biosynthesis.These results suggest fundamental differences between TC and RC in metabolic regulation,energy metabolism,and defense-related metabolic pathways.In conclusion,the resistance and tolerance of P.massoniana to PWD depend on distinct molecular mechanisms:resistant phenotypes directly inhibit nematode proliferation through pathways such as fatty acid metabolism and terpenoid biosynthesis;tolerant phenotypes,on the other hand,mainly survive under high nematode load by strengthening antioxidant pathways such as glutathione metabolism to mitigate oxidative damage.This study provides a molecular basis for developing differential resistance breeding strategies for the prevention and control of pine wilt disease.