Objective To study the function of cytochrome P450 33D3 (cyp-33D3) gene in Bursaphelenchus xylophilus in order to further reveal the molecular pathogenesis mechanism of B. xylophilus, and provide useful information for its biological control.

Method Double strand RNA (dsRNA) interference was used to investigate the effect of silencing of cyp-33D3 on feeding speed, individual size, number of eggs, hatching rate and pathogenicity of B. xylophilus.

Result It was found that the feeding speed of B. xylophilus under ddH₂O and gfp dsRNA treatments were faster than that under cyp-33D3dsRNA interference treatment in the first 5 days. Almost all the hyphae of Botrytis cinerea were consumed by B. xylophilus soaked under ddH2O and gfp dsRNA treatments. In contrast, a large portion of the hyphae still existed under cyp-33D3 dsRNA treatment. No significant effect was found on the individual size of B. xylophilus when cyp-33D3 gene was interfered by dsRNA (P > 0.05). Compared to ddH₂O and gfp dsRNA treatments, the average number of eggs per female decreased 12 and 11 under cyp-33D3 treatment, and the hatching rate of eggs decreased by 46% and 43%, respectively. 40 days after the soaked B. xylophilus were inoculated in Pinus thunbergii seedlings, the pathogenicity of B. xylophilus under ddH₂O and cyp-33D3 treatments were 100% and 43.1%, respectively, while the P. thunbergii seedlings inoculated with B. xylophilus under gfp dsRNA treatment still grew well.

Conclusion The RNA interference of cyp-33D3 gene decreases the feeding speed, the number of eggs, hatching rate and pathogenicity of B. xylophilus. However, RNA interference of cyp-33D3 gene exhibits no significant effect on individual size of B. xylophilus.