Population structure of Bursaphelenchus xylophilus and its closely related Bursaphelenchus species in Liaoning province

In order to clarify the species and distribution of Bursaphelenchus xylophilus and its related species of Bursaphelenchus in Liaoning Province, and reveal the genetic diversity of Bursaphelenchus with B. xylophilus as the dominant species. Based on the systematic investigation of wilting dead pine samples in 14 cities of Liaoning Province, the identification and genetic structure analysis of Bursaphelenchus were carried out by combining morphometrics and molecular phylogeny. The results showed that: 1) Four species of Bursaphelenchus were identified by morphological and molecular identification, among which B. xylophilus was the dominant species and B. mucronatus was the subdominant species. 2) The sequence homology of rDNA-28S D2-D3 region between the collected nematodes and the corresponding species was as high as 99%, which was consistent with the results of morphological identification. The results of phylogenetic and genetic diversity analysis showed that there was a close genetic relationship among the intraspecific strains of B. xylophilus in Liaoning Province, and the overall genetic diversity was high (H_d=0.9670, P_i=0.01091). 3) There was moderate genetic differentiation among the six geographical populations of B. xylophilus (F_ST=0.21643), and most of the genetic variation was derived from the strains within the geographical population (the variation within the six geographical populations accounted for 78.36%, σ²=3.37912), indicating that there was a multi-source invasion path in Liaoning Province. This study revealed the biodiversity pattern and population genetic structure characteristics of B. xylophilus complex in Liaoning Province, and provided important theoretical basis and data support for the molecular epidemiological traceability and regional precise prevention and control of the disease.