Genetic diversity of pine‐parasitic nematodesBursaphelenchus xylophilusandBursaphelenchus mucronatusin China

Summary The internal transcribed spacer (ITS) regions ofrDNAhave been routinely employed for identification and phylogenetic analysis of many nematode species. In this study, the intra‐ and interspeciesITSgenetic diversity ofBursaphelenchus xylophilusandBursaphelenchus mucronatuswas evaluated. Ninety‐one isolates of the two nematode species collected from 14 Chinese provinces, Japan and Korea were used forITS‐PCRand sequencing. An unweighted pair group cluster analysis dendrogram clustered them as twoB. mucronatusand oneB. xylophilusindependent clades. Principal component analysis showed the phylogenetic relationship of the two nematode species more clearly;B. mucronatusisolates were separated into more than four groups, whereasB. xylophilusisolates still clustered into a group. The results of the Mantel test indicated the correlation of genetic distance matrices and geographic distance matrices was significant for both nematode species. The genetic differentiation coefficient (Gst) and gene flow (Nm) ofB. mucronatuswere 0.341 and 1.091, respectively, suggesting the importance of landscape heterogeneity and considerable obstacles for genetic exchange amongB. mucronatus isolates in China. However,GstandNmofB. xylophiluswere 0.188 and 2.151, respectively, very different compared toB. mucronatus. This could be owing to the short‐term introduction ofB. xylophilusinto China and a rapid spread through anthropogenic pathways. Our work adds to the understanding of the genetic diversity and genetic relationship of the two pine‐parasitic nematode species, and will aid in controlling them in the future.