Distinct biogeographic patterns for bacteria and fungi in association with Bursaphelenchus xylophilus nematodes and infested pinewood.

Pinewood nematodes (PWN, Bursaphelenchus xylophilus ) are destructive plant parasitic nematodes that cause pine wilt disease (PWD) by attacking the vascular systems of pine trees, resulting in widespread tree mortality. Research has shown that there are connections between nematode-associated microbes and PWD. Yet the variations in microbial communities across different geographic regions are not well-understood. In this study, we examined the bacterial and fungal communities associated with nematodes and infested wood collected from 34 sites across three vegetation zones in China, as well as samples from the United States, using 16S rRNA and internal transcribed spacer (ITS) gene amplicon sequencing. The predominant genera Pseudomonas and Rhodococcus were found in nematodes, and Acinetobacter was present in the wood of PWD-infected pine trees across China. Network analysis revealed that core bacterial taxa belonged to the Pseudomonadota and Actinomycetota phyla for the nematodes, whereas the Pseudomonadota and Bacteroidota phyla were dominant in the infested wood. Identification of enriched key microbial taxa in nematodes and infested wood across vegetation zones indicates distinct biogeographic microbial community structures and key bacterial species. Although the nematode-associated bacterial community showed consistency across geographic distances, the similarity of the PWD pine trees' bacterial community decreased with distance, suggesting a spatial correlation with environmental variables. Our findings enhance our understanding of the microbiota associated with pinewood nematode (PWN) and offer valuable insights into PWD management.
Importance: Our research uncovered specific bacteria and fungi linked to pinewood nematode (PWN) and infested wood in three different vegetation zones in China, as well as samples from the United States. This sheds light on the critical roles of certain microbial groups, such as Pseudomonas, Acinetobacter , and Stenotrophomonas , in influencing PWN fitness. Understanding these patterns provides valuable insights into the dynamics of PWN-associated microbiomes, offering potential strategies for managing pine wilt disease (PWD). We found significant correlations between geographic distance and similarity in bacterial communities in the infested wood, indicating a spatial influence on wood-associated microbial communities due to limited dispersal and localized environmental conditions. Further investigations of these spatial patterns and driving forces are crucial for understanding the ecological processes that shape microbial communities in complex ecosystems and, ultimately, for mitigating the transmission of PWN in forests.
Competing Interests: The authors declare no conflict of interest.