Effects of Pine Wilt Disease on Rhizosphere Microbiota and Fine Root Fungi: Insights into Enzyme Activity, Ectomycorrhizal Infection and Microbial Composition

Pine wilt disease (PWD), caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus, poses a severe threat to pine forests worldwide. However, the understanding of the impact of PWD on the host microbiome remains limited. This study aimed to investigate the structure and function of the fungal community associated with Pinus thunbergii fine roots and the rhizosphere fungi and bacteria of the tree naturally infected by PWN and the healthy tree. We employed high-throughput sequencing in conjunction with functional prediction tools (Functional Annotation of Prokaryotic Taxa and Fungi Functional Guild) and soil enzyme activity measurements between the two treatments (disease vs. health). The results showed that PWD significantly decreased the activity of beta-cellobiosidase (CEL) and beta-glucosidase (GLS) enzymes involved in carbon cycling in the rhizosphere (p < 0.05). However, PWD did not alter the diversity of rhizosphere bacteria and fine root fungi, but it did cause a significant decrease in the richness of rhizosphere fungi (p < 0.05). Moreover, PWD significantly reduced the abundance of Actinobacteria and genus Gaiella (p < 0.05). Functionally, bacterial intracellular parasites exhibited a higher abundance in the rhizosphere after PWN infection, whereas ureolysis showed a lower abundance (p < 0.05). Fungal saprotroph-symbiotroph exhibited a higher abundance in the rhizosphere after PWN infection, whereas symbiotroph showed a lower abundance (p < 0.05). Additionally, it led to a significant reduction in the infection rate of ectomycorrhizal fungi (p < 0.05). Infected host fine root exhibited higher abundance of pathotroph-symbiotroph, whereas symbiotroph had a lower abundance (p < 0.05). These findings provided valuable insights into the interactions between pine wilt disease, plant microbial communities, and soil enzyme activity.

Automated summary

This study investigated the impact of pine wilt disease (PWD) on the fungal and bacterial communities associated with pine roots and the rhizosphere, as well as soil enzyme activity. The results showed that PWD significantly reduced the activity of carbon cycling enzymes in the rhizosphere. It did not alter the diversity of rhizosphere bacteria and fine root fungi, but it did decrease the richness of rhizosphere fungi. Additionally, PWD led to changes in the abundance of specific bacteria and fungi, as well as a reduction in the infection rate of ectomycorrhizal fungi.