endophyte metagenome Metagenome

Pine wilt disease (PWD) is a devastating forest disease present worldwide. In this study we analyzed the effects of the invasion of Bursaphelenchus xylophilus, the major pathogen causing PWD, on the endophytic microbiome of adult P. pinaster trees. Wood samples from trees with different degrees of PWD disease were collected at Arganil (site M) and Oliveira do Hospital (site A), Portugal. Endophytic bacteria were characterized by DGGE fingerprinting and barcoding. Endophytic microbiome from P. pinaster trees differed significantly between the two sampling locations, indicating site specific adaptation but consequences of the invasion with the pathogen were comparable. Main bacterial OTUs belonged to the Proteobacteria (39% (site M) - 97% (site A)), and Firmicutes (0.70% (site A) - 44% (site M)). Bacterial communities showed to be more divergent in trees of the medium symptom stage (sIII) and more diverse in the most affected trees (sV). Results suggest, that in the first stages of the disease, the immune system of the plants is repressed by the pathogen, resulting in a colonization of the wood interior by soil microorganisms. These microbes promote degradation of plant compounds, additional weakening and an uncontrolled bacterial colonization.