Mycobiota of Pinus pinaster associated with Pine Wilt Disease

Abstract

Pine wilt disease (PWD), one of the most threatening diseases to coniferous forests worldwide, results from the complex interaction between the causal agent, the pinewood nematode (PWN) Bursaphelenchus xylophilus, the insect-vector belonging to the genus Monochamus and the Pinus spp. tree host. In the later stages of PWD, PWN undertakes an obligatory mycetophagous phase, feeding on the fungi that colonize the declining trees. Limited studies available indicate that the fungi dominating dead pines, in particular blue-stain fungi assigned to the order Ophiostomatales, may mediate the development and the population of PWN carried by the insect vector. Our aim is to identify and characterise the culturable fungal community of Pinus pinaster putatively associated with the PWN lifecycle. A total of 109 fungal isolates were obtained from symptomatic and asymptomatic P. pinaster collected in a PWD-affected area in Seia (northwest of Portugal) from which representative isolates of each putative species were characterized on the basis of morphology and selected molecular markers (e.g. internal transcribed spacer, ITS; partial b-tubulin gene, tub; and translation elongation factor 1-alpha gene, tef) for phylogenetic inference. Our preliminary data show that fungal communities of symptomatic P. pinaster are less biodiverse and dominated by Ophiostomatales in contrast with the communities of asymptomatic P. pinaster trees. Exploring the diversity of multispecies interactions in PWD provides valuable insights into the successful invasion and adaptation of PWN. This work was conducted as part of the national project PineEnemy: Exploring the NEmatode-MYcobiota interactions in Pine Wilt Disease (LISBOA-01-0145-FEDER-028724) which focus on the characterisation of the structure and dynamics of the nematode-fungi interactions and to which extent can be targeted to disrupt the disease cycle.