First detection of Bursaphelenchus xylophilus associated with Pinus nigra in Portugal and in Europe

Abstract

The pinewood nematode (PWN), Bursaphelenchus xylophilus, is the causal agent of pine wilt disease. This species has been reported from the United States of America and Asia associated with important forestry tree species, including pine, spruce, fir, larch and other conifers. However, in Europe, the devastating epidemics centred in Portugal’s mainland, and the most recent detections in Madeira Island and in Spain were restricted to Pinus pinaster alone. During the 2013 national survey, wilted Pinus nigra trees, from the central region of Portugal, were sampled. A Bursaphelenchus species was found in very high numbers, with an average up to 5000 nematodes per 10 g of wood, collected from different pine trees. Morphological identification of those specimens, including the presence of a bursa in the male tail, four lateral incisures, shape of spicules, presence of a vulva flap and female rounded tail, was in agreement with the PWN description. Species identification was confirmed also using species-specific primers targeting the ITS region of the ribosomal DNA to the PWN. Herein, B. xylophilus is reported for the first time associated with declining P. nigra in Portugal, and in Europe. Simultaneously, the insect vector Monochamus galloprovincialis was also detected colonizing the PWN-infected P. nigra.