Development of external and internal symptoms in pine seedlings (pinus sylvestris) due to inoculation with bursaphelenchus vallesianus

Abstract

Development of needle discoloration and histological symptoms induced by Bursaphelenchus vallesianus were investigated in 3-year-old Pinus sylvestris plants. Seedlings were inoculated with B. vallesianus isolated from declining P. sylvestris in Valais, Switzerland. Plants were grown in the greenhouse at 28°C mean temperature and a low watering regime. The histological symptoms in the inoculated plants appeared as necrosis of parenchyma cells in the cortex, rays and cambium, about two weeks after inoculation. Tissue necrosis expanded to the xylem during the next days followed by the formation of cavitations. The external symptoms appeared as browning of needles on the stem and branches below the inoculation site, followed by wilting of the whole plant. Needle discoloration was delayed by few days to the internal symptoms. Our study with B. vallesianus demonstrated that external and internal symptoms followed a pattern similar to that caused by B. xylophilus and supported the hypothesis that the mechanism causing pine wilting is comparable among the pathogenic Bursaphelenchus species. © 2008 Springer Science+Business Media B.V.