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- Chitosan increases Pinus pinaster tolerance to the pinewood nematode (Bursaphelenchus xylophilus) by promoting plant antioxidative metabolismPublication . Silva, Marta Nunes da; Santos, Carla S.; Cruz, Ana; López-Villamor, Adrián; Vasconcelos, Marta W.The pine wilt disease (PWD), for which no effective treatment is available at the moment, is a constant threat to Pinus spp. plantations worldwide, being responsible for significant economic and environmental losses every year. It has been demonstrated that elicitation with chitosan increases plant tolerance to the pinewood nematode (PWN) Bursaphelenchus xylophilus, the causal agent of the PWD, but the biochemical and genetic aspects underlying this response have not been explored. To understand the influence of chitosan in Pinus pinaster tolerance against PWN, a low-molecular-weight (327 kDa) chitosan was applied to mock- and PWN-inoculated plants. Nematode population, malondialdehyde (MDA), catalase, carotenoids, anthocyanins, phenolic compounds, lignin and gene expression related to oxidative stress (thioredoxin 1, TRX) and plant defence (defensin, DEF, and a-farnesene synthase, AFS), were analysed at 1, 7, 14, 21 and 28 days post-inoculation (dpi). At 28 dpi, PWN-infected plants elicited with chitosan showed a sixfold lower nematode population when compared to non-elicited plants. Higher levels of MDA, catalase, carotenoids, anthocyanins, phenolic compounds, and lignin were detected in chitosan-elicited plants following infection. The expression levels of DEF gene were higher in elicited plants, while TRX and AFS expression was lower, possibly due to the disease containment-effect of chitosan. Combined, we conclude that chitosan induces pine defences against PWD via modulation of metabolic and transcriptomic mechanisms related with plant antioxidant system.
- Risk of damage by the pine weevil Hylobius abietis in southern Europe: effects of silvicultural and landscape factorsPublication . López-Villamor, Adrián; Carreño, Santiago; López-Goldar, Xosé; Suárez-Vidal, Estefanía; Sampedro, Luis; Nordlander, Göran; Bjorklund, Niklas; Zas, RafaelThe pine weevil (Hylobius abietis) is one of the most devastating pests of regenerated coniferous forests in northern and central Europe. Although it is also present and potentially harmful in southern Europe, little attention has been paid to this pest in that region. With the aim of quantifying the potential risk of the pine weevil as a forest pest in southern Europe, we performed an intensive assessment of weevil abundance and damage in 21 Pinus pinaster and P. radiata plantations established in recent coniferous clear-cuts in Galicia (NW Spain), i.e. in the south-western part of the natural distribution of H. abietis. The effect of several silvicultural and landscape factors as modulators of weevil risk was analyzed. Abundance of adult pine weevils was highly variable across the sampling plots, with the number of trapped insects significantly correlated with mean air temperature during each trapping period. Damage rate was, however, fairly constant across the whole study period. No significant relationship between pine weevil abundance and damage was observed. Up to 85% of the planted seedlings were attacked and the mortality rates reached 45% in some plots. No weevil preferences were found between the two pine species. Pine weevil damage was positively related to the amount of slash (logging waste) on the ground and negatively related to the time since clear-felling occurred. Once these factors were accounted for, the abundance of mature coniferous forest in the vicinity (500-2000 m) of the clear-cut significantly and positively affected pine weevil damage. We conclude that a high risk of pine weevil damage does exist in NW Spain. Low-intensity forest management together with the scarcity and discontinuity of mature conifer forest in the region seem to be the reason why this forest pest is largely ignored by forest owners and forest-health services. If the forest sector intensifies in this area, care should be taken to protect pine plantations against this devastating pest.