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- Study of symptoms and gene expression in four Pinus species after pinewood nematode infectionPublication . Franco, Albina R.; Santos, Carla; Roriz, Mariana; Rodrigues, Rui; Lima, Marta R. M.; Vasconcelos, Marta W.Pine wilt disease, caused by the pinewood nematode Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle, is originating severe infections in pine trees. The disease is detected when external symptoms appear (e.g. needle chlorosis), but trees could remain asymptomatic for long periods and serve as a long-term host. The primary goal of this study was to assess the effect of inoculation with an avirulent isolate of B. xylophilus (C14-5) on different Pinus spp. seedlings (P. sylvestris, P. nigra, P. pinea and P. pinaster). At the same time, seedlings were also inoculated with a virulent strain, HF, in order to compare the phenotypic and genomic results of the two types of inoculations. The effect of inoculation was determined in terms of expression of various Pinus genes potentially involved in the response to the disease.The results suggest that P. pinea and P. nigra are more resistant to infection by the nematode than P. sylvestris and P. pinaster. The phenotypic and genetic differences were more marked among P. pinea and P. pinaster.
- Susceptibility evaluation of Picea abies and Cupressus lusitanica to the pinewood nematode, Bursaphelenchus xylophilusPublication . Silva, M. Nunes da; Lima, M. R. M.; Vasconcelos, Marta W.Pine wilt disease (PWD), recently introduced into Europe, is caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus and is a devastating illness that affects mainly pine trees. It is known that the PWN is capable of infecting other conifers; however, there is currently no information on which other plant species may be susceptible to PWD. In this study, the potential susceptibility of two common species of European forests, Picea abies and Cupressus lusitanica, to PWN was assessed through the monitoring of visual external symptoms, dimension and localization of the nematode population in stems, quantification of total chlorophyll, total soluble phenolics and lignin, at 7, 14, 21 and 28days after inoculation. The degree of susceptibility was established through the comparison of symptoms with Pinus pinaster, a well-known PWN host. Furthermore, the stem ultrastructure of P.abies, C.lusitanica and Pn.pinaster was analysed by scanning electron microscopy. The results suggest that P.abies and C.lusitanica are resistant to PWN, and that lignin biosynthesis in these species is affected at an early stage of the infestation. Nevertheless, P.abies seems to be a compatible host that could act as a repository for PWN.