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- Teste de susceptibilidade ao nemátode da madeira do pinheiro (bursaphelenchus xylophilus) - optimização para utilização em larga escalaPublication . Lima, Marta R. M.; Ramos, Miguel; Sampedro, Luis; Moreira, Xoaquín; Zas, Rafael; Marta W. VasconcelosA doença da murchidão do pinheiro é uma doença grave que afecta florestas de coníferas com uma elevada taxa de mortalidade, sendo causada pelo nemátode Bursaphelenchus xylophilus. Dado que este organismo foi recentemente introduzido na Europa, é importante determinar o grau de susceptibilidade de espécies florestais autóctones ao nemátode. Neste trabalho optimizou-se um teste de susceptibilidade para utilização num grande número de amostras. O teste baseia-se na capacidade de nemátodes virulentos atravessarem secções de 5 cm de ramos jovens, com cerca de 2 cm de diâmetro. O processo de optimização passou pela forja de recipientes de dimensões adequadas, criação de um modo de sustentar os ramos em posição vertical, optimização do volume de água onde a base do ramo fica mergulhada e criação de um modo de evitar a desidratação do topo do ramo após inoculação. O crescimento dos nemátodes em laboratório também passou por um scale-up para obtenção de nemátodes em grande quantidade, passando do crescimento em tubos de ensaio para sacos. O teste foi optimizado usando ramos de Pinus pinaster, mas pode ser adaptado a outras espécies.
- Susceptibility to the pinewood nematode (PWN) of four pine species involved in potential range expansion across EuropePublication . Silva, Marta Nunes da; Solla, Alejandro; Sampedro, Luis; Zas, Rafael; Vasconcelos, Marta W.The pine wilt disease (PWD), caused by the pinewood nematode (PWN) Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, is one of the most serious threats to pine forests worldwide. Here we studied several components of susceptibility to PWN infection in a model group of pine species widely distributed in Europe (Pinus pinaster Ait., P. pinea L., P. sylvestris L. and P. radiata D. Don), specifically concerning anatomical and chemical traits putatively related to nematode resistance, whole-plant nematode population after experimental inoculation, and several biochemical and physiological traits indicative of plant performance, damage and defensive responses 60 days post inoculation (dpi) in 3-year-old plants. Pinus pinaster was the most susceptible species to PWN colonization, with a 13-fold increase in nematode population size following inoculation, showing up to 35-fold more nematodes than the other species. Pinus pinea was the most resistant species, with an extremely reduced nematode population 60 dpi. Axial resin canals were significantly wider in P. pinaster than in the other species, which may have facilitated nematode dispersal through the stem and contributed to its high susceptibility; nevertheless, this trait does not seem to fully determinate the susceptible character of a species, as P. sylvestris showed similar nematode migration rates to P. pinaster but narrower axial resin canals. Nematode inoculation significantly affected stem water content and polyphenolic concentration, and leaf chlorophyll and lipid peroxidation in all species. In general, P. pinaster and P. sylvestris showed similar chemical responses after infection, whereas P. radiata, which co-exists with the PWN in its native range, showed some degree of tolerance to the nematode. This work provides evidence that the complex interactions between B. xylophilus and its hosts are species-specific, with P. pinaster showing a strong susceptibility to the pathogen, P. pinea being the most tolerant species, and P. sylvestris and P. radiata having a moderate susceptibility, apparently through distinct coping mechanisms.
- Intraspecific variation of anatomical and chemical defensive traits in Maritime pine (Pinus pinaster) as factors in susceptibility to the pinewood nematode (Bursaphelenchus xylophilus)Publication . Zas, Rafael; Moreira, Xoaquín; Ramos, Miguel; Lima, Marta R. M.; Silva, Marta Nunes da; Solla, Alejandro; Vasconcelos, Marta; Sampedro, LuisKey message Migration ability of the PWN through wood branch tissues of adult Maritime pine trees significantly differed among Iberian provenances and this variation was related to differences in anatomical and chemical defensive traits. Abstract The pinewood nematode or pine wilt nematode (PWN; Bursaphelenchus xylophilus) is one of the most dangerous threats to European coniferous forests, especially for the susceptible Maritime pine (Pinus pinaster), a valuable forest resource in South Western Europe. The PWN is vectored by beetles of the genus Monochamus (Coleoptera, Cerambycidae) and once inoculated in healthy branches, it quickly migrates downward to the main trunk through the resin canal system. Therefore, the anatomy of the resin canal system may modulate its migration and proliferation rates. Using material from nine Maritime pine Iberian provenances established in a common garden trial, we investigated whether these provenances differed in their (1) resin canal anatomy, (2) concentration of chemical defences (non-volatile resin and total polyphenolics) in stems and (3) ability of the PWN to migrate through the pine woody tissues in ‘in vitro’ bioassays. Whether variation in anatomical and chemical defensive traits relates to differences in PWN migration across populations was also investigated. Significant intraspecific variation in anatomical and chemical defensive traits and in nematode migration rates through pine tissues was observed. Moreover, the variation in nematode migration rate among pine provenances was related to differences in both anatomical and chemical features. Overall, this study highlights the role of plant genetics in the development of defensive traits against this harmful coniferous pest. The observed intraspecific variation should be taken into account when considering breeding as a strategy to provide areas of high risk of PWN with resistant genetic material.
- 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.
- Traumatic resin ducts induced by methyl jasmonate in Pinus sppPublication . López‑Villamor, Adrián; Zas, Rafael; Pérez, Andrea; Cáceres, Yonatan; Silva, Marta Nunes da; Vasconcelos, Marta; Vázquez‑González, Carla; Sampedro, Luis; Solla, AlejandroKey message Exogenous MJ does not alter the resin duct structure of pines in the cortex, but increases the number, density and mean size of resin ducts in the secondary xylem, particularly in Pinus sylvestris and P. radiata. Abstract Methyl jasmonate (MJ) is an organic compound capable of modulating defence responses in plants. Exogenous application of MJ has been shown to modify the structure of the resin canal system in conifers by inducing the formation of dense concentric bands of traumatic resin ducts in the xylem. Because inducibility of resin ducts has been little explored across pine species, 3-year-old Pinus pinaster, P. pinea, P. sylvestris and P. radiata trees were sprayed with 0, 25 and 50 mM solutions of MJ, and plant growth, external symptoms and histology were assessed 60 days after treatment. Exogenous application of MJ diminished primary or secondary growth in all species (61 and 25%, respectively) and caused needle damage in P. sylvestris. Exogenous MJ did not alter the resin duct structure of Pinus spp. in the cortex. In the secondary xylem, however, the effect of MJ differed considerably between species: ducts, duct density and area covered by ducts increased in P. sylvestris and P. radiata, but not in P. pinaster and P. pinea. In MJ 50 mM-treated trees, resin duct abundance peaked at the first half of the ring in P. sylvestris and at one-third distance from the previous ring in P. radiata. In MJ treated P. radiata trees, large traumatic axial resin ducts, 120–160 μm in diameter, were aligned in the secondary xylem. The study helps to elucidate macroevolutionary aspects of inducibility of resin-based defences in the genus Pinus, where varying responses to MJ could reveal different defence strategies among species.