Browsing by Author "Mota, Manuel"
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- Characterization of the pinewood nematode, bursaphelenchus xylophilus-pinus system in Portugal: phytochemical, histopathological, molecular, and biotechnological approachesPublication . Mota, Manuel; Barbosa, Pedro; Rodrigues, Ana M.; Silva, Inês Vieira da; Ascensão, Lia; Silva, M. Nunes da; Ferreira, António C. Silva; Vasconcelos, Marta W.; Faria, Jorge M. S.; Sena, Inês; Ribeiro, Bruno; Barroso, José G.; Pedro, Luis G.; Trindade, Helena; Figueiredo, A. CristinaThe pinewood nematode, Bursaphelenchus xylophilus, is one of the main threats affecting Portuguese maritime pine (Pinus pinaster). Several research teams have joined efforts to better understand the plant-nematode system. Over 150 essential oils (EO), as well as several EO fractions and decoction waters have been evaluated, Ruta graveolens, Satureja montana, Thymbra capitata, Thymus pulegioides, and T. vulgaris EOs being the most nematotoxic. Two-year-old P. pinaster, P. pinea, P. sylvestris, and P. halepensis were inoculated with a virulent PWN Portuguese isolate, and comparatively evaluated with non-inoculated and wounded plants to understand the plant-nematode interaction and the role of plant volatiles. Histological studies showed that the number of nematodes increased in P. pinaster and P. sylvestris with disease progression, and 7 weeks after inoculation all pine tissues were severely damaged. PWN distribution in P. pinea and P. halepensis was nearly restricted to the inoculated area; no clear change was observed in the stem tissues. Pine species volatiles showed the existence of chemotypes in some cases. Key volatile organic compounds, such as 4-hexen-1-ol, involved in P. pinaster response against the nematode have also been identified using non-destructive methods, with the potential to be used as biomarkers for early detection of infected trees. In vitro co-cultures of the host with parasite have also been established as a biotechnological tool to evaluate the effect of nematotoxic addition and assess their phytotoxicity to the host. Molecular approaches have addressed the changes in α-pinene synthase gene expression in susceptible P. pinaster and non-susceptible P. pinea, following nematode invasion. Preliminary results showed an increased expression of this gene in P. pinea, contrary to P. pinaster which revealed the same expression level in infected and non-infected controls.
- In vivo volatile organic compounds analysis in pinus pinaster after infection with bursaphelenchus xylophilusPublication . Silva, M. Nunes da; Ferreira, António C. Silva; Mota, Manuel; Vasconcelos, Marta W.The pine wilt disease (PWD), caused by the nematode Bursaphelenchus xylophilus, is devastating for Pinus pinaster plantations, leading to the loss of thousands of trees every year worldwide. Despite the important research efforts of the past decades, no effective strategies against the PWN have been developed and the physiological aspects related to disease resistance remain largely unknown. In this work, 1-yr-old P. pinaster plants were inoculated with ca. 1000 B. xylophilus nematodes or with water (controls). Three and 21 days post inoculation (dpi), volatile organic compounds (VOCs) were analysed through a non-invasive methodology: VOCs were concentrated in a personalized acrylic chamber for 60 min and subsequently collected with a DVB/CAR/PDMS fibre for 30 min, after which they were identified by gas chromatography/ mass spectrometry (GC/MS). An additional set of inoculated plants was sacrificed three and 21 dpi for total stem nematode counting. Results showed that nematodes successfully reproduced throughout the experimental period, reaching ca. 3000 nematodes per plant just 21 dpi. Compared with control plants, total VOCs, especially monoterpenes, significantly increased three dpi in inoculated plants, probably as part of P. pinaster chemical defence mechanisms against the pathogen. VOCs dramatically decreased 21 dpi, most likely due to tissue damage induced by B. xylophilus, demonstrating the susceptible character of P. pinaster. At 3 dpi, there was increased biosynthesis of almost all VOCs, specially α-pinene and ß-myrcene (ca. 4-fold), known to accumulate in leaf tissues to repel herbivores and pathogens. Sabinene and 3-carene also increased significantly in infected plants (4.1- and 5-fold, respectively), 21 dpi, which suggests that the biosynthesis of different defence-related VOCS is triggered at different stages of the disease. 4-hexen- 1-ol, a known allelopathic agent, was only found in inoculated plants, perhaps as a strategy to attract B. xylophilus predators. These findings could be of utmost importance for the precocious diagnostic of the PWD.
- In vivo volatile organic compounds analysis in Pinus pinaster after infection with Bursaphelenxus xylophilusPublication . Silva, M. Nunes da; Ferreira, António C. Silva; Mota, Manuel; Vasconcelos, Marta W.