Browsing by Author "Sousa, N."
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- Alpha cinnamomin elicits a defence response against Phytophthora cinnamomi in Castanea sativaPublication . Medeira, C.; Maia, I.; Ribeiro, C.; Candeias, I.; Melo, Eduardo P.; Sousa, N.; Cravador, A.Phytophthora cinnamomi and P. cambivora are considered as the causal agents of Castanea sativa ink disease. These soil-borne plant pathogens invade and destroy the root system leading to the death of the trees. Most Phytophthora species secrete elicitins, a group of unique highly conserved proteins that are able to enhance plant defence responses in a systemic acquired resistance manner against infection by several pathogens. A cluster of four elicitin genes was identified in P. cinnamomi. In previous works one of these elicitins, α- cinnamomin was shown to restrict the invasion of root cortical tissues by P. cinnamomi preventing vascular colonization in cork and holm oak. In the present work, roots of chestnut plantlets grown in vitro were allowed to absorb α-cinnamomin at 100 μg/ml for two days before being inoculated with P. cinnamomi. The effects of this elicitin on host-pathogen interaction were studied at histological and ultrastructural levels. P. cinnamomi was restricted to the outer cortex of 65% of the roots pre-treated with α-cinnamomin. In these roots, the vascular cylinders were free of pathogen. On the contrary, the pathogen reached the vascular cylinder, penetrating the phloem and xylem vessels in all non-treated assayed roots. The signs of pathogen degradation in the cortical parenchyma, mainly in the intercellular spaces, and the increase of a physical barrier in epidermal and sub-epidermal cell wall-media lamella and intercellular spaces by impregnation with phenol-like compounds strongly suggest that α-cinnamomin induced in chestnut defence reactions against P. cinnamomi.
- Anti-Phytophthora cinnamomi activity of Phlomis purpurea plant and root extractsPublication . Neves, D.; Caetano, P.; Oliveira, J. V.; Maia, Cristiana; Sousa, N.; Salgado, M.; Dionisio, L.; Magan, N.; Cravador, A.Phlomis purpurea (Lamiaceae), found in Quercus suber and Quercus ilex ssp. rotundifolia forest habitats in southern Portugal, is a non-host for the oomycete Phytophthora cinnamomi, the main biotic factor involved in cork oak and holm oak decline in the Iberian Peninsula. The effect of P. purpurea crude ethanol root extract was evaluated in vitro on P. cinnamomi mycelial growth, sporangial production, zoospore release and germination as well as on chlamydospore production and viability. The protection of cork oak against infection by the pathogen was also evaluated in planta. At 10 mg ml-1, in vitro inhibition of the pathogen structures was 85-100 %. In addition, P. purpurea plants were shown to protect Q. suber and Q. ilex from P. cinnamomi infection and to reduce the inoculum potential in glasshouse trials, indicating the ability to reduce root infection by the pathogen. The results suggest that P. purpurea has the potential to reduce disease spread and that their root extracts could provide candidate substances for control of the important pathogen, P. cinnamomi. © 2013 KNPV.