Browsing by Author "Pais, Isabel P."
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- Cryptogein and capsicein promote defence responses in Quercus suber against Phytophthora cinnamomi infectionPublication . Medeira, C.; Quartin, V.; Maia, I.; Diniz, I.; Matos, M.; Semedo, J.; Scotti Campos, P.; Ramalho, J. C.; Pais, Isabel P.; Ramos, P.; Melo, Eduardo P.; Leitao, A.; Cravador, A.The decline of cork oak (Quercus suber) stands in Iberian Peninsula is associated with infection by Phytophthora cinnamomi. Most Phytophthora species secrete elicitins, which can enhance defence reactions against some pathogens. Here cytological and physiological effects of the elicitins cryptogein and capsicein on cork oak root infection by P. cinnamomi were evaluated. The progression of the pathogen in root tissue and its effects on total fatty acid (TFA) composition of roots and leaves were analysed in seedlings. Net photosynthesis (P (n) ), stomatal conductance (g (s) ), chlorophyll a fluorescence measurements (quantum yield of linear electron transport I center dot (e) , photochemical quenching q (P,) non-photochemical quenching NPQ) and carotenoid determinations were carried out in well established (4 months) plants. In elicitin-treated roots, 2 days after inoculation, the pathogen which presented loss of viability and membrane degradation was mainly restricted to the intercellular spaces of the cortical parenchyma, and did not reach the vascular cylinder. Electron dense materials accumulated in the intercellular spaces of the cortex next to disorganized hyphae, suggested to be related with defence reactions. Cryptogein (or its interaction with P. cinnamomi) induced enhanced lipid synthesis in leaves, which may contribute to preserve membrane stability. P. cinnamomi decreased P (n) , g (s) , I center dot (e) , and q (P), whereas elicitin-treated plants displayed values similar to controls. Overall, the results indicated a resistance response of cork oak against this oomycete, induced by the elicitins.
- Sugar variation in healthy, blue mold infected and aureobasidium pullulans treated ‘rocha’ pearPublication . Ramalho, J. C.; Pais, Isabel P.; Silva, M. J.; Nunes, CarlaSoluble sugars variation in ‘Rocha’ pear was studied in healthy, infected with Penicillium expansum (blue mold) and treated with the antagonist Aureobasidium pullulans fruits. Pears from four pickings were analyzed after 1, 3 and 5 months of cold storage (-0.5 ºC, 95% RH). For each storage period fruits were inoculated and kept at room temperature (ca. 20 ºC) for 5 d and analyzed. After 1 month of cold storage sucrose increased from the first to the last picking, while fructose, glucose and sorbitol were stable in healthy fruits. After 5 d at room temperature non-inoculated fruits presented fructose and glucose rises and sorbitol decreases for the 4 harvest dates, while sucrose increased in earlier yielded fruits but decreased in the last two pickings. After infection with P. expansum, in general, was observed a tendency to decrease in all sugars. The application of the antagonist A. pullulans partly reverses such tendency. The antagonist alone causes lower disturbances in sugar contents, except in glucose that may present slight decreases. Considering only the fruits of the commercial harvest date (DC3), sugars tend to increase along cold storage (except sucrose), particularly in healthy fruits and for most cases of both blue mold and antagonist inoculated fruits. On the other hand, the tendency for sugar decrease in P. expansum infected fruits, reported for 1 month of cold storage, is still detectable for glucose and sucrose after 3 months, and glucose, fructose and sorbitol after 5 months. After 3 and 5 months of storage, the maintenance of sugar content in fruits of the DC3 inoculated with both blue mold and the antagonist was not as clear as for 1 month. Data suggested that cold storage was beneficial for sugar increase of healthy fruits, except for sucrose. In the DC3 fruits, sugar loss caused by P. expansum was higher after 1 month of storage, but the use of the antagonist A. pullulans partly reverses that tendency.