Browsing by Author "Fraga, Irene"
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- Enzymes and secondary metabolites profiles of Gnomoniopsis smithogilvyi are affected by chestnut mediumPublication . Sampaio, Ana; Camelo, Verónica; Fraga, Irene; Gomes, A.; Sulyok, Michael; Gomes-Laranjo, José; Dias, Albino A.; Rodrigues, PaulaChestnut tree (Castanea sativa Mill) is a crop with high economic and social importance in Trás-os-Montes Region. The pre and post-harvest quality of its nuts can be affected by many factors, being the lasses dueto fungi very large. During the last decade a new endophyte fungus, Gnomoniopsis smithogilvyi, causing brown rot, has been isolated from both rotten and healthy fruits, and its growth seems to be related with the increase of air temperatura and rainfall during spring. The present study aims to understand the influence of chestnut substrate on G. smithogilvyi biochemistry, in arder to develop strategies to reduce its incidence in the fruit and improve the contrai of brown rot. lnitially, the presence of the enzymes involved in the decomposition of chestnuts, such as amylase, proteases, carboxymethylcellulase (CMCase), ~-glucosidase, xylanase, among others, was investigated. Further, some hydrolase activities were evaluated in two isolates of G. smithogilvyi incubated in potato (PDB) and chestnut media (CM) along an incubation period (3, 7 and 14 days), in arder to study the effects "isolate", "medium" and "incubation period" on enzymes production. Also, the synthesis of secondary metabolites in fungai dry biomass was assessed by Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Ali isolates produced the enzymes screened and, in general, the enzyme production varied between the isolates (P< 0.0000), the media (P< 0.0000) and along the incubation period (P< 0.0000). Amylase activity was positively correlated with xylanase (P< 0.0001), CMCase (P< 0.0001), and Avicelase {P< 0.01), xylanase with CMCase (P< 0.01) and ~-glucosidase with Avicelase (P< 0.0001 ). By contrast, ~-glucosidase was negatively correlated with CMCase {P< 0.01 ). Twenty secondary metabolites were detected along the incubation: eight in both isolates and media, tive and three only in isolates grew in PD o r CM, respectively. Some of these metabolites had been associated with other fungi and have known biological activities.
- Kaolin foliar spray induces positive modifications in volatile compounds and fruit quality of Touriga-Nacional red winePublication . Dinis, Lia Tânia; Pereira, Sandra; Fraga, Irene; Rocha, Sílvia M.; Costa, Carina; Martins, Cátia; Vilela, Alice; Arrobas, Margarida; Moutinho-Pereira, JoséSolar radiation and temperature play crucial roles in grapevine metabolic processes and are known to have a positive impact on grape berry composition; however, excessive exposure to these factors can be detrimental. Kaolin-based particle film technology has emerged as a valuable solution for mitigating the effects of heat and water stresses in vineyards. This work aimed to evaluate the effects of kaolin application on the phenolic composition, chromatic characteristics, oenological parameters, volatile compounds and sensory profile of red wine. The study was carried out in one growing season in the commercial vineyard “Quinta dos Aciprestes” in the Douro Superior sub-region. Twelve rows in triplicate of the Touriga-Nacional variety underwent foliar kaolin treatment (applied at the pre-veraison stage, at the manufacturerrecommended and -tested dosage of 5 % (w/v)), and another twelve rows comprised the nontreated control group. Kaolin increased the phenolic compound and tartaric acid concentrations (2.4 % and 20.8 % respectively), total acidity (2.4 %), the deep reddish colour of the berries, total and coloured anthocyanin (2.8 %), and total and polymeric pigments (3.6 %); meanwhile, a decrease was observed in pH (-1.4 %) and alcoholic degree (-4.8 %). No significant differences were observed in any sensory parameters between the wine from the kaolin-treated and control vines, but the tasters found the aroma of the former to be fruitier and more complex, with an agreeable acidic taste and persistence. It was possible to group the volatile compounds into two distinct groups based on the results of the Pearson’s correlation matrix. This grouping corresponds to the sensory descriptors common to each of the respective volatiles. Overall, the results further support the potential efficacy of utilising kaolin to alleviate summer-related stress in grapevines.