Browsing by Author "Carvalho, Susana M. P."
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- Assessing the effectiveness of different Pseudomonas syringae pv. actinidiae pre-inoculation procedures to promoting disease visual symptoms in adult kiwifruit plantsPublication . Santos, Miguel G.; Silva, Marta Nunes da; Gallego, Pedro P.; Vasconcelos, Marta W.; Carvalho, Susana M. P.
- Avoiding high relative air humidity during critical stages of leaf ontogeny is decisive for stomatal functioningPublication . Fanourakis, Dimitrios; Carvalho, Susana M. P.; Almeida, Domingos M. P.; Domingos, P.F.; Heuvelink, EpPlants of several species, if grown at high relative air humidity (RH >= 85%), develop stomata that fail to close fully in case of low leaf water potential. We studied the effect of a reciprocal change in RH, at different stages of leaf expansion of Rosa hybrida grown at moderate (60%) or high (95%) RH, on the stomatal closing ability. This was assessed by measuring the leaf transpiration rate in response to desiccation once the leaves had fully expanded. For leaves that started expanding at high RH but completed their expansion after transfer to moderate RH, the earlier this switch took place the better the stomatal functioning. Leaves initially expanding at moderate RH and transferred to high RH exhibited poor stomatal functioning, even when this transfer occurred very late during leaf expansion. Applying a daily abscisic acid (ABA) solution to the leaves of plants grown at continuous high RH was effective in inducing stomatal closure at low water potential, if done before full leaf expansion (FLE). After FLE, stomatal functioning was no longer affected either by the RH or ABA level. The results indicate that the degree of stomatal adaptation depends on both the timing and duration of exposure to high RH. It is concluded that stomatal functionality is strongly dependent on the humidity at which the leaf completed its expansion. The data also show that the effect of ambient RH and the alleviating role of ABA are restricted to the period of leaf expansion.
- Biochemical markers to predict internal browning disorders in ‘Rocha’ pear during storage under high CO2Publication . Deuchande, Teresa; Larrigaudière, Christian; Guterres, Umbelina; Carvalho, Susana M. P.; Vasconcelos, Marta W.BACKGROUND: The aim of this studywas to identify biochemical markers to predict internal browning disorders (IBD) in 'Rocha' pear. Fruits from five orchards were stored for 45 days under cold air followed by 100 days in browning-inducing controlled atmosphere (CA) conditions (1 kPaO(2) + 10 kPaCO(2)). RESULTS: Relationships between concentrations of ethanol (EtOH), acetaldehyde (AcDH) and ascorbic acid (AA), activities of peroxidase (POX) and polyphenoloxidase (PPO) and IBD incidence were established. The partial least square (PLS) model using the most promising markers, EtOH and AcDH, explained 89% of the variance in IBD incidence, whereas the univariate models based on the same markers explained between 89 and 94%. In contrast, the models based on AA levels and AA depletion rate only explained 57 and 82% of the variance in IBD incidence respectively. Model validation confirmed the robustness of EtOH for the prediction (R-2 = 0.91, RMSE= 11.1) and allowed proposing a threshold level of 30 mu L EtOH L-1 above which IBD may occur. Using this threshold value, the storage time limit associated with the occurrence of the first IBD symptoms was predicted with an acceptable RMSE of 9 days. CONCLUSION: Thiswork clearly identifies biochemical IBDmarkers for ` Rocha' pear and shows that dynamic changes in ethanol concentration during the beginning of storagemay be used to predict IBD development. Therefore the results presented herein represent a major step forward in the prediction of IBD in 'Rocha' pear.
- Controlo da altura de plantas ornamentais: alternativas sustentáveis aos reguladores de crescimentoPublication . Carvalho, Susana M. P.; Almeida, Domingos P. F.; Heuvelink, EpA necessidade de encontrar estratégias sustentáveis eficazes no controlo da altura da planta é actualmente um grande desafio que se coloca à horticultura ornamental protegida. Este estudo teve como objectivo: (1) analisar a informação disponível acerca dos factores que afectam a altura das plantas; (2) compreender os mecanismos fisiológicos envolvidos no processo de alongamento do caule; (3) definir alternativas sustentáveis para produzir plantas compactas, reduzindo ao mínimo a aplicação de „reguladores químicos de crescimento‟. Concluiu-se que manter uma temperatura nocturna superior à temperatura diurna (DIF negativa ou tratamento DROP) ou a alteração do espectro luminoso (elevado rácio vermelho/vermelho-longínquo) apresentam um forte potencial como métodos não químicos no controlo da altura de várias espécies de plantas ornamentais. Oaumento do rácio vermelho/vermelho-longínquo, poderáser efectuado de diferentes modos incluindo a utilização defilmes fotosselectivose/ourecorrendoa um conjunto de medidas facilmente aplicáveis tais como:(i) evitar densidades de plantação muito elevadas; (ii) utilização de luz suplementar com elevado rácio vermelho/vermelho-longínquo (ex. lâmpadas de assimilação em substituição de lâmpadas incandescentes); (iii) evitar a exposição das plantas à radiação do crepúsculo (devido à diminuição natural do rácio vermelho/vermelho-longínquo). O stress mecânico é também uma medida eficaz para a manutenção de plantas compactas em determinadas espécies. Paralelamente, o recurso ao Melhoramento de plantas no sentido de seleccionar cultivares ananicantes poderá ser bastante promissor. Porém, na maioria dos casos, não será uma medida única que permitirá a obtenção de plantas compactas, mas a combinação de várias estratégias.
- Controlo da altura de plantas ornamentais: alternativas sustentáveis aos reguladores de crescimentoPublication . Carvalho, Susana M. P.; Almeida, Domingos P. F.; Heuvelink, Ep
- Controlo da altura de plantas ornamentais: alternativas sustentáveis aos reguladores de crescimentoPublication . Carvalho, Susana M. P.; Almeida, Domingos P. F.; Heuvelink, Ep
- Does salicylic acid alleviate the impacts on growth, development and productivity of “flavescence dorée” in Portuguese “Vinhos Verdes” grapevines?Publication . Oliveira, Manuel J.R.A.; Vasconcelos, Marta; Castro, Sandra; Bertaccini, Assunta; Carvalho, Susana M. P.“Flavescence dorée” (FD) is a quarantine disease of great concern to the stability and sustainability of the wine industry, due to drastic harvest losses and death of infected plants. Previous studies have suggested that salicylic acid (SA) may improve the plant resistance against grapevine diseases, but no studies have been carried out for FD. The effect of 25 mM SA applied at the flowering stage to healthy and FD infected grapevines cultivar Loureiro was evaluated in a field trial. The evaluation of development and productivity (percentage of budburst, fertility index, time to veraison, and chlorophyll content) and grape quality parameters (degree Brix and titrable acidity) was carried out. Fertility index and chlorophyll content were significantly lower in infected plants and SA partly reduced the FD symptoms, since at veraison these plants did not show significant differences when compared to healthy plants for those parameters. However the productivity was significantly lower in the infected plants, with no significant effect of SA application. The berry quality was no significantly different comparing healthy and infected plants or SA-treated and untreated plants.
- Early pathogen recognition and antioxidant system activation contributes to actinidia arguta tolerance against pseudomonas syringae pathovars actinidiae and actinidifoliorumPublication . Nunes da Silva, M.; Vasconcelos, M. W.; Gaspar, M.; Balestra, G. M.; Mazzaglia, A.; Carvalho, Susana M. P.Actinidia chinensis and A. arguta have distinct tolerances to Pseudomonas syringae pv. actinidiae (Psa), but the reasons underlying the inter-specific variation remain unclear. This study aimed to integrate the metabolic and molecular responses of these two kiwifruit species against the highly pathogenic Psa and the less pathogenic P. syringae pv. actinidifoliorum (Pfm) bacterial strains. Disease development was monitored weekly till 21 days post inoculation (dpi), analysing a broad number and variety of parameters including: colony forming units (CFU), foliar symptoms, total chlorophylls, lipid peroxidation, soluble polyphenols, lignin and defense-related gene expression. At the end of the experimental period A. chinensis inoculated with Psa presented the highest endophytic bacterial population, whereas A. arguta inoculated with Pfm showed the lowest values, also resulting in a lower extent of leaf symptoms. Metabolic responses to infection were also more pronounced in A. chinensis with decreased total chlorophylls (up to 55%) and increased lipid peroxidation (up to 53%), compared with non-inoculated plants. Moreover, at 14 dpi soluble polyphenols and lignin concentrations were significantly higher (112 and 26%, respectively) in Psa-inoculated plants than in controls, while in A. arguta no significant changes were observed in those metabolic responses, except for lignin concentration which was, in general, significantly higher in Psa-inoculated plants (by at least 22%), comparing with control and Pfm-inoculated plants. Genes encoding antioxidant enzymes (SOD, APX and CAT) were upregulated at an earlier stage in Psa-inoculated A. arguta than in A. chinensis. In contrast, genes related with phenylpropanoids (LOX1) and ethylene (SAM) pathways were downregulated in A. arguta, but upregulated in A. chinensis in the later phases of infection. Expression of Pto3, responsible for pathogen recognition, occurred 2 dpi in A. arguta, but only 14 dpi in A. chinensis. In conclusion, we found that A. arguta is more tolerant to Psa and Pfm infection than A. chinensis and its primary and secondary metabolism is less impacted. A. arguta higher tolerance seems to be related with early pathogen recognition, the activation of plant antioxidant system, and to the suppression of ET and JA pathways from an earlier moment after infection.
- Effect of blanching, storage and drying conditions on the macro-composition, color and safety of mealworm Tenebrio molitor larvaePublication . Ribeiro, José Carlos; Marques, João Pedro; Fernandes, Tânia R.; Pintado, Manuela Estevez; Carvalho, Susana M. P.; Cunha, Luís MiguelFor food applications, the processing conditions applied to edible insects should present low energy requirements and environmental impact, while also assuring high quality and safety. The main goal of this study was to assess how different blanching, storage and drying conditions influence the quality and safety of Tenebrio molitor larvae. The different operations included blanching treatments (water-immersion or steaming), post-blanching storage (freezing or refrigeration) and drying methods (oven, microwave or freeze dryer). To monitor the impact on the quality of T. molitor dry matter content, water activity (aw), color and macro-nutrient composition were evaluated, while microbiological analyses were performed to assess the impacts on quality and safety. Blanching, particularly immersion-blanching, improved the lightness of the larvae, both before and after drying. Both blanching treatments reduced the Total Viable Count (TVC) and Enterobacteriaceae loads. Regarding the drying methods, freeze drying led to the best color conservation, while drying with an oven led to the lowest moisture content and aw. The application of drying methods further contributed to the reduction of TVC and Enterobacteriaceae, assuring low loads even after 3 months of storage, with the freeze dryer resulting in the lowest reductions, including an increase in yeast and mold count.
- Effect of different pre-inoculation procedures on leaf spotting appearance in adult kiwifruit plants artificially inoculated with Pseudomonas syringae pv. actinidiaePublication . Santos, Miguel G.; Silva, Marta Nunes da; Gallego, Pedro P.; Vasconcelos, Marta W.; Carvalho, Susana M. P.Phytopathology studies most often rely on laboratory, greenhouse or field experiments in which plants are artificially inoculated using a variety of pre-inoculation procedures that aim to improve plant infection success. Concerning the Kiwifruit Bacterial Canker (KBC), whose aetiological agent is the bacterium Pseudomonas syringae pv. actinidiae (Psa), the pre-inoculation procedures most often target leaf tissues, promoting bacterial colonization through natural (e.g., stomata) or artificial openings (e.g., leaf wounds). However, the variability in pre-inoculation methods can influence the infection dynamics, making pathogenicity analysis amongst different research studies very complex. Here, four pre-inoculation procedures were tested in adult kiwifruit plants (Actinidia chinensis var. deliciosa ‘Tomuri’; lignified 15-month-old plants grown in pots) for their effect on leaf spotting appearance at 21 days after inoculation. These procedures consisted of: (i) plant enclosure in a plastic bag (maintained 24 h before and 24 h after inoculation; BAG), (ii) leaf wounding with three superficial cuts (CUTS), (iii) plant maintenance at 5 ℃ for 24 h (COLD) and (iv) a combination of all these procedures (ALL). Plants mock-inoculated with Ringer’s solution were included in the experiment as control. Results showed that BAG was the treatment with highest efficacy in causing appearance of leaf spots, since plants showed 7.1, 15 and 40 times more leaf spots than plants from ALL, CUTS and COLD, respectively. Furthermore, treatments ALL, CUTS and COLD did not appear to be suitable pre-inoculation procedures for promoting KBC foliar symptoms. This study highlights the importance of following precise pre-inoculation procedures in plant artificial inoculation with Actinidia chinensis – Psa, where leaf symptoms appearance is commonly utilized in disease severity analysis.