Percorrer por autor "Carvalho, Susana M. P."
A mostrar 1 - 10 de 51
Resultados por página
Opções de ordenação
- Antimicrobial potential of six plant essential oils against Pseudomonas syringae pv. actinidiae: in vitro activity and in planta efficacy do not always alignPublication . Silva, Marta Nunes da; Santos, Miguel G.; Vasconcelos, Marta W.; Carvalho, Susana M. P.Plant essential oils (EOs) are attracting interest as ecofriendly alternatives to antibiotics and copper-based control of kiwifruit bacterial canker (KBC), caused by Pseudomonas syringae pv. actinidiae (Psa). This study chemically profiled six EOs (anise, basil, cardamom, cumin, fennel, and laurel) and evaluated their antimicrobial activity both in vitro and in planta. The in vitro assay targeted four strains, two of Psa and two of the low-virulent P. syringae pv. actinidifoliorum (Pfm), whereas the in planta assay focused on the highly virulent Psa7286 strain, assessed under preventive and curative application regimes (i.e., 14 days pre- or post-inoculation, respectively). Cumin, with cuminaldehyde as its major component (48%), was the most effective EO in vitro, significantly inhibiting growth at 5–10% concentration, whereas anise, rich in anethole (89%), was consistently the least effective one. However, the in planta application of the EOs produced antimicrobial effects that differed markedly from in vitro results and showed strong dependence on the timing of application. Preventive treatment significantly reduced Psa endophytic populations in basil (70%), anise (54%), laurel (42%), and cumin (35%) compared to untreated plants. In contrast, when the EOs were applied post-inoculation (curative treatment), a significant decrease in Psa colonization was observed in laurel (81%), cardamon (70%), cumin (31%) and fennel (29%). Although plant EOs are gaining momentum in the control of Psa and other diseases, translation from in vitro to in planta efficacy is not direct and is strongly timing-dependent, which underscores the need to perform validation trials in planta and to fine-tune application schedules for the integrated management of KBC.
- 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.
- Atmosfera controlada dinâmica na prevenção do acastanhamento interno em pera rocha: eficácia dos sensores de etanol e de fluorescência de clorofilasPublication . Deuchande, Teresa; Carvalho, Susana M. P.; Larrigaudière, Christian; Fidalgo, Fernanda; Guterres, Umbelina; Isidoro, Nélson; Vasconcelos, MartaA pera ‘Rocha’ é suscetível ao desenvolvimento de acastanhamento interno (AI) durante o armazenamento prolongado em atmosfera controlada estática (ACE). Este estudo teve como objetivo avaliar o potencial da atmosfera controlada dinâmica (ACD) monitorizada por dois tipos de sensor (etanol e fluorescência de clorofilas) na prevenção do AI em pera ‘Rocha’, com enfase no metabolismo fermentativo e sistema antioxidante. Neste estudo, peras de um pomar foram armazenadas em três câmaras comerciais de atmosfera controlada durante 145 dias, com as seguintes condições de armazenamento: 1) ACD monitorizada por um sensor de etanol (ACD-EtOH); 2) ACD monitorizada por um sensor de fluorescência de clorofilas (ACD-FC); 3) ACE. No final do armazenamento os frutos em ACD-FC e ACE não foram afetados por AI, ao contrário dos frutos armazenados em ACD-EtOH, os quais apresentaram uma incidência de 15% após 125 dias e 20% após 145 dias de armazenamento. A elevada incidência de AI nos frutos armazenados em ACD-EtOH após 125 dias pareceu estar maioritariamente relacionada com os elevados níveis de etanol observado nestes frutos, comparativamente com os níveis detetados nos frutos da ACD-FC e ACE. Embora, após 125 dias, tenha ocorrido uma diminuição dos níveis de ácido ascórbico nos frutos da ACD-EtOH, após 145 dias os frutos superaram este decréscimo e os valores foram superiores aos registados nos frutos das outras condições de armazenamento. Estes resultados sugerem que a utilização do sensor de fluorescência de clorofilas para ajustar os níveis de oxigénio durante o armazenamento em ACD é uma estratégia eficaz na prevenção do AI em pera "Rocha". Pelo contrário, a informação dada pelo sensor de etanol parece ser insuficiente para evitar a indução do metabolismo fermentativo. Os resultados sugerem ainda, que a principal causa do AI em pera ‘Rocha’ poderá estar, primariamente relacionada com o metabolismo fermentativo.
- 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.