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- Exogenous systemin peptide treatment in olive alters Bactrocera oleae oviposition preferencePublication . Sánchez, Luiza; Cunha, Ana E.; Rodrigues, Nuno; Pereira, José Alberto; Baptista, PaulaThe olive fruit fly, Bactrocera oleae (Rossi), is a key pest of the olive crop, whose control relies mostly on the use of insecticides. Plant peptides may represent a more environmentally-friendly tool to manage olive fly, due to their recognized role to activate and/or prime plant defence responses against pests. In this work, behavioural experiments (no-choice and two-choice) and analysis of volatile compounds were carried out to evaluate the impact of the exogenous application of the peptide systemin to olive tree on olive fly infestation, and to elucidate its mode of action to prime plant defence. The treatment of olive branches with 10 nM systemin showed to confer protection against olive fly, by reducing significantly the ovipositions (up to 3.0-fold) and the number of infested fruits (up to 2.9-fold) when compared to non-treated branches. This protective effect was even detected in neighbouring non-treated branches, suggesting the ability of systemin to trigger plant-to-plant communication. The deterrent activity of the primed olives was associated with the emission of the volatiles 2-ethyl-1-hexanol, 4-tert-butylcyclohexyl acetate and 1, 2, 3-trimethyl-benzene, which were negatively correlated with oviposition and fly infestation. Systemin has also showed to trigger the biosynthesis of specific volatiles (esters) in olives in response to fly attacks. Overall, the observed protection conferred by systemin against olive fly is likely due to the emission of specific volatiles that can act as a defence and/or as signalling molecules to upregulate the plant defence response. Thus, systemin represents a novel and useful tool to manage olive fruit fly.
- Identification of leaf volatiles from olive (Olea europaea) and their possible role in the ovipositional preferences of olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae)Publication . Malheiro, Ricardo; Casal, Susana; Cunha, Sara C.; Baptista, Paula; Pereira, J.A.The olive fly, Bactrocera oleae (Rossi), is a monophagous pest that displays an oviposition preference among cultivars of olive (Olea europaea L.). To clarify the oviposition preference, the olive leaf volatiles of three olive cultivars (Cobrançosa, Madural and Verdeal Transmontana) were assessed by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) at six different periods of olive fruit maturation and degrees of infestation. A total of 39 volatiles were identified, mainly esters and alcohols, with a minor percentage of aldehydes, ketones and terpenic compounds, including sesquiterpenes. At sampling dates with higher degrees of infestation, cv. Cobrançosa had, simultaneously, significantly lower infestation degrees and higher volatile amounts than the other two cultivars, with a probable deterrent effect for oviposition. The green leaf volatiles (GLVs) (Z)-3-hexen-1-ol and (Z)-3-hexen-1-ol acetate) were the main compounds identified in all cultivars, together with toluene. The abundance of GLVs decreas ed significantly throughout maturation, without significant differences among cultivars, while toluene showed a general increase and positive correlation with olive fly infestation levels. The results obtained could broaden our understanding of the roles of various types and amounts of olive volatiles in the environment, especially in olive fly host selection and cultivar preference.
- Bacterial disease induced changes in fungal communities of olive tree twigs depend on host genotypePublication . Gomes, Teresa; Pereira, J.A.; Lino-Neto, Teresa; Bennett, Alison E.; Baptista, PaulaIn nature, pathogens live and interact with other microorganisms on plant tissues. Yet, the research area exploring interactions between bacteria-fungi and microbiota-plants, within the context of a pathobiome, is still scarce. In this study, the impact of olive knot (OK) disease caused by the bacteria Pseudomonas savastanoi pv. savastanoi (Psv) on the epiphytic and endophytic fungal communities of olive tree twigs from three different cultivars, was investigated in field conditions. The ITS-DNA sequencing of cultivable fungi, showed that OK disease disturbs the resident fungal communities, which may reflect changes in the habitat caused by Psv. In particular, a reduction on epiphyte abundance and diversity, and changes on their composition were observed. Compared to epiphytes, endophytes were less sensitive to OK, but their abundance, in particular of potential pathogens, was increased in plants with OK disease. Host genotype, at cultivar level, contributed to plant fungal assembly particularly upon disease establishment. Therefore, besides fungi - Psv interactions, the combination of cultivar - Psv also appeared to be critical for the composition of fungal communities in olive knots. Specific fungal OTUs were associated to the presence and absence of disease, and their role in the promotion or suppression of OK disease should be studied in the future.
- Comportamento e atitudes dos consumidores de azeite de oliveiras centenárias em PortugalPublication . Cabo, Paula; Rodrigues, Nuno; Pereira, J.A.; Baptista, PaulaEste trabalho pretende compreender as perceções e atitudes dos consumidores portugueses em relação ao azeite de oliveiras centenárias. Para tal, foi realizado um estudo transversal com base numa amostra de 1203 indivíduos. Os resultados mostram que parte significativa dos entrevistados (45,4%) conhece/consome azeite de oliveiras centenárias e tem uma imagem positiva do mesmo, ligada a atributos como "qualidade", "características organoléticas" e preservação do "património cultural" e "biodiversidade". Os fatores de diferenciação mais frequentemente sinalizados foram "características únicas", "tradicional", "maior qualidade" e "confiança no sabor". Embora 16,2% dos entrevistados vejam o produto como "preço elevado", apenas 18,9% não estão dispostos a pagar mais por uma garrafa de azeite.
- Impact of plant genotype and plant habitat in shaping bacterial pathobiome: a comparative study in olive treePublication . Mina, Diogo; Pereira, J.A.; Lino-Neto, Teresa; Baptista, PaulaPlant-inhabiting microorganisms interact directly with each other affecting disease progression. However, the role of host plant and plant habitat in shaping pathobiome composition and their implication for host susceptibility/resistance to a particular disease are currently unknown. For the elucidation of these questions, both epiphytic and endophytic bacterial communities, present in asymptomatic and symptomatic twigs from olive cultivars displaying different susceptibilities to olive knot (OK) disease, were investigated using culturing methods. OK disease was the main driver of the bacterial community, causing changes on their diversity, abundance and composition. OK disease effect was most notorious on OK-susceptible cultivar and when considering the endophytic communities. Plant habitat (epiphytes vs. endophytes) also contributed to the bacterial community assembling, in particular on symptomatic twigs (knots) of OK-susceptible cultivar. In contrast, host cultivar had little effect on the bacterial community composition, but OK-symptomatic twigs (knots) revealed to be more affected by this driver. Overall, the pathobiome seems to result from an intricate interaction between the pathogen, the resident bacteria, and the plant host. Specific bacterial genera were associated to the presence or absence of OK disease in each cultivar. Their ability to trigger and/or suppress disease should be studied in the future.
- Bacterial dynamics and exchange in plant-insect interactionsPublication . Cameirão, Cristina; Pereira, José Alberto; Tavares, Rui; Lino-Neto, Teresa; Baptista, PaulaIn nature, plants and insects engage in intricate interactions. Despite the increasing knowledge of the microbiomes of plants and insects, the extent to which they exchange and alter each other’s microbiomes remains unclear. In this work, the bacterial community associated with nymphs of Philaenus spumarius (Hemiptera: Aphrophoridae), the stems of Coleostephus myconis where the nymphs were feeding, and the foam produced by the nymphs, were studied by culture-dependent and -independent approaches, with an attempt to elucidate the exchange of bacteria between plants and insects. The results suggest that both approaches complement each other, as many bacterial genera identified by metabarcoding were not detected by culturing, and vice versa. Overall, stems and foam exhibited higher bacterial diversity than nymphs, with all the samples showing enrichment in bacteria known to provide diverse benefits to their host. Stems and foam were the most similar in bacterial composition, but Burkholderiaceae and Moraxellaceae dominated the stems, whereas Rhizobiaceae and Sphingobacteriaceae dominated the foam. Nymphs exhibit the most distinct bacterial composition, yet more similar to that found in the stem compared to the foam. Indeed, nymphs were enriched on endosymbiotic bacteria, mostly Candidatus Sulcia and Sodalis, not found in the stem and foam. Nevertheless, during feeding, nymphs appeared to exchange several bacteria genera with C. myconis, with a significant number being incor- porated into the bacteriome of the nymph. The genera Curvibacter, Cutibacterium, Methylobacterium, Pseudomonas and Rhizobium are likely the most exchanged. Nymphs also appear to exchange bacteria to the foam, notably species from the Enhydrobacter, Pseudomonas, Rhizobium and Roseomonas genera. More studies to infer the functions of the shared bacteria between P. spumarius-C. myconis are needed.
- Antimicrobial activity and bioactive compounds of portuguese wild edible mushrooms methanolic extractsPublication . Barros, Lillian; Calhelha, Ricardo C.; Vaz, Josiana A.; Ferreira, Isabel C.F.R.; Baptista, Paula; Estevinho, Leticia M.The antimicrobial properties of phenolic extracts of Portuguese wild edible mushroom species (Lactarius deliciosus, Sarcodon imbricatus and Tricholoma portentosum) against pathogens were investigated. The minimal inhibitory concentrations (MICs) were evaluated for the entire mushroom, the cap and the stipe, separately; the portion of the mushroom used proved to be influenced in the results obtained, which are directly correlated with the content of total phenols and flavonoids in the extracts. The growth of Grampositive bacteria (Bacillus cereus, B. subtilis,) was well inhibited by these mushrooms, while Escherichia coli (Gramnegative bacteria) was resistant. The study on the antifungal effect of these mushrooms revealed that Candida albicans and Cryptococcus neoformans were differently inhibited for the mushrooms used.
- Chemometric classification of several olive cultivars from Trás-os-Montes region (Northeast of Portugal) using artificial neural networksPublication . Peres, António M.; Baptista, Paula; Malheiro, Ricardo; Dias, L.G.; Bento, Albino; Pereira, J.A.This work aimed to use artificial neural networks for fruit classification according to olive cultivar, as a tool to guarantee varietal authenticity. So, 70 samples, each one containing, in general, 40 olives, belonging to the six most representative olive cultivars of Trás-os-Montes region (Cobrançosa, Cordovil, Madural, Negrinha de Freixo, Santulhana and Verdeal Transmontana) were collected in different groves and during four crop years. Five quantitative morphological parameters were evaluated for each fruit and endocarp, respectively. In total, ten biometrical parameters were used together with a multilayer perceptron artificial neural network allowing the implementation of a classification model. Its performance was compared with that obtained using linear discriminant analysis. The best results were obtained using artificial neural networks. In fact, the external validation procedure for linear discriminant analysis, using olive data from olive trees not included in the model development, showed an overall sensibility and specificity in the order of 70% and varying between 45 and 97% for the individual cultivars. On the other hand, the artificial neural network model was able to correctly classify the same unknown olives with a global sensibility and specificity around 75%, varying from 58 and 95% for each cultivar. The predictive results of the artificial neural network model selected was further confirmed since, in general, it correctly or incorrectly classified the unknown olive fruits in each one of the six cultivars studied with, respectively, higher and lower probabilities than those that could be expected by chance. The satisfactory results achieved, even when compared with previous published works, regarding olive cultivar's classification, show that the neural networks could be used by olive oil producers as a preventive and effective tool for avoiding adulterations of Protected Designation of Origin or monovarietal olive oils with olives of non-allowed cultivars.
- Bioactive properties of the medicinal mushroom Leucopaxillus giganteus mycelium obtained in the presence of different nitrogen sourcesPublication . Barros, Lillian; Baptista, Paula; Estevinho, Leticia M.; Ferreira, Isabel C.F.R.Leucopaxillus mushroom species are used in the chemical industry for extraction of clitocybin antibiotic and particularly the edible mushroom Leucopaxillus giganteus can be found in Northeast Portugal. Nevertheless, the production of its mycelium for pharmacological applications has not been explored. Herein, the mycelium obtained in the presence of four different nitrogen sources was investigated with regard to phenol production and antimicrobial and antioxidant properties. Phenol concentration increased along the growth time as a response to the oxidative stress and therefore free radical production. Although significant differences for mycelium growth between the nitrogen sources had not been observed, (NH4)2HPO4 proved to be the most appropriate to increase bioactive properties, leading to the highest phenol content and lowest EC50 and MIC values. The antimicrobial capacity was screened against Gram positive and Gram negative bacteria, and fungi. The samples selectively inhibited the growth of Gram positive bacteria, Staphylococcus aureus being the most susceptible one. Gram negative bacteria and fungi were resistant to the extracts. Antioxidant activity was calculated by the reducing power assay, the scavenging effect on DPPH radicals, and hemolysis and lipid peroxidation inhibition. Significantly negative linear regressions were established between phenols/flavonoids contents, which increased along the mycelia growth time and antioxidant activity.
- Controlo de infestantes em Horticultura em modo de produção biológico.Publication . Guilherme, Rosa; Baptista, Paula; Reboredo, Fernando; Pereira, J.A.Na produção de hortícolas em modo de produção biológico (MPB), o controlo das plantas infestantes é de grande dificuldade, limitando a produção devido à competição que exercem pela água e nutrientes. Neste sistema de produção a minimização dos prejuízos causados pelas infestantes, é conseguida normalmente pelo recurso a métodos culturais, físicos e mecânicos, onde é impedida a germinação, limitado o seu desenvolvimento, ou eliminação das infestantes através do arranque/corte/queima, colocação de barreiras ou mobilização do solo, este o mais usual. Neste sentido, no presente trabalho pretendem avaliar-se três técnicas para o controlo de infestantes, nomeadamente a monda térmica, a monda mecânica e a cobertura com tela, em comparação com a testemunha onde não se realizará qualquer intervenção. Para tal, num campo certificado em MPB na região do Baixo Mondego, será instalado um ensaio com as diferentes modalidades em estudo, em cultivo de três espécies hortícolas: couve crespa (Brassica oleraceae L.), alho francês (Allium porrum L.), ambas de cultivo habitual no outono-inverno e pimento (Capsicum annum L.) com um ciclo cultural característico de primaveraverão. O sistema de rega a utilizar é de gota a gota e todas as intervenções necessárias para o desenvolvimento das culturas como por exemplo as fertilizações e tratamentos fitossanitários, respeitam as normas de MPB. A avaliação das diferentes técnicas ocorrerá ao nível: I) do controlo de plantas infestantes; II) da biodiversidade e propriedades físicas e químicas do solo; III) e da produtividade, composição química e nutricional das três espécies cultivadas. Neste trabalho apresenta-se o desenho experimental, as metodologias que serão usadas para avaliação de cada um dos parâmetros e as principais metas que se pretendem alcançar.