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Projeto de investigação
Innovative tools to combat crop pests in the Mediterranean
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Exogenous systemin peptide treatment in olive alters Bactrocera oleae oviposition preference
Publication . Sánchez, Luiza; Cunha, Ana E.; Rodrigues, Nuno; Pereira, José Alberto; Baptista, Paula
The 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.
Potential of the endophyte Penicillium commune in the control of olive anthracnose via induction of antifungal volatiles in host plant
Publication . Silva, Sofia; Costa, Helgeneusa Neto da; Lopes, Teresa; Ramos, Vitor; Rodrigues, Nuno; Pereira, J.A.; Lino-Neto, Teresa; Baptista, Paula
Olive anthracnose, caused by several Colletotrichum species, is the most economically harmful fruit disease of the
olive crop. This work aimed to evaluate the ability of the endophyte Penicillium commune CIMO 14FM009 to
protect the olive tree against Colletotrichum nymphaeae via induction of plant volatile organic compounds (VOCs).
Accordingly, olive tree branches were inoculated with the endophyte and one month later with the pathogen.
After 0, 3, and 24 h of pathogen inoculation, the volatile composition of leaves and fruits was analyzed by HSSPME-
GC/MS, and compared with controls (branches inoculated with buffer, endophyte, or pathogen). The
effect of plant-derived volatiles on C. nymphaeae was also evaluated. Penicillium commune induced the release of
VOCs on the olive trees, with the capacity to reduce significantly the growth (up to 1.4-fold) and sporulation (up
to 1.2-fold) of C. nymphaeae. This effect was most notorious on olives than on leaves, and occurred 3 h after
pathogen-challenge, suggesting the need for a stressful stimulus for the production of antifungal VOCs. The
observed inhibition was associated to a specific set of VOCs released from olives (mostly belonging to the alcohols
and esters chemical classes) and leaves (mostly belonging to the alkenes). Curiously, a set of VOCs
belonging to alkene, alkane and ester classes, were emitted exclusively in olive branches inoculated with
C. nymphaeae. These findings provide new possibilities for controlling olive anthracnose using P. commune and/or
volatiles, which efficacy should be tested in future works.
Exploitation of endophytes of centenarian olive trees in the management of olive knot disease
Publication . Moudjeber, Nawal; Baptista, Paula
Endophytes are microorganisms that spend most of their life cycle within plant tissues and they are recognized to play important roles in plant protection against abiotic and biotic stresses. Some recent studies have been showed that ancient plants are inhabited by a greater number of rare endophytes and may represent a rich repository of potential biocontrol agents. Thus, in this work the effect of the application of a consortium of bacterial endophytes, retrieved from centennial olive trees, on the development of olive knot (OK) disease, was evaluated. The mechanisms responsible for the control of OK by this consortium of microorganisms was also evaluated by studying the changes in the indigenous stem endophytic bacterial community, through 16S rRNA gene amplicon-based metagenomic analysis. Accordingly, endophytes were extracted from stems of centennial olive trees using a Histodenz gradient, and used to inoculated one-year-old olive plantlets. One week later, these plants were inoculated with the causal agent of OK, the bacterium Pseudomonas savastanoi pv. savastanoi (Pss). Results showed that the inoculation with bacterial endophytes reduced significantly both the incidence (up to 1.6-fold) and severity (up to 2.1-fold) of OK, when compared to plants inoculated exclusively with the pathogen Pss. This effect is likely due to changes caused by bacterial endophytes on stem associated-bacteria composition, being noticed a decrease on Pseudomonas, Methylobacterium and Mycoplasma and an increase on Micrococcaceae, Rikenellaceae and Corynebacterium, when compared to plants inoculated uniquely by Pss. Likewise, the inoculation of plants uniquely with Pss affected greatly the bacterial community assembly of the stem and potentially beneficial bacteria. The bacterial inoculum was dominated by the symbiotic genus Mycoplasma, being the first time reported on olive tree. Overall, the results suggest that centenary olive trees may represent an important source of endophytes with valuable biocontrol proprieties. The inoculation of olive plants with endophytes from ancient trees could be an innovative strategy to manage olive knot disease. Despite these promising results, further studies are needed to better understand their mechanisms of action.
Identificação de bacteriófagos com potencial no controlo da tuberculose da oliveira
Publication . Costa, Maíra; Baptista, Paula; Cameirão, Cristina Sofia Lopes; Nava, Gilmar Antônio
Pseudomonas savastanoi pv. savastanoi (Pss) é a bactéria patogénica causal da doença tuberculose-da-oliveira, sendo uma das principais responsáveis pelas perdas significativas na produção e qualidade do olival em todo o mundo especialmente em países do Mediterrâneo. O seu ataque na oliveira ocorre na parte aérea, formando nódulos visíveis no tronco, caule, folhas e frutos, não existindo um tratamento específico e eficaz quando estabelecida no olival. Ocasionando a necessidade no desenvolvimento de ferramentas inovadoras, seguras e eficazes para o seu controlo. Assim, neste trabalho pretendeu-se identificar bacteriófagos com potencial de serem usados contra a tuberculose. Devido à elevada especificidade dos fagos, procedeu-se numa primeira fase ao estudo da comunidade bacteriana endofítica associada a tumores e a ramos de oliveira sem sintomas com o intuito de constituir uma coleção de estirpes de Pss que será útil no processo de seleção de bacteriófagos. O isolamento em cultura seguida pela identificação dos isolados bacterianos através da sequenciação da região 16S do rDNA permitiu identificar um total de 69 taxa, sendo Pantoea e Erwinia os géneros mais abundantes em caules assintomáticos, tendo destaque nos sintomáticos os géneros Pantoea e Curtobacterium. O método por maceração gerou uma maior diversidade taxonómica que no método de explante, sendo nos caules sintomáticos que verificou maior diversidade e abundância bacteriana relativamente aos caules assintomáticos. O isolamento de bacteriófagos em amostras de solo de olival permitiu identificar, pela primeira vez, um total de nove bacteriófagos com capacidade de causar a lise de Pss. A sua ação na luta contra a tuberculose deverá ser avaliada no futuro com ensaios in planta. Quando avaliada a eficiência dos bacteriófagos contra a Pss em fatias de cenoura biológica, não se obteve diferenças significativas, no entanto os resultados obtidos sugerem que os bacteriófagos podem ser considerados possíveis agentes de biocontrolo contra a multiplicação do patógeno, necessitando, porém, de estudos complementares.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
PRIMA Section 2 - Multi-topic 2018
Número da atribuição
PRIMA/0002/2018