Loquat (Eriobotrya Japonica) microbiota : screening of potential biocontrol agents against Erwinia amylovora

• Autor(a) principal: Azevedo, Telma Maria Sampaio
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/20.500.11960/1869
• topic: Erwinia amylovora; Microbiota; Fire blight; Pathogen; Bactéria; Enterobacter cancerogenus; Curtobacterium flaccumfaciens; Rosenbergiella epipactidis; Pseudomonas; Rhizosphaerae

Fire blight, caused by the bacterium Erwinia amylovora, is one of the most destructive diseases that affect crops of the Rosaceae family, representing a serious threat to orchards and ornamental species of a great economic interest. Due to its pathogenicity, E. amylovora is considered a quarantine organism in the European Union. Portugal is, since 2008, recognized as a “Protected Area” for this bacterium. The lack of available efficient phytochemicals and antibiotics, as well as their high toxicity and resistance, have led to the innumerous research work to screen for new organisms with a biological control action. Nowadays biological control active ingredients are already present in some commercialized products, used as a preventive measure against E. amylovora. However, further studies are necessary in investigating new strains or species with biopesticide action for specific crops. The main objective of this work was to select for possible antagonists against E. amylovora from microbiota obtained from loquat (Eriobotrya japonica) flowers and leaves. For this reason, distinct isolation methodologies, characterization and ex vivo assays were performed in fruits and flowers in order to evaluate the efficacy of the strains in study on delaying the onset of symptoms caused by pathogen infection, as well as the incidence and severity of this infection. Out of the 173 bacterial isolates studied, 4 species (Rosenbergiella epipactidis, Pseudomonas rhizosphaerae, Curtobacterium flaccumfaciens and Enterobacter cancerogenus) were selected since they delayed the onset of fruit necrosis, being associated with low levels of incidence and severity of disease infection (high efficacy of antagonistic activity), as well as no pathogenicity. Since flower stigmas are the more appropriate organs to E. amylovora colonization and development, two flower bioassays were conducted to assess the antagonistic activity of these bacterial species: in complete flowers (R. epipactidis, P. rhizosphaerae, C. flaccumfaciens and E. cancerogenus) and in flowers only with hypanthium and peduncle (R. epipactidis and P. rhizosphaerae). The molecular analysis by real-time PCR to quantify E. amylovora concentrations after treating the flowers with a selected bacterial antagonistic species did not show a relationship between the E. amylovora concentration and the observed symptoms in both flower bioassays.