Exploitation of endophytes of centenarian olive trees in the management of olive knot disease

• Autor(a) principal: Moudjeber, Nawal
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10198/26285
• topic: Pseudomonas savastanoi pv.; Savastanoi; Bacterial community; Biological control; Incidence; Severity; Domínio/Área Científica::Ciências Agrárias::Biotecnologia Agrária e Alimentar

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.