Rhizobacterial promotion of maize growth and drought tolerance: perpectives from the laboratory, greenhouse and field

• Autor(a) principal: Santos, Beatriz Antunes
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/33355
• topic: Climate change; Plant growth promoting bacteria; Maize; Drought; BOX-PCR; Biochemical parameters

Due to climate changes, global temperature is projected to increase 1.5 °C or more. Consequentially, drought is expected to impact over 50% of the arable lands by 2050, affecting several crops, including maize, which is the third main food crop in the world. In fact, maize yield globally is expected to suffer a reduction of 15% because of drought stress. On the other hand, world population is predicted to reach 9 billion by 2050. Thus, there is the need to ensure food availability and security, to respond to an increased need to feed the growing population. In this context, rhizobacteria emerge as a more sustainable alternative or complement to chemical fertilizers. These bacteria exist naturally in the soil and are used to promote plant growth, and induce tolerance to abiotic factors, like drought, and are therefore called plant growth promoting rhizobacteria. Several strains have been applied in crops as biofertilizers, increasing productivity. Hence, this thesis aimed to explore the process of development of biofertilizers composed by plant growth promoting bacteria. To achieve that, maize plants were inoculated with rhizobacteria isolated from wild legumes, as well as with rhizobacteria isolated from maize plants and were grown in greenhouse under irrigated and drought conditions to screen for potential candidates to apply in the field. Posteriorly, in the field tests, maize yield was assessed to determine plant growth, and biochemical parameters were analyzed to understand how rhizobacteria inoculation improved maize development. Results evidenced maize growth and drought stress mitigation in the greenhouse, and biochemical parameters analyzed reveal the positive effect of bacterial inoculation, in the field. Additionally, rhizobacteria were isolated from maize plants growing under three levels of water deficit to understand if there would be any differences in their characteristics. Growth promotion abilities were evaluated as well as osmotolerance. In fact, microbial community associated with maize roots was affected by drought. Nevertheless, several strains were able to produce siderophores and bacteria isolated from conditions subject to water deficit had a lower osmotolerance. In general, the results of this thesis evidenced the potential of rhizobacteria to be applied in maize crops to mitigate drought stress and improve growth, ultimately increasing crop production.