Tese de mestrado, Biologia Evolutiva e do Desenvolvimento, Universidade de Lisboa, Faculdade de Ciências, 2020Interactions between microorganisms and plants have occurred for millions of years. Combining the capacity of light and CO2 usage by the plants with the capacity of efficient substrate usage by their microbiota, the water-to-land-transition was possible. Since then, plants and plant microbiota have coevolved, and today, the microbiome is considered as an extension of the plant’s genetic assembly. However, the agricultural revolution led to progressive alterations in habitat, crop managing practices, and breeding to promote crop production changing their evolutionary trajectory. Moreover, the trajectory of the co-evolution between crops and their microbiome is also changed. The soil, the plant, and the microorganisms are connected and impact each other. The rhizosphere is considered to be the most dynamic interface on Earth, and the microorganisms that exist there might promote plant growth and resilience. These microorganisms are referred to as Plant Growth-Promoting Microbes (PGPM), including Plant Growth-Promoting Rhizobacteria (PGPR) and Arbuscular Mycorrhizal Fungi (AMF). The experimental work is divided into three chapters according to the plant-model. In the first one, microorganisms (AMF and bacteria) were collected from a wild relative of chrysanthemum (Dendranthema grandiflora). Plant Growth Promoting Rhizobacteria (PGPR) was submitted for molecular analysis. Three of them (previously selected by plant growth-promoting traits) were inoculated on five chrysanthemum commercial cultivars to test their impact on plant performance and root microbiome assembly. AMF was also inoculated with the same propose. PGPR impacted the number of nodes and root biomass of commercial chrysanthemum cultivars. AMF affected the root biomass of cultivars of chrysanthemum cultivated in autoclaved and non-autoclaved soil. AMF root colonization was not found. All the treatments impacted the microbiome assembly in the tested commercial cultivars. Concluding, PGPR and AMF obtained from wild chrysanthemum impacted growth performance and microbiome assembly in five commercial cultivars. In the second one, AMF collected from wild chrysanthemum were proliferated using millet (Panicum miliaceum) as a host in order to have an inoculum of two morphotypes. The two morphotypes of AMF spores were successfully multiplied in millet roots and sorrowing soil. Millet appeared as a good host for the propagation of AMF spores. Lastly, in the third chapter, the same AMF were inoculated in sorghum (Sorghum bicolor) to test their impact on plant performance and resilience against Striga hermonthica, a parasitic weed. Sorghum growth performance and resilience were impacted by the presence of S. hermonthica and/or AMF in the soil. AMF root colonization on sorghum was observed and AMF treatments reduced S. hermonthica germination by 59%. However, the reduction of the germination of S. hermonthica seeds did not increase the sorghum growth performance, so more studies are needed to understand these mechanisms. Promising results were found, but additional work is needed to understand how these inocula are best applied in the field and the mechanisms behind it. It is also necessary to comprehend how the entire microbiome is affected by the inocula and how these changes impact growth performance and resilience in both, chrysanthemum, and sorghum species
