Tratamento de sementes com microrganismos benéficos: vigor e respostas fisiológicas de plântulas

Abstract

Modern agriculture requires technologies capable of enhancing the productive efficiency and sustainability of agricultural systems while reducing reliance on chemical inputs. In this context, the use of beneficial microorganisms for seed treatment represents a promising strategy to directly influence germination, vigor, and early plant establishment. This thesis integrates studies on bio-inputs, bacteria, osmoprotective solutions, the isolation and characterization of the biotechnological potential of mixed microbial cultures, and the induction of systemic resistance, with an emphasis on utilizing microbial resources and developing technologies applicable to regional agricultural conditions. Chapter 1 details the development of a technological solution for treating stored soybean seeds, combining microorganisms with an osmoprotective matrix to improve seedling vigor. Various imbibition periods and microbial treatments were tested, revealing that the response depends on the formulation's composition and application conditions. The treatment promoted early growth characteristics and vigor in soybean seedlings, highlighting the potential for developing formulations for biological seed treatment. Chapter 2 evaluates the biopriming of maize seeds with Bacillus amyloliquefaciens, assessing germination, seedling morphology, and the activity of antioxidant enzymes— specifically superoxide dismutase, ascorbate peroxidase, and catalase. While germination rates remained unchanged, exposure time proved crucial for seedling vigor, growth, and antioxidant metabolism. A four-hour exposure yielded positive responses, whereas six hours of exposure was associated with reduced vigor and increased ascorbate peroxidase activity, reflecting a higher antioxidant demand. These chapters demonstrate that contact time is a decisive variable; appropriate durations foster balanced physiological responses, whereas prolonged exposure can alter metabolism and compromise vigor. In Chapter 3, mixed microbial cultures were screened, and their biotechnological potential was evaluated regarding inorganic phosphorus solubilization, *in vitro* antagonism against the fungus Macrophomina phaseolina, and germination in bean and soybean crops. In Chapter 4, a systematic review gathered evidence on systemic resistance induced by beneficial microorganisms. Trichoderma, Bacillus, and Pseudomonas stood out as key genera involved in activating plant defenses, a process mediated by genes, proteins, enzymes, reactive oxygen species, and hormonal pathways linked to jasmonic acid, salicylic acid, and ethylene. Collectively, these studies provide insights into the efficiency of bio-inputs and highlight how performance depends on the interplay between the microorganism, formulation, plant species, application timing, and environmental conditions. Overall, the results reinforce the potential of the evaluated bio-inputs but also demonstrate the need for further research into stability, compatibility, microbial survival, and agronomic validation across different production conditions.