Uso de Bacillus aryabhattai na cultura do milho: tolerância à seca, aspectos fisiológicos e produtividade

Abstract

Climate change has intensified the frequency and severity of drought periods, affecting maize (Zea mays L.) production. In this context, the use of plant growth-promoting rhizobacteria (PGPR) has emerged as a sustainable biotechnological alternative to mitigate water deficit stress. Among PGPR, Bacillus aryabhattai, strain CMAA 1363, originally isolated from the roots of Cereus jamacaru, a cactus native to the Caatinga biome, promoted drought tolerance and growth in several crops. This dissertation, divided into three articles, characterizes the role of B. aryabhattai, strain CMAA 1363 in mitigating water deficit stress and promoting growth in maize plants. In Article 1, the impact of inoculation under well-watered and water-deficient conditions was evaluated in a pot experiment conducted under controlled greenhouse conditions. Inoculation alleviated the effects of water deficit by increasing relative water content (RWC) and the activity of the antioxidant enzymes superoxide dismutase, catalase, and ascorbate peroxidase, reducing electrolyte leakage (EL) and proline content, and protecting the photosynthetic apparatus, as evidenced by the preservation of chlorophylls and improvements in the oxygen-evolving complex (OEC), reaction center/absorption ratio (RC/ABS), performance indices (PIabs and PIcs), and absorption-based driving force (DFabs). Under wellwatered conditions, inoculation also promoted beneficial changes in OEC, RC/ABS, PIabs, PIcs, DFabs, and energy fluxes per cross-section. In both water regimes, improvements in morpho-agronomic parameters were observed, particularly increased root dry mass. In Article 2, the objective of the experiment was to mitigate water deficit stress during the vegetative stage of maize through inoculation with B. aryabhattai strain CMAA 1363, aiming to understand its subsequent effects on crop productivity after stress exposure. In this field experiment, the PGPR also promoted higher RWC and antioxidant activity of CAT and APX, reduced EL and proline content, and protected the photosynthetic apparatus, which was reflected in improved morphoagronomic parameters and increased productivity. Finally, in Article 3, the effect of inoculation on maize plants during the reproductive stage was evaluated. In this experiment, inoculation increased RWC, reduced EL, and protected the photosynthetic apparatus under water deficit stress; however, these beneficial ecophysiological changes were not reflected in increased productivity. In well-watered conditions, the effect was even more pronounced, with higher chlorophyll indices and photochemical efficiency, yet without greater productivity. Therefore, inoculation with B. aryabhattai strain CMAA 1363 represents a promising strategy for promoting growth and drought tolerance in maize plants, particularly during the vegetative stage of the crop.