Amenização do estresse salino em milho inoculado com bactérias promotoras de crescimento de plantas e fungo micorrízico arbuscular

Abstract

Corn (Zea mays L.) is one of the most consumed grains in the world, and in addition to being used for human and animal food, it stands out in the energy matrix industry. Faced with the degradation and salinization of soils, it is necessary to search for sustainable technologies that help the adaptation and tolerance of corn and other plants of economic interest to the vast limiting edaphoclimatic conditions. In view of the limiting problems of saline soil, this research aimed to study the behavior of 24 plant growth-promoting bacteria (PGPB) strains, isolated from a temporary semi-arid pond, in reducing damage caused by saline stress, benefiting the agronomic performance of the plants. corn plants and favoring the tripartite symbiotic association between the arbuscular mycorrhizal fungus (AMF) (Rhizophagus clarus) and the corn plant (IPA CMS 36). For this, the PGPB were tested in a halophilic medium to confirm their salinity tolerance potential, selecting the 10 isolates that presented the best performance. Subsequently, an experiment was carried out in an autoclaved substrate in a greenhouse for 60 days in order to verify the potential for promoting growth in vivo, as well as the levels of leaf photosynthetic pigments and parameters of chlorophyll a fluorescence emission (Initial Fluorescence [F0]; Variable fluorescence [Fv]; Maximum fluorescence [Fm]; PSII electron flux [Fv/Fm]; Quantum efficiency per reaction center [Et0/CR]) of bacteria selected from the halotolerance test at different saline concentrations (0, 40, 80 mM). From this experiment, bacteria 28-7 were selected; 43; 46-1; 70; and 79-1, which showed higher biometric parameters and bacteria 24-1; 46-1; 52; and 70, which showed the best performance of photosynthetic parameters. Bacteria 28-7; 43; 46-1; 70; and 79-1 were used in a second experiment lasting 49 days, following the same pattern as the first experiment and submitting the treatments to different saline concentrations (0, 40, 80 mM). In this experiment, the co-inoculation of Rhizophagus clarus was carried out in order to evaluate the plant biomass, the levels of nutrients accumulated in the plant tissue and the rate of colonization of the roots by AMF. The greatest increase in biomass was observed for bacteria 41-6; 70 and; 79-1 in consortium with the fungus. For nutrient contents, the results suggest a greater tolerance of corn plants to salt stress through osmoregulation mediated by microorganisms provided by bacteria 28-7; 46-1; 70; 79-1 co- inoculated with the fungus R. clarus. The results achieved by this research accept the initial hypothesis raised that PGPB help to alleviate the symptoms caused by saline stress and favor the symbiosis between plant-fungus, establishing a tripartite synergy relationship between plant-fungus and bacteria. Thus, it highlights the biotechnological potential of microorganisms for the bioprotection and biofertilization of plants in soils affected by salts.