Potencial de rizobactérias para a promoção de crescimento vegetal

Abstract

Rhizosphere, the zone of soil under direct influence of the roots, sustains an abundant proliferation of microorganisms, which act directly on the plants in a beneficial way or otherwise. Such microorganisms might present an important influence on agricultural productivity. Among the microorganisms inhabiting this zone are the plant growth-promoting rhizobacteria (PGPRs). They are able to colonize the root system of plants, benefiting them through different mechanisms. Hence, this work aimed to evaluate rhizobacteria (named RD06, RD10, RD12, RD27, RD34 and SD18), previously isolated from bean rhizosphere, regarding their plant growth-promoting traits. Therefore, the bacterial potential for root colonization, the ability to produce phytohormones (gibberellin, cytokinin, indole acetic acid), asymbiotic nitrogen fixation, and inorganic phosphate solubilization, were evaluated. The results showed that all of the evaluated isolates had the ability to colonize the bean rhizosphere. As for phytohormones, gibberellin production was observed for isolates RD10 and RD27. Results for the RD27 and RD34 isolates suggest their ability to produce cytokinins. As for indole acetic acid, none of the bacterial isolates was demonstrated to produce this phytohormone through the methods employed. A similar result was observed for the solubilization of inorganic phosphate, where none of the isolates displayed this feature. All bacterial isolates presented the ability to grow on nitrogen-free solid and semi-solid media, indicating the potential capacity for atmospheric nitrogen fixation. In general, the rhizobacteria have demonstrated different mechanisms that point to the potential of plant growth promoting.