CARACTERÍSTICAS MULTIFUNCIONAIS DE RIZOBACTÉRIAS ISOLADAS DE PLANTAS DE SOJA COM POTENCIAL PARA PROMOÇÃO DO CRESCIMENTO VEGETAL

Abstract

Soybean cultivation occupies an important space in Brazilian production and requires a large input of nitrogen and phosphorus, in addition to suffering from the attack of phytopathogens. The objective of this work was to select rhizospheric bacteria from soybean genotypes cultivated in Cerrado soils, with potential to promote plant growth. Ten bacterial isolates were evaluated for their in vitro capacity for phosphate solubilization, nitrogen fixation and antibiosis to the fungus Sclerotinia sclerotiorum. In the inorganic P solubilization, the cultures had their OD standardized, were diluted and inoculated in triplicate in the GL medium supplemented, separately, with two phosphate sources of calcium and iron, then submitted to the colorimetric method and the pH of the culture medium was measured, and their results estimated by the standard curve equation. Nitrogen fixation was qualitatively evaluated and considered positive when the isolates inoculated in NFb medium presented a thin film in the form of a veil. The antagonist activity was evaluated by the double culture technique where the diameter of the mycelium was measured to determine the percentage of inhibition of fungal growth in the presence of the bacteria, calculated through the relative inhibition index. Among the 10 isolates, BRC11, SAC36, SAF09 and SAF11 stood out, which showed characteristics of plant growth promotion such as potential for solubilization of calcium and iron phosphates, nitrogen fixation, antagonism to the fungus S. sclerotiorum, thus representing a strategic alternative for sustainable intensification of agricultural systems.