IN VITRO COLONIZATION OF SORGHUM ROOTS BY RHIZOBACTERIA

Abstract

The incorporation of growth promoting rhizobacteria to the production systems has become a promising strategy to minimize limiting factors in crops, such as water stress and phytosanitary problems. Therefore, this work aimed to evaluate the in vitro colonization of sorghum roots by rhizobacteria through seed microbiolization methods. The work was conducted in the laboratory, in the Agricultural Sciences Complex - ASC of the State University of Tocantins, Palmas - TO. An entirely randomized design was used, in a factorial scheme (2x5), with two microbiolization methods and five treatments, with four repetitions.  The microbiolization methods were seeds without pre-germination and pre-germinated seeds. The treatments were commercial products based on rhizobacteria: Azospirillum brasilense, strains AbV5 and AbV6 (UFPR) (Azokop®); Bacillus methylotrophicus UFPEDA 20 (Onix®); Bacillus subtilis UFPEDA 764 (Rizos®); Bacillus megaterium + Bacillus subtilis (BiomaPhos®) and control (distilled water). The evaluation of root colonization was performed visually, considering that the presence of a cloudy and whitish haze along and around the root indicated colonization by rhizobacteria. The germination percentage and the length of the aerial part and root were also evaluated. Seeds inoculated with commercial products based on Bacillus methylotrophicus and the combination of Bacillus megaterium + Bacillus subtilis showed a higher percentage in relation to root colonization and germination of sorghum seeds, when compared to commercial products based on Azospirillum brasilense, Bacillus subtilis and the control. There was no significant difference for the variable aboveground height, between the analyzed means in the treatments and methods used. For root length, there was no significant difference between treatments, but there was a difference between the methods. The results obtained in this study showed that the use of commercial products based on rhizobacteria in sorghum seeds has the potential to be used in future studies, aiming to promote the use of rhizobacteria in promoting the growth of this grass.