Caracterização bioquímica de bactérias isoladas das raízes de arroz de sequeiro quanto a produção de biocompostos e promoção do crescimento vegetal

Abstract

Improve soil fertility and crop productivity, reducing the negative impact of chemical fertilizers on the environment is something essential for modern agriculture. In this context it has been observed a constant interest in the study of soil microorganisms, which contribute to agricultural activity, especially improving soil fertility and for a sustainable agriculture. The process of biological nitrogen fixation allows that different microorganisms supplement totally or partially the nitrogen demand of the host plant. This study aimed to analyze parameters that can indicate the efficacy of bacterial isolates from root nodules of sequeiro rice plants, in relation their efficiency in the production of biocompounds and plant growth promotion. Were evaluated parameters as growth cellular profile, production of total proteins, biofilm formation with the determination of biomass and cell viability, production of auxin (indole-3-acetic acid), molecular analysis of intergenic spacer region 16S-23S and germination test with the cultivars Canastra and Caiapó. The behavior of the strains were different in the three culture mediuns. The growth profile and production of total proteins were greater in potato broth than another mediuns from 12 and 36 hours of incubation, respectively. All strains formed biofilm with viable cells associated, with levels depending on the medium and the strain in question. Was observed that the potato broth provide a better formation of the biofilm with associated biomass, however when the ratio between biomass and growth rate is considered the biofilm index was higher for RDM and YM medium. All isolates produced AIA, with values variation from 0.207 μg.mL-1 to 33.212 μg.mL-1. In molecular characterization by amplification of the spacer intergenic region 16S-23S were observed that PCR products fragments ranging from 787-9045 base pairs (bp) with presence of 1 to 3 separate bands in agarose gel, thus, it allowed share the strains into nine groups with 100% similarity, with group II compound for nine strains. In germination test, the Canastra genotype was better than Caiapó in relation of the number of ramifications, fresh mass for root and shoots and dry mass for root. Caiapó was better than Canastra only for dry mass of shoots. In the overall assessment by treatment, significant differences were observed only for root and shoot, and the isolated R5 showed the best results in these two parameters.