Prospecção de rizobactérias com atividades promotoras de crescimento do feijoeiro comum

Abstract

Bean (Phaseolus vulgaris L.) is a very consumed legume in the world and its cultivation is one of the most important activities in the Brazilian economy. Bean productivity can be affected by soil mineral deficiency and by pathogen and insect attack. The objective of this work was characterize physiologically isolated of plant growth promoting rhizobacteria and investigate the potential of rhizobacteria solubilizing phosphate in the development of common bean in greenhouse. For the physiological characterization, were used 86 isolates from Prata-anã banana roots collected in the northern region of the State of Minas Gerais. All isolates were submitted to biochemical activity evaluations, according to established protocols, for phosphate solubilization, indole-3-acetic acid production, biological nitrogen fixation, siderophores production and production of lipase, protease and chitinase enzymes. Nine phosphate solubilizers were taken into greenhouse to evaluate the performance of common bean in response to the microbiolization of the seeds with rhizobacteria. The experiment was carried out in a randomized complete block design, with 6 replicates, in a 9x2 + 2 factorial scheme, nine of which were rhizobacteria isolates and two phosphorus sources (Gafsa and Super Simple Natural Phosphate). The additional treatments consisted of two sources of phosphorus without bacteria. The data obtained for the in vitro experiment were submitted to analysis of variance and, when significant, to the Scott and Knott test, at 5% probability, for comparison of the means. The agronomic attributes data of the bean were submitted to analysis of variance in factorial escheme and, when significant, to the Scott and Knott test, at 5% probability, for comparison of the means. Treatments were compared with the additional treatment by the Dunnet test at 5% probability. The evaluated rhizobacteria presented potential for the solubilization of inorganic tribasic calcium phosphate, besides being able to produce the acid phosphatase. In contrast, all the isolates evaluated for solubilization of aluminum phosphate and iron phosphate were negative.Of the 86 isolates investigated, 54.6% formed characteristic solubilization halo for inorganic tribasic calcium phosphate, 7% were EIA producers, only when submitted to the Tryptophan path, 27.9% were siderophore producers, and 47.7% were lipase producers. All the isolates evaluated in this work were negative for nitrogen fixation activity, besides not producing protease and chitinase. The rhizobacteria promoted increase in biomass for the evaluated attributes. It is concluded that the rhizobacteria evaluated are phosphate solubilizers, producing AIA and siderophores, as well as lipase enzyme producers. The evaluated rhizobacteria increase the agronomic attributes evaluated.Of the 86 isolates investigated, 54.6% formed characteristic solubilization halo for inorganic tribasic calcium phosphate, 7% were AIA producers, only when submitted to the Tryptophan path, 27.9% were siderophore producers, and 47.7% were lipase producers. All the isolates evaluated in this work were negative for nitrogen fixation activity, besides not producing protease and chitinase. The rhizobacteria promoted increase in biomass for the evaluated attributes. It is concluded that the rhizobacteria evaluated are phosphate solubilizers, producing AIA and siderophores, as well as lipase enzyme producers. The evaluated rhizobacteria increase the agronomic attributes evaluated.