Indução de bactérias olubilizadoras de fosfatos em cultivo de feijão-caupi (Vigna unguiculata (L.) Walp.)

Abstract

Ecological relationship between microorganisms and plants is well known, however it is still under-explored. Thus, the aim of this research was to evaluate bacterial consortia as a growth inducers on cultivation of cowpea (Vigna unguiculata (L.) Walp.) by phosphate-solubilizing bacteria (PSB) of rizospheric soil of a cactus from Caatinga biome. Soil samples were analyzed and quantified to Cultivable Heterotrophic Bacteria (CHB) and PSB by Standard Plate Count (SPC) on Plate Count Agar (PCA) and Yeast Dextrose Agar (YDA), respectively. Twelve strains were isolated and submitted to Gram stain and Phosphate-Ferric (FePO4) solubilization capacity test. Antagonistic test by cross-streak technique was performed to assembly of bacterial consortia. Bacterial consortia was introduced on cultivation of cowpea, which was performed on vegetable house of Departamento de Fitotecnia, Universidade Federal do Ceará. After 45 cultivation days, the plants were evaluated to aerial portion length (APL), aerial portion dry mass (APDM), root dry mass (RDM) and total dry mass (TDM). The substrate was evaluated to labile P content. Variables were submitted to statistical tests. CHB and PSB counts showed values of 4.62×107 and 3.475×107 CFU/g, respectively. About 82% of strains were Gramnegative and 18% were Gram-positive. Of the 12 strains capable to solubilize CaHPO4 seven were capable to solubilize FePO4. From the antagonism test were elected four bacterial consortia which were induced on cowpea cultivation. According to statistical tests, C4 consortia was more efficient by BDM and TDM accumulation. From the labile P substrate accumulation analysis, C3 and C4 consortia were showed best efficiency to this process. Therefore, it was possible to verify that the treatments with higher TDM averages were also those with higher labile P content in the substrate.