CO-INOCULATION OF COMMON BEAN WITH PLANT GROWTH PROMOTER MICROORGANISMS

Co-inoculation with Rhizobium and plant growth promoter microorganisms (PGPMs) is can improve nodulation and plant growth; however, it is still necessary to study if there is synergistic interaction between microorganisms and effects of inoculants formulation. The aims were to evaluate the effects of co-inoculation of Rhizobium tropici (CIAT899=SEMIA 4077) + Azospirillum brasilense (ABV5+ABV6) (Rhi+Azo) and the PGPMs on nodulation and growth of common bean (Phaseolus vulgaris L.). The experiment was conducted on greenhouse using sandy soil and cultivar IPR Celeiro. The treatments were inoculation with Rhi+Azo and three PGPMs [Chlorella vulgaris (UTEX 396), Haematococcus pluvialis (UTEX 2505) and Arthrospira platensis (IPR7059)], two formulations (lyophilized or suspended cells in water) and three doses (50, 100 and 200 μL) using a 3x2x3 factorial scheme in a randomized complete block design with four replicates. Three treatments were included for comparison: the inoculant (Rhi+Azo), mineral N and a control without inoculation and without N mineral. Number and dry mass of nodule, shoot dry matter, N-ureide and N accumulated in the shoot dry matter of the common bean were evaluated at flowering. The indole-3-acetic acid (IAA) production in tryptophan-supplemented medium by microorganisms was also evaluated and it was found that the microalgae, C. vulgaris, H. pluvialis, and the cyanobacterium, A. platensis, were able to produce IAA. No statistical differences were observed between the cell formulations. These results show that the co-inoculation with PGPMs in common bean can be performed using lyophilized cell formulation as well as suspended cells in water. There was significant interaction between microalgae and doses. The highest dry shoot matter was observed to co-inoculation with C. vulgaris at the dose of 200 μL. Co-inoculation of Rhi+Azo and C. vulgaris has a synergistic effect and increases common bean development.