PHOSPHATE-SOLUBILIZING BACTERIAL CO-INOCULA AND THEIR EFFECT ON GERMINATION AND PLANT GROWTH OF COMMON BEAN

The effect of three phosphate-solubilizing bacterial co-inocula (PSB) on in vitro germination, growth and development of common bean plants (Phaseolus vulgaris L.) and on soil phosphorus bioavailability under semi-controlled conditions was evaluated. In order to determine the effect on in vitro germination, we used three PSB (PSB1: Enterobacter sp. + Burkholderia gladioli; PSB2: Enterobacter sp. + Pseudomonas luteola and PSB3: P. luteola + Aeromonas hydrophila) and two controls, sterile saline solution (SSE) and sterile distilled water, combined with three times of seeds imbibition: 30, 60 and 120min. To evaluate the effect of each PSB co-inoculum on the plant growth and development of common bean plants, as well as on the soil phosphorus bio-availability four seeds were planted in pots with non-sterile soil in which four treatments were applied (PSB1, PSB2, PSB3 and control without inoculation). With respect to the control (SSE), the seeds dipped in the PSB3 during 120 min presented the greatest length of radicle and vigor index. The weight of 100 seeds of the plants under semi-controlled conditions increased 3.5 and 4.6% with PSB2 and PSB3, respectively, as compared to the control. The lowest soil pH value and the highest available-P content were found with the PSB2. PSB2 and PSB3 seem to favor germination and some biometric parameters of common beans; however, evaluation for more than one crop cycle is suggested to confirm the positive effects of these PSB co-inocula.