Screening of Rhizobacteria for their plant growth promotion abilities and their interaction with Rhizobium of Mung bean

Phosphorus deficiency is a major constraint for crop production. The beneficial microorganisms in the soil convert insoluble phosphorus into soluble form for plant growth and also prevents their leaching in to water bodies. In present investigation seventy two (72) rhizobacterial isolates were obtained from Mungbean rhizospheric soil on King’s B medium, from various locations near Jodhpur. All the isolates were screened for their ability to solubilize insoluble phosphate on Pikovskaya’s medium, nitrogen fixation and auxin like substance production. Four isolates were able to solubilize phosphate ranging from 42.69 ?g TCP/ml to 90.10 ?g TCP/ml. Total fifty eight (80.55%) isolates out of seventy two rhizobacteria were able to fix atmospheric nitrogen in vitro. Rhizobacterial isolates that were able to fix environmental nitrogen and solubilize phosphate were screened for auxin like substance production. Two isolates were able to produce auxin like substances at lower amount. Among all the rhizobacterial isolates screened for their influence on rhizobial growth in vitro, twenty three (31.94%) isolates stimulated the growth of Mung bean Rhizobium. The diameter of zone of stimulation varied from 6.0 mm (MrbIV 14) to 16.5 mm (MrbII 05 and MrbIII 16) and maximum stimulation was shown by MrbIII 10 (17.5 mm). However, thirty two (44.44%) isolates were neutral to the growth of Mung bean Rhizobium