Co-inoculation of endophytic bacteria and rhizobia for improving growth of mung bean (Vigna radiata L.) under axenic conditions

Performance of plant growth promoting soil bacteria often give inconsistent results due to variable conditions of soil and environment. Plant growth promoting endophytic bacteria may give better response in crop production because they colonize within plant tissues and remain protected from outside environmental conditions. In this study, endophytic bacteria were isolated from wheat and maize crop and in vitro biochemical characteristics such as ACC-deaminase activity, ammonia production, exopolysaccharide production, siderophore production, phosphate solublization, Zn solubilization and auxin production was determined. To identify growth promoting strains. After characterization, the five efficient strains were selected. The results revealed that 33% of endophytic isolates were able to produce ACC-deaminase, 40% produced ammonia, 37% were able to produce exopolysaccharides, 40% produced siderophore, 31 and 77% able to solubilize phosphate and zinc respectively. All strains were able to produce auxin with and without L-TRP under normal 100mM salt and 15% drought conditions. Pre-isolated rhizobial strains (M9 and M6) were taken from Soil Microbiology and Biochemistry Lab of Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad. The effect of co-inoculation of endophytic and rhizobial strains on growth of mung bean was compared with sole inoculation of efficient strains of endophytic bacteria and pre-isolated rhizobial strains in glass jars under axenic conditions. The experiment was conducted by following completely randomized design (CRD) with three replications. After 25 days, crop was harvested and data regarding growth parameters was recorded. Data revealed that co-inoculation showed significant improvement in growth as compared to sole inoculation of rhizobial strains. Among all endophytic strains, E25 and E19 showed significant increase in growth parameters than rhizobial strains. Moreover, effect of inoculation with endophytic and rhizobial strains was significant over control.