Plant growth promotion of radish by rhizosphere dwelling bacteria

The present study was carried out with the aim to develop a plant growth-promoting rhizobacterial inoculant for improving the growth of radish. A total of 20 rhizobacteria were isolated and then tested for multifarious plant growth-promoting traits. The isolates exhibited tricalcium phosphate and zinc solubilization, production of siderophores, auxins, ammonia and growth on different nitrogen free medium. Out of 20 isolates, two potential bacterial isolates (RM3 and RL3) were selected on the basis of PGP traits for evaluation of their potential to promote growth of radish under pot conditions. In green house experiment, these isolates when used as consortium showed a significant improvement in soil enzymatic activities (viz. dehydrogenase: 12.99 µg TPF formed h-1 g of soil-1, alkaline phosphatase: 11.94 µg PNP formed h-1 g of soil-1 and urease: 401.65 µg urea hydrolyzed formed h-1g of soil-1) and plant growth parameters (shoot length: 38.76 cm, leaf area: 267cm2, fresh leaf weight:106.05 g, dry leaf weight:1.23 g, number of leaves per plant: 23, fresh root weight:111.69 g, dry root weight: 2.06 g, root length: 34.04 cm and root diameter: 3.33 cm) relative to control as well as other bioinoculants. These bacteria were tentatively identified as Bacillus (RM3) and Pseudomonas (RL3) on the basis of biochemical tests.