AN ASSESSMENT OF P LANT G ROWTH P ROMOTING RHIZOBACTERIAL STRAINS FOR GROWTH OF SPINACI A OLERACEA U NDER I N - VIVO CONDITIONS

Plant growth promoting rhizobacteria (PGPR) are beneficial bacterial strains found in rhizosphere that colonize plant roots and enhances plant growth by wide mode of mechanisms. T he usage of PGPR is increasing day by day in the fiel d of agriculture and it offers a sensible way to replace ch emical fertilizers, pesticides and other supplements. This preliminary study was carried - out to evaluate nine rhizobacterial strains associated with Spinaci a o leracea for different plant growth parameters i.e. root length, shoot length, number of leaves an d area of leaves , under i n - vivo conditions. The tested rhizobacterial strains were isolated in a previous study from soil that had been cultivated with Spinaci a oleracea for at least three consecutive seasons. This study is further extension of our work which involved the in - vitro analysis of the rhizobacterial strains for different plant growth promoting activities . A ll the tested rhizobacteria l strains showed positive p erformance in terms of improvement in plant growth parameters when comp ared to that of control . Strains R13, R40, R50, and R53 showed best plant growth parameters under i n - vivo conditions . Furthermore upon completion of one month, t he shoot length of plants inoculated wit h isolate R13, R40, R50, R53 were found to be 32cm, 26.5cm, 34 cm, 38.6cm respectively, compared to control i.e. 21 cm, whereas root length of plants inoculated with same isolates were found to be 8cm, 15cm, 12.5cm, 8cm respectively, c ompared to control i.e. 9.5 cm. Number of leaves per plant , which were inoculated with these respective strains were found to be 8 units, 6 units, 8 units, and 7 units respectively, compared to control i.e. 6 units, and leaf area of these plants which were inoculated with same isolates were found to be 20cm 2 , 18.15cm 2 , 20.07cm 2 , and 13cm 2 respectively, compared to control i.e. 19.68 cm 2 . These results suggest that isolate R13, R40, R50, R53 may be tested further for more plant growth promoting traits eventually developing it as potential soil inoculants in order to enhance the growth of Spinacia oleracea `