Ameliorative effect of plant growth promoting bacterial endophyte Pantoea agglomerans on salt stress at early stage of growth in rice

Aims: Endophytes are known to impart tolerance to crop plants; hence the study was initiated to evaluate some plant growth promoting endophytic bacteria isolated from rice and maize for salt tolerance in rice. Methodology and results: A total of 31 endophytic bacteria were screened for growth promoting characteristics on the basis of phosphate solubilization, nitrogen fixation, Indole acetic acid biosynthesis, production of ammonium, protease and cellulase. Only 2 Bacillus species and Pantoea agglomerans were positive for all growth characteristics and subsequently inoculated with rice seeds under controlled as well as in saline condition (NaCl) in order to evaluate the plant growth promoting (PGP) ability on the basis of germination rate and seedling vigor. The seedling grown under control condition, significantly alter the growth parameters such as germination rate, root and shoot length, fresh and dry weight along with seedling vigor index. Under saline condition, the genus Bacillus and Pantoea invariably counteracted the effect of stress; however, P. agglomerans showed significant differences for shoot length, fresh and dry weight. Analysis of correlation coefficient exhibited positive and strong association of seedling vigor index with dry weight and rate of germination, thereby revealing the interdependency of the traits under stress. Conclusion, significance and impact of study: The study confirmed a mutualistic interaction of P. agglomerans with the host plant rice and leads to enhanced growth of the host under salt stress condition.