Plant growth‐promoting endophytic bacteria augment growth and salinity tolerance in rice plants

• Published in: Plant biology (Stuttgart, Germany) Germany), 2020-09, Vol.22 (5), p.850-862
• Main Authors: Khan, M. A., Asaf, S., Khan, A. L., Adhikari, A., Jan, R., Ali, S., Imran, M., Kim, K.‐M., Lee, I.‐J., Papen, H.
• Format: Article
• Language: English
• Subjects: Abiotic stress; Abscisic acid; Acetic acid; Actinobacteria - physiology; Aquatic plants; Bacteria; Bacterial endophytes; Bacterial Physiological Phenomena; Dunes; Efflux; Endophytes; Endophytes - physiology; Enterobacter - physiology; Flavin; gene expression; Gibberellins; Indoleacetic acid; Inoculation; Micrococcus - physiology; Monooxygenase; Organic acids; Oryza - microbiology; phytohormones; Plant growth; Plant hormones; Plant Roots - microbiology; Rice; rice plant; Salinity; Salinity effects; salinity stress; Salinity tolerance; Salt Tolerance - physiology; Salts; Seedlings; Side effects; Sodium chloride; Strains (organisms)
• ISSN: 1435-8603; 1438-8677
• DOI: 10.1111/plb.13124

Salt stress negatively affects growth and development of plants. However, it is hypothesized that plant growth‐promoting endophytic bacteria can greatly alleviate the adverse effects of salinity and can promote growth and development of plants. In the present research, we aimed to isolate endophytic bacteria from halotolerant plants and evaluate their capacity for promoting crop plant growth. The bacterial endophytes were isolated from selected plants inhabiting sand dunes at Pohang beach, screened for plant growth‐promoting traits and applied to rice seedlings under salt stress (NaCl; 150 mm). Out of 59 endophytic bacterial isolates, only six isolates, i.e. Curtobacterium oceanosedimentum SAK1, Curtobacterium luteum SAK2, Enterobacter ludwigii SAK5, Bacillus cereus SA1, Micrococcus yunnanensis SA2, Enterobacter tabaci SA3, resulted in a significant increase in the growth of Waito‐C rice. The cultural filtrates of bacterial endophytes were tested for phytohormones, including indole‐3‐acetic acid, gibberellins and organic acids. Inoculation of the selected strains considerably reduced the amount of endogenous ABA in rice plants under NaCl stress, however, they increased GSH and sugar content. Similarly, these strains augmented the expression of flavin monooxygenase (OsYUCCA1) and auxin efflux carrier (OsPIN1) genes under salt stress. In conclusion, the pragmatic application of the above selected bacterial strains alleviated the adverse effects of NaCl stress and enhanced rice growth attributes by producing various phytohormones. Endophytic bacteria greatly enhanced growth of rice plants under 150 mm of NaCl stress by mitigating phytohormones, antioxidants, sugar content and gene expression.