Plant growth promoting Curtobacterium albidum strain SRV4: An agriculturally important microbe to alleviate salinity stress in paddy plants

Abstract

• Salt-tolerant Curtobacterium albidum SRV4 strain was isolated from saline soils. • C. albidum SRV4 showed strong plant growth promoting attributes in salinity stress. • Inoculation of C. albidum SRV4 induces salt stress tolerance in paddy plants. • C. albidum SRV4 inoculation significantly enhance paddy yields under soil salinity. Present study examined the inoculation of halo-tolerant plant-growth-promoting-rhizobacteria (PGPR) on paddy plant growth parameters and physiology under different salinity (0, 100, 200 and 300 mM) conditions. Twenty-nine promising halo-tolerant PGPRs were isolated and screened for their PGP traits from the rhizosphere of naturally growing plants of saline soils located at Sandila region of Hardoi, Uttar Pradesh, India. Out of 29 isolates, one most efficient salt-tolerant isolate having potential PGP attributes, was selected for further study. Based on 16S rRNA gene sequencing and BLASTn analysis, the isolate was identified as Curtobacterium albidum SRV4 strain. The SRV4 expressed positive attribute for nitrogen (N 2 ) fixation, exopolysaccharide production (EPS), hydrogen cyanide (HCN), Indole-3-acetic acid (IAA), and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. The higher doses of NaCl negatively affected paddy plant physiology and growth parameters. Paddy plants treated with SRV4 showed significant differences (P < 0.001) in improvement in plant growth parameters, photosynthetic pigment efficiency, membrane stabilization index and proline content. A significant variation (P < 0.001) in enhancement in antioxidative enzymatic activities catalase (CAT), superoxide dismutase (SOD), peroxidase (POX) and ascorbate peroxidase (APX) and K + uptake in paddy plants was noted due to C. albidum SRV4 inoculation. Paddy plant growth parameters (plant root and shoot length, dry weight and tiller number) and antioxidative enzymatic activities were negatively correlated. In conclusion, C. albidum SRV4 has been found as effective microbial agent to improve photosynthetic efficiency, modulation of osmolytes and antioxidative enzymes due to efficient PGP attributes, development of induced systemic tolerance and alleviating salt stress in paddy plants.