Salt-tolerant bacteria enhance the growth of mung bean (Vigna radiata L.) and uptake of nutrients, and mobilize sodium ions under salt stress condition

Abstract

Salinity is one of the significant abiotic stresses that exert harmful effects on plant growth and crop production. It has been reported that the harmfulness of salinity can be mitigated by the use of salt-tolerant plant growth-promoting (PGP) bacteria. In this study, four bacteria were selected from a total of 30 cultures, based on salt-tolerant and PGP properties. The isolates were found to produce indole acetic acid (8.49–19.42 μg/ml), siderophore (36.04–61.77%), and solubilize potassium and inorganic phosphate. Identification based on 16S rRNA gene sequencing revealed that the isolates belonged to Cronobacter (two isolates) and Enterobacter (two isolates). Inoculation of PGP bacteria under 2 and 10% salinity stress showed enhanced plant growth parameters in Vigna radiata compared to both salinity and non-salinity control plants. The rate of germination (113.32–206.64%), root length (128.79–525.31%), shoot length (34.09–50.32%), fresh weight, and dry weight were 3-fold higher in bacteria-treated seeds than control plants. The estimation of chlorophyll (1–5-fold), carotenoids (1–4-fold), and proline content (3.65–14.45%) was also higher compared to control plants. Further, the bacterized seeds showed enhanced nitrogen and phosphorous uptake and mobilized sodium ions from roots to leaves. Overall the strains SS4 and SS5 performed well in both 2 and 10% salt-amended soils. These strains could be formulated as a bioinoculant to mitigate the salinity stress in salinized soils.

NOVELTY STATEMENT

Salinity severely affects the growth and productivity of Vigna radiate (mung bean) worldwide. Approximately 50 mM concentration of NaCl can cause >60% yield loss of mung bean. In this study, inoculation of salt-tolerant root nodule-associated plant growth-promoting bacteria showed 2–3-fold enhancements in mung bean plant growth, biomass, and physiology even at 2 and 10% salinity stress. Further, the inoculated mung bean plants showed an increment in the uptake of nitrogen and phosphorous in the salinized conditions and mobilized the Na⁺ ions from root to shoot to reduce the toxicity posed by Na⁺ ions. Therefore the strains identified in this study could be formulated to mitigate the salinity stress and improve the mung bean growth in salinized soils.

Keywords:

• Cronobacter
• Enterobacter
• photosynthetic pigments
• salinity
• Vigna radiata

Ethical approval

All authors read the manuscript and gave their consent for publication.

Acknowledgments

The authors thank the management of Uka Tarsadia University for their support, Eurofins Pvt Ltd. to identify bacteria by sequencing, and Environment Care Laboratory to estimate sodium, nitrogen, and phosphorus contents.

Disclosure statement

Shreya Desai, Jemisha Mistry, Firdosh Shah, Sapna Chandwani, Natarajan Amaresan, and Naga Rathna Supriya declare that they have no conflict of interest.

Author contributions

NRS and NA designed the work. SD, JS, FS, and SC performed the experiments and statistical analysis of data. DS, NRS, and NA drafted and proofread final the article.