Journal Article

Halotolerant bacteria mitigate the effects of salinity stress on soybean growth by regulating secondary metabolites and molecular responses

Kang, Sang-Mo, Jan, Rahmatullah, Khan, Muhammad Aaqil, Imran, Muhammad, Kim, Kyung-Min, Sahile, Atlaw Anbelu, Asaf, Sajjad, Hamayun, Muhammad, Adhikari, Arjun, Lee, In-Jung

2021

Overview

Background Salinity is a major threat to the agriculture industry due to the negative impact of salinity stress on crop productivity. In the present study, we isolated rhizobacteria and evaluated their capacities to promote crop growth under salt stress conditions. Results We isolated rhizospheric bacteria from sand dune flora of Pohang beach, Korea, and screened them for plant growth-promoting (PGP) traits. Among 55 bacterial isolates, 14 produced indole-3-acetic acid (IAA), 10 produced siderophores, and 12 produced extracellular polymeric and phosphate solubilization. Based on these PGP traits, we selected 11 isolates to assess for salinity tolerance. Among them, ALT29 and ALT43 showed the highest tolerance to salinity stress. Next, we tested the culture filtrate of isolates ALT29 and ALT43 for IAA and organic acids to confirm the presence of these PGP products. To investigate the effects of ALT29 and ALT43 on salt tolerance in soybean, we grew seedlings in 0 mM, 80 mM, 160 mM, and 240 mM NaCl treatments, inoculating half with the bacterial isolates. Inoculation with ALT29 and ALT43 significantly increased shoot length (13%), root length (21%), shoot fresh and dry weight (44 and 35%), root fresh and dry weight (9%), chlorophyll content (16–24%), Chl a (8–43%), Chl b (13–46%), and carotenoid (14–39%) content of soybean grown under salt stress. Inoculation with ALT29 and ALT43 also significantly decreased endogenous ABA levels (0.77-fold) and increased endogenous SA contents (6–16%), increased total protein (10–20%) and glutathione contents, and reduced lipid peroxidation (0.8–5-fold), superoxide anion (21–68%), peroxidase (12.14–17.97%), and polyphenol oxidase (11.76–27.06%) contents in soybean under salinity stress. In addition, soybean treated with ALT29 and ALT43 exhibited higher K + uptake (9.34–67.03%) and reduced Na + content (2–4.5-fold). Genes involved in salt tolerance, GmFLD19 and GmNARK , were upregulated under NaCl stress; however, significant decreases in GmFLD19 (3–12-fold) and GmNARK (1.8–3.7-fold) expression were observed in bacterial inoculated plants. Conclusion In conclusion, bacterial isolates ALT29 and ALT43 can mitigate salinity stress and increase plant growth, providing an eco-friendly approach for addressing saline conditions in agricultural production systems.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Abiotic stress / Abscisic acid / Acetic acid / Agricultural industry / Agricultural production / Agricultural research / Agriculture / Antioxidants / Antioxidants - metabolism / Bacteria / Bacteria - isolation & purification / Bacteria - metabolism / Bacterial Physiological Phenomena / Binding sites / Biomedical and Life Sciences / Carotenoids / catechol oxidase / Chlorophyll / Crop growth / Crop production / Crops / culture filtrates / Dry weight / dunes / Environmental aspects / Enzymes / Filtrate / flora / Gene expression / Gene Expression Regulation, Plant / Genetic aspects / Genetic engineering / Glutathione / Glycine max - genetics / Glycine max - growth & development / Glycine max - metabolism / Glycine max - microbiology / Halotolerant PGPR / Hardiness / Host-bacteria relationships / indole acetic acid / Indoleacetic acid / Indoleacetic Acids - metabolism / Inoculation / Korean Peninsula / Life Sciences / Lipid peroxidation / Lipids / Metabolites / Morphology / Organic acids / Peroxidase / Peroxidation / phosphates / Physiological aspects / Physiology / Phytohormones / Plant growth / Plant Growth Regulators - metabolism / Plant metabolites / Plant Sciences / Plant-abiotic interactions / Plants / polymers / Polyphenol oxidase / Potassium - metabolism / protein content / Protein folding / Proteins / Research Article / Rhizosphere / rhizosphere bacteria / Salinity / Salinity effects / Salinity stress / Salinity tolerance / Salt / Salt Stress / Salt tolerance / Salt Tolerance - genetics / Secondary metabolites / Seedlings / Siderophores / Sodium - metabolism / Sodium chloride / Soils, Salts in / Solubilization / Soybean / Soybeans / Stress / superoxide anion / Superoxide anions / Tree Biology / Weight