Abstract
BackgroundSalinity 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.ResultsWe 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.ConclusionIn 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.
Highlights
Salinity is a major threat to the agriculture industry due to the negative impact of salinity stress on crop productivity
We evaluated the effects of halotolerant isolates ALT29 and ALT43 on soybean growth attributes, ion uptake, reactive oxygen species (ROS) generation and antioxidant production, and salt-related gene expression under NaCl stress at concentrations of 80 mM, 160 mM, and 240 mM
We observed a significant increase in endogenous Abscisic acid (ABA) content in soybean plants under NaCl stress; this effect was mitigated by ALT29 and ALT43 inoculation (Fig. 4a)
Summary
Salinity is a major threat to the agriculture industry due to the negative impact of salinity stress on crop productivity. Soil salinity limits crop productivity by impairing root growth, nutrient uptake, and metabolic processes [1,2,3]. The active rhizosphere zone is reduced as a result of impaired root growth and development, affecting nutrient uptake efficiency. Salinity stress affects physiological, morphological, and biochemical processes, which decrease crop biomass and productivity [2, 3]. Ion toxicity interferes with many physiological processes in plants and leads to chlorosis and necrosis [6, 7]. Salt stress-induced biochemical changes include the modulation of phytohormones (decreases in the stress hormone abscisic acid [ABA] and increases in the defense hormone salicylic acid [SA]), changes in ion uptake (accumulation or removal of ions), antioxidant enzyme activation, reactive oxygen species (ROS) generation and accumulation, and photosynthetic pathway disruption [2]. A decline in photosynthesis will eventually deplete energy reserves, leading to plant starvation, foliar expansion of leaves, and senescence [14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
