Effect of Exopolysaccharide-Producing Bacteria and Melatonin on Faba Bean Production in Saline and Non-Saline Soil

Abstract

Soil salinity is a major threat to modern agriculture, as it affects crop growth and development. The present study focuses on the integration of eco-friendly biostimulants in salinity stress as a strategy to achieve the alleviation of abiotic stress. Field experiments were conducted at two locations, consisting of saline and non-saline soil, to investigate the utilization of exopolysaccharide (EPS)-producing bacteria (Azotobacter chroococcum) and melatonin at different concentrations (0, 25, 50, and 100 µM) for alleviating the adverse effects of salinity on the growth and production of faba bean plants. Salinity stress caused a reduction in all measured parameters of the faba bean plants grown in the saline soil relative to the plants grown in the non-saline soil. The addition of bacteria and/or melatonin significantly increased the growth parameters and yield components under both soils compared to the respective control plants. Both bacteria inoculation and melatonin application enhanced N, P, and K concentrations; the proline content; RWC%; and the K+/Na+ ratio; however, Na+ and Cl− concentrations were decreased significantly in salt-stressed faba beans. The combined use of bacteria and melatonin exhibited the highest stimulating effects. The present study recommends the combined use of EPS-producing bacteria and melatonin for the salinity stress management strategy of faba bean.

Roles of Plant Growth-Promoting Rhizobacteria (PGPR) in Stimulating Salinity Stress Defense in Plants: A Review

“…Although PGPR can promote plant growth and improve nutrients uptake, as well as stimulate the synthesis of PhoPs in non-stress environments, their ameliorative roles in plant defense responses are fully expressed till plant crops endure harsh environmental conditions. In the reports of Awad et al [ 123 ] and Abd El-Ghany and Attia [ 124 ], they found that the bacterization of maize ( Zea mays L.) plants and faba bean ( Vicia faba cv. Giza3) seeds with Azotobacter chroococcum , an EPS-producing bacterium, had the decreased Na + and Cl − concentrations and the increased N, P, and K concentrations in their plant tissues.…”

“…Mel exhibits pleiotropic biological activities such as growth regulation [ 148 ] and antioxidative property [ 149 ] and has been widely used as a promising tool for mitigating salt stress in plants. Abd El-Ghany and Attia (2020) [ 124 ] found that the combination of Mel and peat-based inoculants ( Rhizobium leguminosarum , a N fixing bacterium, and Azotobacter chroococcum , an EPS-producing bacterium) synergistically enhanced salt stress tolerance in faba bean plants ( Vicia faba ) as compared to Mel- or inoculants-treated seeds alone. Specifically, in the combined treatment (100 µM Mel + inoculants), the content of Chl a, Chl b, Car, and Pro reached the highest, suggesting the synergistic effects of Mel and beneficial PGPR in improving plant growth and other physiological aspects in salt stress conditions.…”

Mesorhizobium Ciceri as a Biological Tool for Improving Physiological, Biochemical and Antioxidant State of Cicer Aritienum L. by Lowering the Fungicide Induced Oxidative Stress

“…4 panel c). Similarly, M. ciceri BRM5 increased the fresh weight of roots, shoots and whole plant by 29,18 and 22%, respectively (120 DAS) when used with 96 µgKITZkg − 1 compared to un-inoculated plants at the identical dose of KITZ (Table S3, Fig. 4 panel d).…”

Roles of Plant Growth-Promoting Rhizobacteria (PGPR) in Stimulating Salinity Stress Defense in Plants: A Review

“…The productions of ethylene in non-inoculated seedlings and P23 AcdS mutant-inoculated seedlings were comparable, consistent with the study of Cheng et al [18], while ethylene in the WT P23 strain-treated plants was lower, indicating that the WT P23 succeeded in decreasing stress ethylene production. In the reports of Awad et al [105] and Abd El-Ghany and Attia [106], they found that the bacterization of maize (Zea mays L.) plants and faba bean (Vicia faba cv. Giza3) seeds with Azotobacter chroococcum, an EPS-producing bacterium, had the decreased Na + and Clconcentrations and the increased N, P, and K concentrations in their plant tissues.…”