The Halotolerant Rhizobacterium—Pseudomonas koreensis MU2 Enhances Inorganic Silicon and Phosphorus Use Efficiency and Augments Salt Stress Tolerance in Soybean (Glycine max L.)

Abstract

Optimizing nutrient usage in plants is vital for a sustainable yield under biotic and abiotic stresses. Since silicon and phosphorus are considered key elements for plant growth, this study assessed the efficient supplementation strategy of silicon and phosphorus in soybean plants under salt stress through inoculation using the rhizospheric strain—Pseudomonas koreensis MU2. The screening analysis of MU2 showed its high salt-tolerant potential, which solubilizes both silicate and phosphate. The isolate, MU2 produced gibberellic acid (GA1, GA3) and organic acids (malic acid, citric acid, acetic acid, and tartaric acid) in pure culture under both normal and salt-stressed conditions. The combined application of MU2, silicon, and phosphorus significantly improved silicon and phosphorus uptake, reduced Na+ ion influx by 70%, and enhanced K+ uptake by 46% in the shoots of soybean plants grown under salt-stress conditions. MU2 inoculation upregulated the salt-resistant genes GmST1, GmSALT3, and GmAKT2, which significantly reduced the endogenous hormones abscisic acid and jasmonic acid while, it enhanced the salicylic acid content of soybean. In addition, MU2 inoculation strengthened the host’s antioxidant system through the reduction of lipid peroxidation and proline while, it enhanced the reduced glutathione content. Moreover, MU2 inoculation promoted root and shoot length, plant biomass, and the chlorophyll content of soybean plants. These findings suggest that MU2 could be a potential biofertilizer catalyst for the amplification of the use efficiency of silicon and phosphorus fertilizers to mitigate salt stress.

Phytobeneficial and salt stress mitigating efficacy of IAA producing salt tolerant strains in Gossypium hirsutum

“…ST bacterial strains helped to maintain the proline content under stressed condition to the level of unstressed condition. To strengthen our finding that ST PGPR helped to lower the proline content similar results were also reported by number of studies ( Adhikari et al, 2020 , Sapre et al, 2018 ) in which the halotolerant PGPR inoculation lower the proline content in oat and soybean, respectively. In our study out of ten finally selected ST PGPR nine were Bacillus strains, our study coincided with previous findings where Bacillus species considered as predominant PGP bacteria ( Akinrinlola et al, 2018 , Radhakrishnan et al, 2017 ) and ST5, ST16 and ST20 isolated from rhizosphere of Solanum lycopersicum , Triticum aestivum and Allium sativum , respectively showed the most promising results.…”

Bioinoculants as Promising Complement of Chemical Fertilizers for a More Sustainable Agricultural Practice

“…Besides, the inoculation possibly improved the translocation of S and K, whose amounts resulted higher in leaves than in roots, when compared to the control. Indeed, related P. koreensis strains was recently shown to feature relevant K solubilizing ability in soil, thus increasing the K bioavailability to plants (Reyes-Castillo et al, 2019;Adhikari et al, 2020). Very interestingly, the Fe content was significantly increased, and this effect might be correlated to the capacity of the same strain to produce siderophores, organic compounds which increase the Fe bioavailability (Scagliola et al, 2016).…”

Drought and Plant Community Composition Affect the Metabolic and Genotypic Diversity of Pseudomonas Strains in Grassland Soils

“…P. koreensis has been characterized from agricultural soil [ 41 ]. Many strains of this species express plant growth-promoting activities, such as P and K solubilization, as well as siderophore and IAA production [ 4 , 42 ]. P. putida is a widely studied species with a highly versatile metabolism, that solubilizes K and P [ 43 , 44 ], and produces siderophores [ 45 ].…”