Potassium-solubilizing Microbes Research Articles

Physiological and rhizospheric response characteristics to cadmium of a newly identified cadmium accumulator Coreopsis grandiflora Hogg. (Asteraceae)

Screening for superior cadmium (Cd) phytoremediation resources and uncovering the mechanisms of plant response to Cd are important for effective phytoremediation of Cd-polluted soils. In this study, the characteristics of Coreopsis grandiflora related to Cd tolerance and accumulation were analyzed to evaluate its Cd phytoremediation potential. The results revealed that C. grandiflora can tolerate up to 20 mg kg−1 of Cd in the soil. This species showed relatively high shoot bioconcentration factors (1.09–1.85) and translocation factors (0.46–0.97) when grown in soils spiked with 5–45 mg kg–1 Cd, suggesting that C. grandiflora is a Cd accumulator and can potentially be used for Cd phytoextraction. Physiological analysis indicated that antioxidant enzymes (i.e., superoxide dismutase, peroxidase, and catalase) and various free amino acids (e.g., proline, histidine, and methionine) participate in Cd detoxification in C. grandiflora grown in soil spiked with 20 mg kg–1 of Cd (Cd20). The overall microbial richness and diversity remained similar between the control (Cd0) and Cd20 soils. However, the abundance of multiple rhizospheric microbial taxa was altered in the Cd20 soil compared with that in the Cd0 soil. Interestingly, many plant growth-promoting microorganisms (e.g., Nocardioides, Flavisolibacter, Rhizobium, Achromobacter, and Penicillium) enriched in the Cd20 soil likely contributed to the growth and vitality of C. grandiflora under Cd stress. Among these, some microorganisms (e.g., Rhizobium, Achromobacter, and Penicillium) likely affected Cd uptake by C. grandiflora. These abundant plant growth-promoting microorganisms potentially interacted with soil pH and the concentrations of Cd and AK in soil. Notably, potassium-solubilizing microbes (e.g., Rhizobium and Penicillium) may effectively solubilize potassium to assist Cd uptake by C. grandiflora. This study provides a new plant resource for Cd phytoextraction and improves our understanding of rhizosphere-associated mechanisms of plant adaptation to Cd-contaminated soil.

Microbial consortium with nitrogen fixing and mineral solubilizing attributes for growth of barley (Hordeum vulgare L.)

Bioinoculants provide better opportunity for ecological farming practices to improve the plant growth and enhanced crop productivity. Different types of bioinoculants containing single microbial culture and multiple microbial strains in single formulation could be used for agricultural sustainability. The different efficient microbial strain in single formulation as a consortium is an emerging trend in the present era. The present study deals with the isolation of nitrogen fixing, phosphorus and potassium solubilizing microbes from rhizospheric soil and root's internal tissues of different cereal/pseudocereal crops and their application as a microbial consortium for the growth of cereal crops. A total of 152 rhizospheric and endophytic bacteria were isolated and screened for the plant growth promoting (PGP) traits of nitrogen fixation, solubilization of phosphorus, and potassium. Among all the isolates, nine were found to fix nitrogen, fifteen and eleven exhibited phosphorus and potassium solubilization activity, respectively. Three selected efficient bacterial strains were identified using 16S rRNA gene sequencing as Erwinia sp. EU-B2SNL1 (N-fixer), Chryseobacterium arthrosphaerae EU-LWNA-37 (P-solubilizer), and Pseudomonas gessardii EU-MRK-19 (K-solubilizer). The inoculation of these three bacterial strains on barley crop as single inoculum and as microbial consortium enhanced the growth and physiological parameters including root/shoot length and biomass, chlorophyll, carotenoids, phenolics, flavonoids and soluble sugar content in comparison with untreated control. The microbial consortium was found to be more effective as compared to single inoculum. The microbial consortium of nitrogen fixing and mineral solubilizing microbes could be used as biofertilizer for plant growth and soil health.

The effectiveness of application of phosphorous and potassium solubilizing multifunctional microbes (Aspergillus costaricaensis and Staphylococcus pasteuri mutants) on maize growth

The use of phosphorus and potassium-solubilizing microbes as biofertilizers is an alternative method to increase the availability of phosphorus and potassium in soils. This study aimed to explore the effectiveness of phosphorus (P) and potassium (K)-solubilizing multifunctional microbes (Aspergillus costaricaensis and Staphylococcus pasteuri mutants) on maize growth. The stages of this study consisted of viability test of P and K solubilizing A. costaricaensis and S. pasteuri mutants in peat and effectiveness test of P and K solubilizing A. costaricaensis and S. pasteuri mutants on maize growth. The results showed that peat carriers could keep the fungi population stable until 18 weeks of storage times. While the bacteria at 6 and 8 weeks storage times showed a slight decrease and stable in the 10 to 12 weeks storage time. The addition of P and K-solubilizing multifunctional microbes could reduce the use of fertilizer up to 50% in the treatment with a combination of easily soluble P or K sources with not-easily soluble P or K sources, as well as a combination of treatments of not-easily soluble P and K sources. This tended to occur in the treatment with the addition of A. costaricaensis mutant.

Potassium solubilization: Strategies to mitigate potassium deficiency in agricultural soils

In soil system, 90%-98% K reserves are non-exchangeable mineral sources and potassium solubilizing microbes (KSMs) can effectively dissolve this mineral. Nowadays focused research on efficient KSMs was started. These microbes are able to enhanced their root colonization and improve plant growth and development. They solubilize K-minerals through different mechanisms including chelation, acidolysis, lowering of pH, exchange reaction, complexation, biofilm formation and secretion of organic acid and polysaccharides. Bio-priming of seed/root through efficient KSMs resulted higher crop productivity, potassium use efficiency (KUE) and mitigate the K-deficiency in soils. In this article we are trying to summarize the KSMs current state of knowledge in agricultural crops. We highlighted the knowledge gaps and suggest future prospective of research, with hope that the use of KSMs in agricultural soil improved soil sustainability.