Responses of growth and quality of Glycyrrhiza uralensis to salt-alkali-tolerant microbial inoculant via the remodeling of rhizosphere microenvironments in moderate and severe saline-alkali soils
The combined application of microbial inoculation and seedling transplanting is recommended for large-scale and high-quality cultivation of G. uralensis in moderately saline-alkali soils of arid northwestern China, as this integrated practice maximizes plant growth, medicinal compound accumulation, and rhizosphere microenvironment optimization.
Abstract
Glycyrrhiza uralensis
is an ecologically and economically important medicinal species for saline-alkali land restoration in arid northwest China. Nevertheless, excessive soil salinity, alkalinity and nutrient deficiency substantially restrict its growth and degrade medicinal quality. Microbial inoculation serves as a promising strategy to alleviate salt-alkali stress, yet the field stability and rhizosphere regulatory mechanisms of inoculants under diverse cultivation regimes remain poorly understood, limiting their field application. Building on our prior strain screening and preliminary field validation, this study utilized a composite inoculant containing
Pseudomonas silesiensis
,
Arthrobacter
sp. GCG3 and
Rhizobium
sp. DG1, and investigated its effects on
G. uralensis
growth, bioactive metabolites, rhizosphere soil properties and microbial communities under three field viable cultivation scenarios (direct seeding and seedling transplanting in moderately saline-alkali soil, seedling transplanting in severely saline-alkali soil) with respective tailored fertilization, planting densities and inoculation schedules. The results revealed that under all scenarios, the inoculation induced an increasing trend in the root dry weight and bioactive compound accumulation, with markedly higher dry root weight in seedling transplanting scenarios (101.68%, moderately saline-alkali soil; 53.96%, severely saline-alkali soil,
P
< 0.05). Glycyrrhizic acid contents per plant rose by 57.32, 106.11 and 6.56%, while those of liquiritin rose by 42.50, 177.24 and 42.34%, respectively. The inoculant barely altered rhizosphere pH and soluble salt contents, yet universally regulated rhizosphere nutrient pools, which were reflected in a uniform reduction of nitrate nitrogen and scenario-specific shifts in other available nutrients as well as soil organic matter. High-throughput sequencing verified that this inoculant could reshape the rhizosphere microbial community structure of
G. uralensis
; across all scenarios, the relative abundance of pathogenic
Fusarium
significantly decreased, and indigenous beneficial bacteria and fungi were enriched. This inoculant exhibited stable growth-promoting effects across all cultivation regimes. The combined application of microbial inoculation and seedling transplanting is therefore recommended for large-scale and high-quality cultivation of
G. uralensis
in moderately saline-alkali soils of arid northwestern China, as this integrated practice maximizes plant growth, medicinal compound accumulation, and rhizosphere microenvironment optimization.
It is suggested that selected halotolerant isolates possess multifunctional traits including salt tolerance and potential nutrient-solubilizing capacity, making them promising candidates for biofertilizer development and sustainable agriculture in salt-affected regions.
H. Dixit, Ranjan Singh, Sanjay Arora et al.· Journal of Soil and Water Co...· 0 citations
Enhanced soil salinity is a major constraint to rice production in the coastal regions of Bangladesh. Salinity stress impairs nutrient uptake and induces ionic toxicity and osmotic stress, while excessive use of chemical fertilizers degrades soil health and causes environmental pollution. A novel salt-tolerant endophytic fungus, Aspergillus welwitschiae Ocstreb1, isolated from the halophytic wild rice Oryza coarctata, exhibited multiple plant growth–promoting traits under both non-saline and 900 mM salt-stress conditions in vitro. These findings suggest that Ocstreb1-based biofertilizer could serve as an eco-friendly and cost-effective alternative to enhance rice productivity under saline conditions. In this experiment, the biofertilizer was prepared using fungal spores produced on wheat bran and subsequently mixed with talcum powder as a carrier. Field trials were conducted following a randomized complete block design (RCBD), incorporating different levels of chemical fertilizer application (0%, 80%, and 100% of the BRRI-recommended NPKSZn rates) in both biofertilizer-treated and untreated plants. Compared with the 100% chemical fertilizer treatment, the combined application of biofertilizer and 80% chemical fertilizer resulted in a comparable yield in Barguna and increased yield of 196.6 kg ha⁻¹ in Satkhira. Profitability analysis showed that this treatment provided an additional economic benefit of USD 48–68 ha⁻¹ over the 100% chemical fertilizer treatment. Moreover, fumonisin B1 levels in grains from biofertilizer-treated plants were negligible. In conclusion, commercial production of this biofertilizer will pave the way for enhancing rice yield with less use of chemical fertilizer while promoting sustainable agricultural practice particularly in areas affected by salinity stress.
Amit Chowdhury, J. Bhattacharya, Md. Iyasir Arafat et al.· Discover Agriculture· 0 citations
This study evaluated the potential of the salt-alkali-tolerant actinobacterium Streptomyces luteus TRM 45540, isolated from Lop Nur saline-alkali soil in Xinjiang, to alleviate pH-related iron deficiency and promote pepper growth. We hypothesized that this strain could mobilize and compete for soil iron via siderophore production, thereby benefiting plants under variable-pH conditions. To test this hypothesis, we compared its effects with conventional iron fertilizers (EDDHA-Fe₆, ferrous sulfate) and compound microbial fertilizer on pepper growth, soil physicochemical properties, and rhizosphere microbial communities in acidic (pH 5) and alkaline (pH 7.69) soils. TRM 45540 exhibited good stress tolerance, growing well at 3%-9% NaCl and pH 9-12. In both soil types, it significantly promoted pepper growth: fresh weight was increased by over 44% in acidic soil relative to the control, while root and stem lengths were elevated by 26%-91% in alkaline soil compared with conventional amendment groups. The strain increased the content of indigenous soluble iron in soil, raising soluble iron to 42 mg/kg- 1 in acidic soil without exogenous iron addition, neutralized acidic soil toward neutral pH, increased total nitrogen to 6.5 g/kg- 1, and enhanced phosphorus and potassium availability. Redundancy analysis identified pH and total iron as the dominant factors shaping microbial communities in acidic and alkaline soils, respectively. KEGG pathway enrichment revealed significant changes in organic pollutant degradation, nutrient metabolism, and stress response pathways following TRM 45540 inoculation. The strain enriched functional microorganisms related to siderophore secretion and nitrogen fixation, thereby improving soil microbial diversity and richness, while compound microbial fertilizer was associated with relatively lower microbial community activity. These findings demonstrate that S. luteus TRM 45540, with cross-pH adaptability and functional stability, enhances pepper growth and soil quality via synergistic effects of stress tolerance, nutrient activation (especially iron mobilization), and microbial community regulation. This strain provides a promising microbial inoculant for sustainable pepper production in variable-pH soils, especially saline-alkali soils.
Yi-huang Chen, Xirui Wang, Yuxin Si et al.· BMC Plant Biology· 0 citations
Findings indicate that Cupriavidus metallidurans YX16 is a salt-tolerant plant growth-promoting rhizobacterium (PGPR) that effectively alleviates salt-induced damage and promotes maize growth, providing a basis for the development of microbial agents for the amelioration of saline-alkali soils.
Increasing soil salinization severely threatens agricultural productivity in many coastal ecosystems and dryland regions. In this study, two halotolerant endophytic bacterial strains, Bacillus sp. CR-4 and Streptomyces sp. CR-7, was isolated from Catharanthus roseus collected from saline coastal areas and evaluated for its plant growth-promoting traits and salt stress-mitigation ability. The selected isolates displayed diverse plant-beneficial properties such as phytohormone synthesis, nutrient mobilization capacity, and stress-associated enzymatic activities. Inoculation with these strains significantly enhanced plant height, biomass, relative water content, and chlorophyll index under 100 mM NaCl stress in greenhouse conditions. Field trials in saline soils further confirmed improved survival, flower yield, and physiological traits in treated plants. Biochemical analyses revealed increased proline accumulation, enhanced antioxidant enzyme activities (SOD, POD, CAT), and reduced membrane damage, highlighting the stress mitigation effects of these endophytes. Multivariate analysis confirmed strong correlations between microbial traits and plant physiological performance. These results demonstrate the potential of CR-4 and CR-7 as effective bioinoculants for the sustainable cultivation of C. roseus and possibly other crops in salt-affected areas.
Soil salinization severely threatens agricultural productivity and ecosystem sustainability, particularly in coastal regions. Halophyte-based phytoremediation is a promising strategy, yet how rhizosphere soil legacy effects at different restoration ages influence subsequent plant growth and microbial communities remains poorly understood. Here, rhizosphere soils of Nitraria tangutorum at 1- (BC-1), 2- (BC-2), and 3-year (BC-3) restoration stages and non-rhizosphere bulk soil (CK) were sampled, with alfalfa cultivated as a bioindicator to assess soil physicochemical properties, plant growth, stress physiology, and rhizosphere microbiota. With increasing restoration age, rhizosphere soil shifted from a state of salt accumulation and nutrient deficiency to one of salt depletion and nutrient enrichment, with BC-3 exhibiting the highest soil organic matter, total phosphorus, and alkali-hydrolyzable nitrogen and the lowest total salt and soluble Na+. Alfalfa growth was suppressed in BC-1 and BC-2 soils, but significantly promoted in BC-3, accompanied by the lowest malondialdehyde and proline content, indicating effective alleviation of oxidative and osmotic stress. Microbial diversity peaked at BC-2, whereas the total proportion of halotolerant bacteria declined from 0.44 (BC-1) to 0.34 in BC-3 (significantly lower than CK), suggesting a successional shift from a stress-dominated community toward a functionally specialized consortium. Regression analyses identified soluble sodium as the variable most strongly associated with growth inhibition (R2 > 0.80) for plant height and root length. We suggest soluble sodium may represent the principal factor associated with growth inhibition and that a positive-feedback loop among plant Na+ sequestration, microbial carbon sequestration, and soil maturation may sustain long-term saline–alkali soil improvement. These findings suggest a three-stage successional mechanism and highlight the critical role of restoration age in mediating plant–microbe–soil synergistic remediation of coastal saline soils.