Regulation of soil microbiota and maize growth by siderophore-producing bacteria in Alfisol

Phosphate-solubilizing and siderophore-producing andosol rhizobacteria suppress potato Phytophthora infestans

Beneficial interactions between plants and rhizosphere microorganisms are a major lever for sustainable agriculture in Cameroon. This study evaluated in vitro the potential for promoting plant growth and the antagonistic activity of bacterial strains isolated from the rhizosphere in 12 major districts of western Cameroon where potato ( Solanum tuberosum ) is cultivated. Initially, 169 bacteria were isolated and purified. Eighty-two isolates were screened based on their phosphate solubilization index in solid medium, and 20 isolates were screened for their performance in producing significant amounts of phosphorus in liquid medium. Three isolates were selected based on their overall plant growth-promoting (PGP) performance. These were Corynebacterium sp. (K1, 145 ± 0.2 mg/g of phosphorus solubilized in liquid medium and 12.33 ± 2.30 mm of chitin digestion halo), Bacillus subtilis (K13, 6.49 ± 0.19 mg/ml of IAA biosynthesis and 13.12 ± 0.75 mm of cellulose degradation halo), and Pseudomonas aeruginosa (K5, high production of siderophores with a discoloration ratio of 5.17 ± 2.19 in solid medium, a siderophore production unit of 18.43 ± 0.03 in liquid medium, and a potassium solubilization index of 2.29 ± 0.5). Although all three strains selected at the end of the screening process exhibited in vitro antifungal activity against Phytophthora infestans , K13 achieved total inhibition, as did the synthetic fungicide based on Chlorothalonil 30% and Cymoxanil 6% (100% inhibition). Analysis of the bacterial cultures by gas chromatography coupled with mass spectrophotometry confirmed the presence of compounds with potential plant growth-promoting properties including 1,2-butadiene, para-trifluoromethylbenzoic acid, glycyl-L-proline and 4-hydroxy-6-methyl-3-nitro-2-pyridone. This study highlights the significant biotechnological potential of the isolated strains, particularly Bacillus subtilis K13, as a sustainable alternative to synthetic fungicides. These findings open up promising prospects for the development of indigenous biofertilizers aimed at optimizing potato productivity and disease control in tropical regions.

Plant growth-promoting bacteria from the Cerrado enhance maize development1

ABSTRACT Maize intensive cultivation with excessive fertilizer use generates environmental impacts. Plant growth-promoting bacteria offer a sustainable alternative by favoring nitrogen fixation, phosphorus solubilization, and phytohormone production. This study aimed to evaluate the effect of microorganisms previously recognized as growth promoters in rice on maize biomass and yield. The experiment was conducted under laboratory and greenhouse conditions, in a completely randomized design, with 13 treatments (12 microorganisms and one control). Lysinibacillus boronitolerans (BRM 71995) promoted the greatest increase in shoot dry mass (48.64 %, compared to the control), whereas Acinetobacter sp. (BRM 71990) stood out for root dry mass (217.12 %, compared to the control). For 100-grain weight, Herbaspirillum seropedicae (BRM 71996) increased values by 110.40 %, compared to Bacillus velezensis (BRM 71986). H. seropedicae (BRM 71997) was responsible for the greatest productive gains, increasing the number of grains (57.35 %, compared to the control) and yield per pot (85.14 %, compared to the control).

Sustainable bioformulation of Trichoderma asperellum, Pseudomonas fluorescens, and Bacillus subtilis enhances agricultural productivity in different Brazilian states

ABSTRACT The use of plant growth-promoting microorganisms (PGPM) is a promising strategy to enhance crop productivity while improving soil functionality. This study evaluated the efficacy of fungal-bacterial consortium of Trichoderma asperellum, Pseudomonas fluorescens, and Bacillus subtilis, for promoting the growth of soybean and maize cultivated under distinct edaphoclimatic conditions across Brazil. Field trials were conducted in five locations within Rio Grande do Sul, Santa Catarina, São Paulo, and Minas Gerais. Treatments consisted of a fungal-bacterial consortium (200 g ha-¹, in-furrow at planting) combined with 50% or 100% of the recommended nitrogen rate. Shoot dry biomass, foliar nitrogen (N) and phosphorus (P) concentrations, grain yield, and soil microbial activity determined by fluorescein diacetate hydrolysis were assessed. The fungal-bacterial consortium significantly improved all variables in both crops. In soybean, shoot biomass increased by 10.7-13.4% and grain yield by 9.2-9.9%, while foliar N and P rose by 10.2-12.4%, and soil enzymatic activity increased up to 11.0%. In maize, biomass increased by 10.4-11.8% and grain yield by 13.1-13.9%, with foliar N and P increasing by 9.5-14.1% and soil enzymatic activity by up to 12.5%. Notably, positive responses were maintained under 50% nitrogen fertilization. These findings demonstrate that fungal-bacterial consortium enhances nutrient acquisition and soil microbial activity, improving crop performance under variable environmental conditions and reduced N input, supporting its potential as a biological tool for sustainable nutrient management in soybean and maize systems.

Enhancing Fruit and Vegetable Crops Growth with Exopolysaccharide Produced by Bacillus subtilis

Plant growth-promoting bacteria used in maize cultivation: a systematic literature review (2015–2025)

Maize (Zea mays L.) is one of the most economically important cereals worldwide, contributing significantly to the economies of many countries. Its production model relies heavily on synthetic fertilizers, which contribute to environmental degradation. Plant growth-promoting bacteria (PGPB) are among the sustainable alternatives used to partially replace these inputs, as they can enhance maize growth by optimizing nutrient uptake, increasing disease resistance, and promoting soil health. This study aimed to synthesize information from the last ten years (2015–2025) regarding PGPB applied to maize cultivation. Searches were conducted across five databases—PubMed, ScienceDirect, Scopus, Web of Science, and LILACS—identifying 1,333 articles. After the screening process, 65 articles were included in the review. The included studies were predominantly conducted in two countries: Brazil and China. The most frequently reported bacterial species were Bacillus subtilis (27%), Azospirillum brasilense (23%), and Pseudomonas fluorescens (12%). Among the functional traits, phytohormone production was the most frequent (75%), followed by biological nitrogen fixation (49%), phosphate solubilization (48%), and siderophore production (32%). Biofilm production (8%) was the least frequent trait. Classifying the articles by biostimulation category revealed that the assessment of growth and yield parameters (95%) predominated, whereas abiotic stress tolerance (22%) and biocontrol and crop protection (18%) were less frequent. This review demonstrates that several genera of plant growth-promoting bacteria have been proportionally under-studied in the field over the last decade, highlighting potential knowledge gaps regarding their effects on physiological and yield parameters in maize crops, particularly in the face of stress and global climate challenges.

Rhizosphere Engineering Using a Native Pseudomonas veronii Improves Soil Functioning in Degraded Calcisol

The degradation of Calcisols in the arid regions of Central Asia constrains sustainable agricultural production because of low organic matter content, poor aggregate stability, nutrient limitations, and increasing climatic stress. This study evaluated a rhizosphere engineering approach based on the native plant growth-promoting bacterium Pseudomonas veronii Ps-S/Sh-1503/2022 for the rehabilitation of degraded Calcisols. Four-year field experiments (2022–2025) using Sorghum bicolor assessed plant growth, rhizosphere microbial indicators, physiological responses, pathogen suppression, crop productivity, and implementation feasibility through economic and environmental assessments. Inoculation with P. veronii increased root depth by 45%, improved aboveground biomass, increased the ratio of culturable bacteria to Fusarium spp. from 6.1 to 10.3, and reduced Fusarium abundance by 29.4%. Structural equation modeling suggested that trophic support (42.1%), aggregate stabilization (27.4%), biocontrol (23.3%), and defense-related responses (7.2%) were the principal pathways associated with soil rehabilitation. Economic assessment indicated that the combined inoculation and mineral fertilization treatment provided the highest profitability, while environmental assessment estimated potential reductions in mineral fertilizer use and greenhouse gas emissions. These findings suggest that rhizosphere engineering using a native P. veronii strain represents a promising, economically viable, and climate-smart approach for improving the biological functioning of degraded Calcisols and supporting sustainable agricultural production.