Search Results (95)

Background/Objective: Sewage sludge (biosolids) is increasingly reused as a fertilizer to recycle nutrients and close material cycles; however, concerns persist regarding antibiotics and antimicrobial resistance. This study evaluated the agronomic safety and microbiological integrity of biosolid fertilization in soybean and maize systems, with particular attention to grain quality and food safety. Methods: Soybean and maize were cultivated in greenhouse microcosms under biosolid or mineral fertilization. Soil, roots, shoots, and grains were analyzed for antibiotic residues using LC–MS/MS and antibiotic-resistant bacteria (ARB) using culture-based assays. Minimum inhibitory concentrations for isolates from grains were compared with clinical breakpoints to verify phenotypic susceptibility. Multivariate analyses (PCA) integrating real-time antibiotic concentrations and updated resistance indicators were performed using centered and scaled data. Results: Fluoroquinolones were the predominant residues introduced by biosolids and exhibited consistent time-dependent declines across all treatments, although low concentrations remained detectable at 90 d in several soil–fertilizer–crop combinations. Tetracyclines, macrolides, and sulfonamides showed similar decreasing trends, with planted soils displaying faster dissipation than bulk control soils. Biosolid fertilization increased shoot biomass by 1.5–2.3-fold and nitrogen, phosphorus, and potassium uptake by 30–60% without impairing soybean nodulation or nitrogenase function. ARB was observed in all soils, including mineral and plant-free controls, indicating a natural background resistome. Ciprofloxacin-resistant isolates were detected in one simple sampling point, and MDR proportions were transient (67%), returning to their background levels by 45–90 days. PCA showed that crop presence, not fertilizer type, was the primary driver of microbial ordination, and that antibiotic concentrations and resistance indicators were only weakly aligned, indicating a limited selective pressure. No antibiotic residues or phenotypically resistant bacteria were detected in the soybean or maize grains. Conclusions: Updated residue, resistance, and multivariate data confirmed that biosolids did not induce, amplify, or transfer antibiotic resistance and maintained complete grain safety. Properly treated biosolids function as safe, agronomically beneficial fertilizers aligned with One Health goals, enhancing crop productivity without compromising food quality or increasing antimicrobial resistance. Full article

Cold stress during early growth can severely impact nodulation, growth, and yield in legumes. This study evaluated cold plasma (CP) seed treatment as a strategy to enhance growth and symbiotic nitrogen fixation (SNF) in field pea (Pisum sativum L.) and soybean (Glycine max L.) under cold stress during early growth. CP-treated and non-treated seeds were grown at 8 °C (cold) or 15 °C (control) for 5 weeks, after which half of the plants were harvested for nodulation and growth assessments. The remainder were transferred to greenhouse conditions until maturity. The cold stress suppressed nodulation and reduced biomass in both legumes. Soybean recovered under greenhouse conditions; however, pea yield remained suppressed. At maturity, SNF traits in both legumes were not significantly affected by early cold stress. CP seed treatment showed little effect under severe cold (8 °C) but at 15 °C, improved root growth in pea and enhanced root and shoot biomass and pod and seed yield in soybean. These findings suggest that CP seed treatment can improve legume performance under moderate cold. However, the current CP seed treatment conditions did not improve the stress resistance of both crops under severe cold stress. Full article

Arsenic (As) contamination poses a major challenge to sustainable crop production, particularly in legumes such as peanut (Arachis hypogaea L.), where it disrupts growth, nodulation, and redox homeostasis. This study evaluated the potential of circular-economy-based amendments derived from spent mushroom substrate (SMS) of Pleurotus djamor and plant growth-promoting bacteria (PGPB) to mitigate As stress in peanut plants. Six growth conditions were tested under 20 µM arsenate, including single and combined inoculations with P. djamor and Pseudomonas fluorescens, as well as a residue-only benchmark (E). Results showed that the unamended control (AP) exhibited the highest As accumulation, oxidative stress (H₂O₂, TBARs), and biomass loss, whereas SMS-based amendments attenuated these effects. Treatments HB (SMS + P. djamor + PGPB) and B (SMS + PGPB) combined low As translocation with enhanced antioxidant performance (SOD, CAT), maintaining growth and pigment stability. Amendment H (SMS + P. djamor) preferentially activated phytochelatin-related genes (PCS2, CAD1), while E minimized As uptake but lacked circular applicability. Overall, SMS-PGPB interactions promoted As retention in roots and strengthened ROS-scavenging defenses. These findings highlight SMS-based amendments as viable, sustainable strategies to enhance peanut quality and resilience under As stress, supporting their integration into circular agronomic systems. Full article

Cobalt, molybdenum, and nickel are elements directly involved in biological nitrogen fixation in legume plants. However, there is a lack of information about the effects of the interaction among these elements on seed vigor and plant development. This study aimed to evaluate the effects of different doses of these elements on soybean seeds with higher and lower vigor, focusing on nitrogen metabolism and plant development under controlled conditions. The two lots of soybean seeds (higher and lower vigor) were treated with doses of 0, 2, 4, 6, and 8 mL kg⁻¹ of seeds of a liquid commercial product composed of cobalt, molybdenum, and nickel. At the full flowering stage, urease and nitrogenase activities, dry biomass of shoots, roots, and nodules, nitrogen concentration in shoots, plant height, number of nodules, and the efficiency of biological nitrogen fixation (measured by nitrogen-15 isotopic ratio) were assessed. Urease activity increased by 191% in high-vigor seed plants and 65% in low-vigor seed plants. Nitrogenase activity was higher in higher-vigor plants. Nodule dry biomass increased by 42% in lower-vigor plants compared to the control treatment, while in higher-vigor plants, it decreased with increasing doses. Shoot biomass was 30% higher than the control at the 2 mL kg⁻¹ dose. In general, the best responses to the application of the elements in the evaluated variables were observed with the doses of 2 and 4 mL kg⁻¹. It is concluded that the appropriate application of cobalt, molybdenum, and nickel on seeds enhances growth and symbiotic efficiency. However, excessive doses may cause phytotoxic effects. Full article

Background: The increase in potentially toxic elements (PTEs) in the soil is worrying, especially in agricultural soils due to the bioaccumulation factor. Copper (Cu) and iron (Fe) are micronutrients, responsible for important functions in the plant body, but the high availability of these elements in the soil can cause soil contamination and toxicity in plants; consequently, they can be considered PTEs. Objectives: The focus of this study is to understand the physiological responses (pigments, gas exchange, growth, biomass, accumulation) of Canavalia ensiformis to high levels of Cu and Fe in the soil, in isolation, and to identify which PTE is most harmful to its development. Methods: Two experiments (Cu and Fe) were conducted simultaneously in a greenhouse. Treatments of 50, 150, 250, and 350 mg dm⁻³ of soil for each element (CuSO₄*5H₂O and FeSO₄*7H₂O) were incorporated into the soil (Oxisol) of each experimental unit (4 dm³ pot), in addition to the control. C. ensiformis seeds were sown directly in soil enriched with Cu and Fe, respectively, and after emergence they were cultivated for 90 days. Results: Changes in chlorophyll levels caused direct effects on gas exchange, shoot biomass, root development, nodulation, and total plant biomass. The tolerance of the species is dependent on chlorophyll levels and gas exchange. There was accumulation of both PTEs in the roots and low translocation to the shoot. Conclusions: The plants were tolerant to Fe treatments; however, they were not tolerant to Cu treatments (T150–T350). Excess Cu was more detrimental to plant development. Full article

The diversification of cover crops grown in soils with granulometric variability may potentially enhance microbial community and enzyme activities. Thus, the main goal was to evaluate the effect of autumn/winter cover crop sequences and cash crops in spring/summer on soil microbial biomass and enzyme activities. The experiment was conducted in open-field microplots (10 m × 1 m × 0.7 m), containing soils from B horizon of five Oxisols with granulometric variability and clay content ranging from 17 to 80 dag kg⁻¹. The treatments were three cover crops and a winter fallow with a completely randomized experimental design with three replicates. Soil samples from the 0–10 cm layer were collected to analyze soil microbial biomass of carbon and nitrogen, enzyme activities of the acid phosphatase, arylsulfatase, urease, and fluorescein diacetate hydrolysis. The number of nodules in soybean roots was average 63 ± 14.42 nodules per plant and dry mass of nodules was 169 ± 13.74 mg plant⁻¹. Soybean nodulation and N uptake ensured the supply of nitrogen to the soybean plants with 331 ± 82 mg plant⁻¹. Overall, diversified autumn/winter cover crop sequences provide plant residue, containing nutrients, and different carbon/nitrogen, which alters microbial biomass, the ratio of C_mic/N_mic, basal respiration, and soil enzyme activities within each Oxisol with different particle size distribution. Full article

Small signaling peptides play crucial roles in the regulation of legume–rhizobia symbiosis, yet their potential as exogenous biostimulants remains largely unexplored. In this study, we evaluated the effects of foliar application of the synthetic peptides ENOD40 and CEP1 on common bean (Phaseolus vulgaris) under both greenhouse and field conditions. Using a factorial design, we examined gene expression patterns, nodulation parameters, and yield-related traits in response to peptide treatments alone or in combination with Rhizobium. Results showed that ENOD40 and CEP1 significantly enhanced the transcription of key symbiotic signaling genes (PvENOD40, PvSYMRK, PvCCaMK, PvCYCLOPS, PvVAPYRIN) and modulated defense-related genes (PvAOS, PvICS), with the strongest effects observed at concentrations of 10⁻⁷ M and 10⁻⁸ M. In greenhouse assays, peptide-treated plants exhibited increased root and shoot biomass, nodule number, and seed yield. Field trials confirmed these responses, with CEP1 10⁻⁷ M + Rhizobium treatment achieving the highest grain yield (3322 kg ha⁻¹). Our findings provide the first evidence that ENOD40 and CEP1 peptides can function as foliar-applied biostimulants to enhance nodulation efficiency and improve yield in legumes. This approach offers a promising and sustainable strategy to reduce chemical nitrogen inputs and support biological nitrogen fixation in agricultural systems. Full article

Salinity is a major abiotic stress limiting black gram (Vigna mungo) productivity, particularly in arid and semi-arid regions. Saline soils negatively impact plant growth, nodulation, nitrogen fixation, and yield. This study evaluated the efficacy of co-inoculating salt-tolerant plant growth-promoting bacteria Paenibacillus sp. SPR11 and Bradyrhizobium yuanmingense PR3 on black gram performance under saline field conditions (EC: 8.87 dS m⁻¹; pH: 8.37) with low organic carbon (0.6%) and nutrient deficiencies. In vitro assays demonstrated the biocontrol potential of SPR11, inhibiting Fusarium oxysporum and Macrophomina phaseolina by 76% and 62%, respectively. Germination assays and net house experiments under 300 mM NaCl stress showed that co-inoculation significantly improved physiological traits, including germination rate, root length (61.39%), shoot biomass (59.95%), and nitrogen fixation (52.4%) in nitrogen-free media. Field trials further revealed enhanced stress tolerance markers: chlorophyll content increased by 54.74%, proline by 50.89%, and antioxidant enzyme activities (SOD, CAT, PAL) were significantly upregulated. Electrolyte leakage was reduced by 55.77%, indicating improved membrane stability. Agronomic performance also improved, with co-inoculated plants showing increased root length (7.19%), grain yield (15.55 q ha⁻¹; 77.04% over control), total biomass (26.73 q ha⁻¹; 57.06%), and straw yield (8.18 q ha⁻¹). Pod number, seed count, and seed weight were also enhanced. Nutrient analysis showed elevated uptake of nitrogen, phosphorus, potassium, and key micronutrients (Zn, Fe) in both grain and straw. To the best of our knowledge, this is the very first field-based report demonstrating the synergistic benefits of co-inoculating Paenibacillus sp. SPR11 and Bradyrhizobium yuanmingense PR3 in black gram under saline, nutrient-poor conditions without external nitrogen inputs. The results highlight a sustainable strategy to enhance legume productivity and resilience in salt-affected soils. Full article

The chickpea (Cicer arietinum L.) is a key legume crop in Mediterranean agriculture, valued for its nutritional profile and adaptability. However, its productivity is severely impacted by drought stress. To identify microbial solutions that enhance drought resilience, we isolated seven Mesorhizobium strains from chickpea nodules collected in southern Spain and evaluated their cultivar-specific symbiotic performance. Two commercial cultivars (Pedrosillano and Blanco Lechoso) and twenty chickpea germplasms were tested under growth chamber and greenhouse conditions, both with and without drought stress. Initial screening in a sterile substrate using nodulation assays, shoot/root dry weight measurements, and acetylene reduction assays identified three elite strains (ISC11, ISC15, and ISC25) with superior symbiotic performance and nitrogenase activity. Greenhouse trials under reduced irrigation demonstrated that several strain–cultivar combinations significantly mitigated drought effects on plant biomass, with specific interactions (e.g., ISC25 with RR-98 or BT6-19) preserving over 70% of shoot biomass relative to controls. Whole-genome sequencing of the elite strains revealed diverse taxonomic affiliations—ISC11 as Mesorhizobium ciceri, ISC15 as Mesorhizobium mediterraneum, and ISC25 likely representing a novel species. Genome mining identified plant growth-promoting traits including ACC deaminase genes (in ISC11 and ISC25) and genes coding for auxin biosynthesis-related enzymes. Our findings highlight the potential of targeted rhizobial inoculants tailored to chickpea cultivars to improve crop performance under water-limiting conditions. Full article

Although many plant families are predominantly mycorrhizal, few symbiotic relationships between plants and arbuscular mycorrhizal fungi (AMF) have been thoroughly studied. Mycorrhized plants tend to exhibit greater tolerance to soil-borne pathogens and enhanced plant defence. Legumes, including common bean (Phaseolus vulgaris L.), are essential sources of protein globally. To improve common bean productivity, identifying efficient native microsymbionts is crucial. This study aimed to identify native AMF associated with common bean roots that could act as biostimulants and protect against soil diseases under varying environmental conditions. Agronomic trials were conducted at MBG-CSIC (Pontevedra, Spain) in 2021 and 2022, testing combinations of nitrogen fertilization, Burkholderia alba, Trichoderma harzianum, and a control. Traits such as nodulation, biomass, plant vigor, disease severity, nutrient content, and yield were evaluated. Four AMF species across three genera were identified. No consistent pattern was observed in AMF influence on agronomic traits. However, reduced mycorrhization in 2022 was associated with decreased nodulation, likely due to higher temperatures. Surprisingly, yields were higher in 2022 despite lower colonization. These findings suggest that intelligent use of AMF could reduce pesticide use, enhance sustainability, and promote healthier food systems. Continued research and conservation efforts are essential to optimize their benefits in legume production. Full article

Copper (Cu) is a naturally occurring element in soils, and at adequate concentrations, it is essential for plant survival. However, excessive Cu can lead to contamination, impairing soil quality and affecting the development of living organisms. The present study aimed to evaluate the physiological responses of Stizolobium aterrimum plants grown in soils contaminated with increasing doses of copper. The experiment was conducted in a greenhouse under controlled temperature conditions. Five treatments were applied (0, 30, 60, 240, and 480 mg dm⁻³). After 51 days of cultivation, the plants were harvested, and their tissues were separated into leaves, roots, and nodules. Nitrogen compounds were extracted, and the contents of total soluble amino acids, ureides, and soluble proteins were quantified. The activity of the nitrogenase enzyme was analyzed in vivo. The results indicate that Stizolobium aterrimum is partially tolerant to copper contamination, exhibiting adequate growth and metabolism in the presence of moderate Cu concentrations. However, increasing Cu levels in the soil reduce fresh biomass production and lead to higher copper accumulation in the root system. High soil Cu concentrations also affect the absorption of other nutrients, in addition to copper itself. Cu doses around 240 mg dm³ can already be considered toxic. Full article

The interactive effects between nano-silicon dioxide (n-SiO₂) and elevated CO₂ (eCO₂; 645 ppm) on soybean physiology, nitrogen fixation, and nutrient dynamics under climate stress remain underexplored. This study elucidates their combined effects under ambient (aCO₂; 410 ppm) and eCO₂ conditions. eCO₂ + n-SiO₂ synergistically enhanced shoot length (30%), total chlorophyll (112.15%), and photosynthetic rate (103.23%), alongside improved stomatal conductance and intercellular CO₂ (17.19%), optimizing carbon assimilation. Nodulation efficiency increased, with nodule number and biomass rising by 48.3% and 53.6%, respectively, under eCO₂ + n-SiO₂ versus aCO₂. N-assimilation enzymes (nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase) surged by 38.5–52.1%, enhancing nitrogen metabolism. Concurrently, phytohormones (16–21%) and antioxidant activities (15–22%) increased, reducing oxidative markers (18–22%), and bolstering stress resilience. Nutrient homeostasis improved, with P, K, Mg, Cu, Fe, Zn, and Mn elevating in roots (13–41%) and shoots (13–17%), except shoot Fe and Zn. These findings demonstrate that n-SiO₂ potentiates eCO₂-driven benefits, amplifying photosynthetic efficiency, nitrogen fixation, and stress adaptation through enhanced biochemical and nutrient regulation. This synergy underscores n-SiO₂ role in optimizing crop performance under future CO₂-rich climates, advocating nano-fertilizers as sustainable tools for climate-resilient agriculture. Full article

Soybeans have been cultivated in Poland for more than 140 years. However, Poland’s cold and water-deficient climatic conditions hinder soybean cultivation. Although the availability of suitable soybean varieties in Poland contributes to meeting the demand for soybean production, it is important to identify rhizobial inoculants in Polish soils suitable for soybean cultivation. In this study, we cultivated soybean varieties (Abelina, Merlin, and Sultana) grown in soils taken from four regions in Poland and isolated 330 strains from soybean root nodules. 16S rRNA gene sequencing identified 49 strains of highly stress-tolerant nodule-associated bacteria, including Bradyrhizobium, Rhizobium, Ensifer, Tardiphaga, and Ralstonia spp. Several isolates exhibited positive effects on soybean growth under cold and water-deficient conditions. In particular, the isolate Bradyrhizobium japonicum PSN49, which is phylogenetically similar to B. japonicum USDA 123, increased plant biomass and nodule formation in the soybean cultivar Abelina under abiotic stress conditions due to its high nitrogen-fixing activity. Whole-genome comparisons between PSN49 and other Bradyrhizobium strains revealed that trehalose biosynthesis genes and cold shock proteins contributed to cold stress tolerance. These findings and the strains identified in this study will enhance soybean production and deepen the understanding of the soybean–rhizobium relationship in Poland. Full article

Although tea (Camellia sinensis)/soybean (Glycine max) intercropping is widely applied in tea gardens, the underlying mechanisms driving tea quality promotion remain largely unclear. This study explores the effects of intercropping on tea quality, soil nutrient availability, and soybean growth and analyzes their mutual relationship. Field experiments revealed that intercropping increased tea leaf water extracts, polyphenols, and amino acids by 4.36–8.99%, 14.76–15.23%, and 14.73–16.36%, respectively, across two growth stages. Furthermore, intercropping boosted organic matter, available nitrogen (N), phosphorus (P), and potassium (K) in the tea rhizosphere. Enzyme activities, including acid phosphatase, alkaline phosphatase, urease, and β-glucosidase, were also elevated in tea/soybean intercropping. In soybean, shoot and root biomass, weight and number of nodules, and N, P, and K content increased over cultivation time. Correlation analysis showed that tea water extracts and polyphenols were positively linked to soil available P and alkaline phosphatase activities. Soybean root and nodule growth were correlated with soil N and P activation and tea water extracts, indicating that soybean-mediated underground interactions drive mineral nutrient mobilization in rhizosphere, further improving tea quality. This study provides mechanistic insights into tea/soybean intercropping, offering practical implications for sustainable tea cultivation practices. Full article

The root conformation of soybean is critical to achieve physiological activities such as nodulation and nitrogen fixation; however, the molecular determinants behind genotypic differences in its early development remain poorly described. In this study, we compared the characteristics of the soybean varieties HN75 and HN76 and examined developmental disparities in their root architectural characteristics and the transcriptomic profiles of radicles between them. The plant height and 100-grain weight of HN75, which had a longer growth cycle of 170 days, were slightly higher than those of HN76, which had a shorter growth cycle of 120 days. However, the numbers of pods and grains per plant were slightly lower. In terms of quality traits, HN75 had a higher oil content (23.40% versus 21.50%), whereas HN76 had a higher protein content (41.39% versus 35.71%). HN75 exhibited markedly superior root elongation (13.27 cm versus 10.15 cm), enhanced lateral root proliferation, and significantly greater nodule formation (19.53 versus 8.60 nodules per plant) relative to HN76 at 30 days post-germination, notwithstanding comparable nodule biomass. Chronobiological analysis (0–96 h post-germination) identified a pivotal developmental window of 48–72 h post-germination. Transcriptomic profiling of radicle tissues revealed 4792 differentially expressed genes (DEGs) in HN75 compared to 896 in HN76 during this critical interval, indicating substantially heightened transcriptional activity in HN75. Functional annotation enrichment demonstrated that HN75 DEGs were significantly enriched in phytohormone signalling cascades and isoprenoid biosynthetic pathways, whereas HN76 DEGs were predominantly associated with protein processing within the endoplasmic reticulum. We screened for eight genes (Glyma 10G071400, Glyma 13G057500, Glyma 08G016900, Glyma 09G028000, Glyma 18G265800, Glyma 03G032800, Glyma 02G064100, and Glyma 01G238600) that may play a role in the critical period of radicle development by performing network analyses and verified their dramatic changes in expression during this period by qRT-PCR. These results elucidate varietal-specific physiological and molecular mechanisms governing early radicle development in soybeans. These findings unravel mechanisms governing leguminous radicle development while establishing molecular blueprints for engineering cultivation protocols that would enhance soybean sustainability in edaphically constrained environments. Full article