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Keywords = acid soil

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19 pages, 6300 KB  
Article
Synergistic Effects of Biodegradable Nano-Plastics and Salt Stress on Maize Seedling Growth and Physiology
by Yuyang Li, Huiying Li, Chunfeng Xie, Zhuangzhuang Hong, Jing Liu, Shuaijie Jin, Yan Chen, Yunlu Wang, Zhanqiang Ma, Aneela Younas, Muhammad Shaaban, Yanfang Wang and Ling Liu
Agronomy 2026, 16(12), 1207; https://doi.org/10.3390/agronomy16121207 (registering DOI) - 21 Jun 2026
Abstract
The accumulation of polylactic acid nano-plastics (PLA-NPs) in saline–alkali soils poses a potential threat to crop growth; however, the underlying toxicological mechanisms remain poorly understood. We conducted a hydroponic experiment to investigate the effects of polylactic acid (PLA) NPs (100 and 500 mg [...] Read more.
The accumulation of polylactic acid nano-plastics (PLA-NPs) in saline–alkali soils poses a potential threat to crop growth; however, the underlying toxicological mechanisms remain poorly understood. We conducted a hydroponic experiment to investigate the effects of polylactic acid (PLA) NPs (100 and 500 mg L−1) under conditions both in the presence (50 mmol L−1 NaCl) and absence of salt stress on maize seed germination, seedling growth, physiological characteristics, and transcriptomic responses. The results showed that exposure to PLA-NPs, particularly at a high concentration (500 mg L−1), significantly inhibited seed germination and seedling growth. Compared to the low concentration (100 mg L−1) of PLA-NPs, the high concentrations (500 mg L−1) reduced the germination percentage by 25.0% and fresh weight by 25.8% and increased root MDA (6.7%), SOD (30.0%), POD (6.3%), ASA (13.4%), and GSH (13.1%). Under the same concentration of the PLA, PLA + NaCl treatments exerted stronger inhibitory effects than PLA-NPs alone, with the seed germination percentage and fresh weight reduced by an average of 52.7% and 6.6%, respectively. Notably, the inhibitory effects and integrated biomarker response (IBR) index of the PLA 500 + NaCl treatment were the highest. The presence of PLA-NPs in roots was confirmed using confocal laser scanning microscopy. GO enrichment analysis showed that pathways related to nutrient reservoir activity, oxidoreductase activity, hydrogen peroxide catabolic process, and hydrogen peroxide metabolic process were enriched under PLA-NP and PLA + NaCl treatments. KEGG analysis further indicated enrichment in phenylpropanoid biosynthesis, ABC transporters, and alpha-linolenic acid metabolism. The PLA-NP and PLA + NaCl treatments upregulated genes associated with oxidoreductase activity (Zm00001eb238800, Zm00001eb128620, and Zm00001eb020790). These findings suggest that synergistic toxicity of PLA-NPs and salinity stress in maize is primarily driven by the internalization of PLA-NPs and Na+ within maize roots, which negatively impacts maize seed germination and seedling growth by disrupting redox homeostasis and metabolic balance, thereby forcing plants to reallocate resources from growth toward oxidative stress defense. This study provides critical insights into the environmental risks of biodegradable nano-plastics in saline–alkali soil environments. Full article
(This article belongs to the Special Issue Legacy of Traditional Maize: Resilience, Quality and Lost Genes)
34 pages, 4538 KB  
Article
Molecular Characterization of Plant Growth-Promoting Bacteria Associated with Opuntia dillenii (Ker Gawl.) Haw (Cactaceae) in the Coastal Zone of Benin
by Yves Kévin Brun, Agossou Damien Pacôme Noumavo, Julien Colombet, Etienne Bankolé Atchadé, Lamine Baba-Moussa and François Lefort
Microorganisms 2026, 14(6), 1376; https://doi.org/10.3390/microorganisms14061376 (registering DOI) - 21 Jun 2026
Abstract
Cacti thrive in arid and coastal environments partly through associations with beneficial endophytic and rhizosphere bacteria; however, current knowledge remains limited. This study aimed to assess the diversity of cultivable bacteria associated with Opuntia dillenii and evaluate their potential as Plant Growth-Promoting (PGP) [...] Read more.
Cacti thrive in arid and coastal environments partly through associations with beneficial endophytic and rhizosphere bacteria; however, current knowledge remains limited. This study aimed to assess the diversity of cultivable bacteria associated with Opuntia dillenii and evaluate their potential as Plant Growth-Promoting (PGP) agents. Endophytic bacteria were isolated from cladodes and roots, while rhizobacteria were recovered from rhizosphere soil. Bacterial isolates were identified using morphological characteristics and 16S rRNA/gyrB sequencing, followed by screening for PGP traits, pH and temperature tolerance. A total of 31 isolates were obtained, including 23 endophytes and 8 rhizobacteria, mainly affiliated with Firmicutes, Actinobacteria, and Proteobacteria. Bacillus (35.48%) and Priestia (32.25%) predominated, with Priestia flexa as the most prevalent species. The most frequent PGP traits were phosphate solubilization (80.65%), proteolytic activity (70.97%), siderophore production (67.74%), and nitrogenase activity (64.52%). The highest phosphate solubilization indices were observed for strain R3 (3.41), R6 (3.39) and S6 (3.21), whilst the highest indole-3-acetic acid yields were recorded for C9 (172.88 µg/mL), R11 (96.22 µg/mL) and C3 (90.94 µg/mL), and the strongest siderophore production for C3 (30.37 mm), C7 (27.96 mm) and S7 (27.88 mm). These findings highlight O. dilleniid-associated coastal bacteria as promising resources for plant growth and plant stress resilience. Full article
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21 pages, 8642 KB  
Article
Enhancing Phosphorus Availability Through Bagasse Biochar Addition and Changes in phoD Bacterial Communities of Karst and Non-Karst Forest Soils
by Yanjun Chen, Xinyu He, Yueming Liang, Fujing Pan, Cheng Zeng, Haijun Tan, Qiang Li and Zeyan Wu
Microorganisms 2026, 14(6), 1373; https://doi.org/10.3390/microorganisms14061373 (registering DOI) - 21 Jun 2026
Abstract
Biochar can enhance microbial-mediated organic phosphorus mineralization, but the underlying mechanisms remain unknown in forest soils with varying pH values. An incubation experiment was conducted using karst (alkaline) and non-karst (acidic) forest soils. Four amounts of bagasse biochar were applied (0, 5, 10, [...] Read more.
Biochar can enhance microbial-mediated organic phosphorus mineralization, but the underlying mechanisms remain unknown in forest soils with varying pH values. An incubation experiment was conducted using karst (alkaline) and non-karst (acidic) forest soils. Four amounts of bagasse biochar were applied (0, 5, 10, and 15 t·hm−2) to assess their effects on soil phosphorus availability and microbial community structure. Olsen-P content of alkaline and acidic forest soils increased with increasing bagasse biochar addition and incubation time, especially in non-karst forest soil. The structure and diversity of phoD-harboring bacterial community of acidic forest soil were significantly altered by the amount of bagasse biochar added and the incubation time, whereas those in alkaline karst forest soil were not significantly affected. The relative abundance of the dominant order Burkholderiales reached (43%) in acidic forest soil, significantly exceeding the (9%) recorded in alkaline karst forest soil. The phoD bacteria in acidic forest soil had more complex microbial networks and were more closely related to phosphorus fractions than those in alkaline forest soil. Structural equation modeling indicated that soil phosphorus availability was directly controlled by bagasse biochar input in acidic forest soil, with an indirect pathway linked to phoD bacterial community structure. The contribution of phoD bacteria to the variation in phosphorus availability was higher in acidic forest soil than in alkaline forest soil based on variance partitioning, indicating that enhancing soil phosphorus availability with bagasse biochar depends on the amount added, soil type, and its regulation of phoD bacterial communities. Full article
(This article belongs to the Special Issue Soil Microbial Carbon/Nitrogen/Phosphorus Cycling: 2nd Edition)
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20 pages, 1741 KB  
Article
In Vitro, In Silico, and In Vivo Evaluation of Antiplasmodial Activity of Ursodeoxycholic Acid Following GNPS Dereplication of an Active Streptomyces sp. Fraction
by Nanang R. Ariefta, Baldorj Pagmadulam, Takako Aboshi and Yoshifumi Nishikawa
Pharmaceuticals 2026, 19(6), 958; https://doi.org/10.3390/ph19060958 (registering DOI) - 20 Jun 2026
Abstract
Background/Objectives: The emergence of drug-resistant Plasmodium falciparum highlights the need for new antiplasmodial compounds with distinct mechanisms of action. Microbial secondary metabolites, particularly from Streptomyces species, remain important sources of bioactive molecules. This study aimed to evaluate antiplasmodial metabolites associated with a Mongolian [...] Read more.
Background/Objectives: The emergence of drug-resistant Plasmodium falciparum highlights the need for new antiplasmodial compounds with distinct mechanisms of action. Microbial secondary metabolites, particularly from Streptomyces species, remain important sources of bioactive molecules. This study aimed to evaluate antiplasmodial metabolites associated with a Mongolian Streptomyces isolate. Methods: Streptomyces sp. strain D10 was isolated from Mongolian soil samples and extracted with ethyl acetate. Bioassay-guided fractionation was performed, followed by LC–HRMS analysis and GNPS-based spectral dereplication. Antiplasmodial activity was evaluated against P. falciparum 3D7, K1, and Dd2 strains using a SYBR Green I assay. Cytotoxicity was assessed in HSF cells. Stage-specific susceptibility assays were conducted using synchronized 3D7 parasites. Comparative docking analyses against β-hematin and the chloroquine resistance transporter (PfCRT), together with target prediction and molecular docking analyses, were performed to explore potential mechanisms. In vivo efficacy was evaluated using a Plasmodium yoelii 17XNL mouse model. Results: Fractionation yielded an active fraction (C2), and LC–HRMS and GNPS-based dereplication suggested a bile acid-like metabolite, with ursodeoxycholic acid (UDCA) returned as a putative spectral library candidate associated with fraction C2. Fraction C2 and UDCA showed comparable antiplasmodial activity against P. falciparum 3D7 (IC50 = 6.55 ± 3.00 and 4.68 ± 0. 65 µg/mL, respectively) without detectable cytotoxicity up to 200 µg/mL. Activity was retained against multidrug-resistant K1 and Dd2 strains. Stage-specific assays demonstrated inhibitory activity across ring, trophozoite, and schizont stages without significant stage-dependent differences. Comparative docking analyses suggested interaction profiles distinct from chloroquine in β-hematin and PfCRT models. Additional docking analyses identified PfGluPho, PfMAPK, and PfPFT-β as potential targets. In vivo, UDCA reduced parasitemia in a dose-dependent manner without significant toxicity. Conclusions: UDCA exhibited moderate antiplasmodial activity across in vitro, in silico, and in vivo evaluations with a favorable selectivity profile, supporting further investigation of bile acid-like metabolites as potential antimalarial scaffolds. Full article
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25 pages, 58208 KB  
Article
Soil Geochemistry and Exploration Implications of the Terziali Gold Prospect (Central Anatolia, Türkiye): A Case Study of Shear-Related Orogenic Gold Mineralization
by Özgür Sapancı, Nezihi Köprübaşı, Necla Köprübaşı, Olgun Duru, Yunus Emre Ekim and Emin Çiftci
Minerals 2026, 16(6), 649; https://doi.org/10.3390/min16060649 (registering DOI) - 19 Jun 2026
Abstract
The Terziali is a shear-hosted orogenic gold prospect located in the Central Anatolian Crystalline Complex, Türkiye. This study focuses on soil geochemistry, element correlations, background and threshold values, and evaluates exploration implications over a survey area of 35.5 km2. A total [...] Read more.
The Terziali is a shear-hosted orogenic gold prospect located in the Central Anatolian Crystalline Complex, Türkiye. This study focuses on soil geochemistry, element correlations, background and threshold values, and evaluates exploration implications over a survey area of 35.5 km2. A total of 1826 soil samples were collected from the B horizon using a grid of 100 × 50 m and were analyzed using ICP-AES, ICP-MS, and fire assay techniques. Statistical techniques of median + 2MAD threshold calculations, descriptive statistics, Kolmogorov–Smirnov tests, correlation analysis, hierarchical clustering, and Q–Q plots were carried out to identify geochemical anomalies. The data demonstrate Au threshold (28 ppb) and peak concentration (460 ppb), non-normal distributions characterized by strong positive skewness, revealing the outliers linked to mineralization. Soil geochemistry indicates a moderate association between Au and As in the four-acid dataset (r = 0.465), although the correlations between Au and Sb and Ag and W are relatively weak. The spatial analysis indicates that Au anomalies are predominantly linked to the NW–SE-oriented Demirli Thrust Fault. As displays extensive dispersion halos surrounding the gold anomalies; it establishes itself as an efficient pathfinder element. Conversely, Sb and W exhibit unique anomaly patterns, whereas Ag patterns are weak and dispersed. The Terziali prospect provides a substantial geochemical framework for identifying structurally controlled orogenic gold systems in Central Anatolia and the western Tethyan metallogenic belt. Full article
24 pages, 12735 KB  
Article
Fulvic Acid Influence on Arsenic Immobilization During Jarosite Bioreduction and Transformation
by Yi Shan, Wei-Xi Huang, Hong-Chang Liu, Zhen-Yuan Nie and Jin-Lan Xia
Minerals 2026, 16(6), 648; https://doi.org/10.3390/min16060648 (registering DOI) - 19 Jun 2026
Abstract
Acid mine drainage (AMD) is enriched with arsenite (As(III)), arsenate (As(V)), and jarosite. While jarosite can immobilize arsenic (As) through adsorption and other mechanisms, it dissolves and transforms into other minerals under near-neutral and reducing conditions via microbial mediation, thereby altering As fate. [...] Read more.
Acid mine drainage (AMD) is enriched with arsenite (As(III)), arsenate (As(V)), and jarosite. While jarosite can immobilize arsenic (As) through adsorption and other mechanisms, it dissolves and transforms into other minerals under near-neutral and reducing conditions via microbial mediation, thereby altering As fate. Fulvic acid (FA), a ubiquitous natural organic matter in the environment, has been proven to exhibit complex interactions with various iron minerals, Fe/S-metabolizing microorganisms, and As. However, the role of FA in the bioreduction and transformation of jarosite, as well as its subsequent impact on As mobility and fate, remains unclear. This study aims to elucidate the regulatory effect of FA on the biodissolution and transformation of jarosite, and the corresponding changes in As speciation. The results showed that FA exerted contrasting effects depending on arsenic speciation. In the As(III) treatments, FA intensified the inhibition of microbial dissimilatory sulfate reduction, suppressed sulfide production, and consequently limited orpiment formation. In contrast, in the As(V) treatments, FA enhanced the association of As(V) with jarosite surfaces, reduced aqueous As stress, and supported the persistence of As-tolerant sulfate-reducing populations. This promoted jarosite transformation toward mackinawite and facilitated As immobilization through orpiment precipitation. This study reveals the critical role of FA in the migration and transformation of As in mining areas, providing novel insights for optimizing AMD remediation strategies such as soil capping. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
29 pages, 6588 KB  
Article
Effect of Biodegradable PLA-Based and Conventional LDPE Mulch Films on Pathogenic and Functional Soil Microbial Communities
by Magdalena Zaborowska, Jadwiga Wyszkowska, Agata Borowik and Jan Kucharski
Int. J. Mol. Sci. 2026, 27(12), 5530; https://doi.org/10.3390/ijms27125530 (registering DOI) - 18 Jun 2026
Viewed by 48
Abstract
Plastics and microplastics are widespread in the environment, yet knowledge about their impact on agricultural soils, including their microbiological properties, remains limited. Therefore, this study addressed the research question regarding the impact of secondary microplastics, biodegradable poly(lactic acid) (PLA) mulch film, and low-density [...] Read more.
Plastics and microplastics are widespread in the environment, yet knowledge about their impact on agricultural soils, including their microbiological properties, remains limited. Therefore, this study addressed the research question regarding the impact of secondary microplastics, biodegradable poly(lactic acid) (PLA) mulch film, and low-density polyethylene (LDPE) film on the abundance, structure, and functions of soil bacteria, with particular emphasis on the presence of bacterial pathogens. PLA and LDPE were applied to the soil at a dose of 4 g kg−1 d.m. of soil. The aim of the experiment was to evaluate and compare the effectiveness of soil bioaugmentation with the Pseudomonas umsongensis strain and its biostimulation with humic acids in mitigating the negative effects of microplastics. The response of culturable bacteria revealed high sensitivity of organotrophic bacteria to both microplastics, with a stronger inhibitory effect from PLA, as well as stimulation of actinomycetes. 16S rRNA gene amplicon sequencing indicated that the materials differentially influenced the bacterial response. PLA most strongly stimulated Actinobacteriota and favored the dominance of Bacillus and Limnochorda, whereas LDPE promoted the growth of Actinobacteriota and Chloroflexota as well as genera KD4-96 and 1921-2. Both microplastics were colonized by potential pathogens, including Bacillus, Mycobacterium, Ralstonia, and Cupriavidus. PLA additionally stimulated the proliferation of Leifsonia sp. and Curtobacterium sp., while both PLA and LDPE reduced the abundance of Enterobacter sp. and Herbaspirillum sp. Bioaugmentation using the Pseudomonas umsongensis strain was more effective in restoring the balance of the soil microbiome than biostimulation with humic acids. The results indicate that microbial preparations based on Pseudomonas umsongensis may serve as an important tool in restoring the balance of soil exposed to microplastics. Full article
(This article belongs to the Special Issue Environmental Microorganisms and Pathogen Infections)
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28 pages, 1832 KB  
Article
Analysis of the Chemical and Radiological Risks Associated with Wastes from Mining in the Iberian Pyrite Belt
by Juan Antonio Ramírez-Pérez, Manuel Jesús Gázquez-González, Felipe Jesús González-Barrionuevo and Juan Pedro Bolívar
Minerals 2026, 16(6), 645; https://doi.org/10.3390/min16060645 (registering DOI) - 18 Jun 2026
Viewed by 46
Abstract
Mining activities in the Iberian Pyrite Belt have generated large volumes of legacy wastes that may pose both environmental and radiological concerns, potentially limiting their reuse and valorization. However, integrated assessments combining chemical, mineralogical, and radiological characterization of these materials remain scarce. In [...] Read more.
Mining activities in the Iberian Pyrite Belt have generated large volumes of legacy wastes that may pose both environmental and radiological concerns, potentially limiting their reuse and valorization. However, integrated assessments combining chemical, mineralogical, and radiological characterization of these materials remain scarce. In this work, representative mining wastes from twelve sites across the Iberian Pyrite Belt were investigated through X-ray fluorescence, X-ray diffraction, scanning electron microscopy, standardized leaching tests, alpha and gamma spectrometry, and radon emanation measurements. The results revealed significant enrichment in potentially toxic elements, particularly Cu, Zn, Pb, and As, with concentrations exceeding local soil background values by up to several orders of magnitude. Leaching tests identified oxidized sulfide-rich residues as the materials with the highest pollutant mobility and greatest acid-generating potential. In contrast, radiological characterization showed that uranium-series, thorium-series radionuclides, and 40K activities, together with radiological hazard indices and radon exhalation rates, were generally comparable to those of surrounding natural soils and remained below internationally recommended limits. These findings indicate that chemical contamination represents the main environmental constraint of these wastes, whereas radiological impact is generally low, supporting their case-by-case evaluation for remediation, valorization, and potential exclusion from radiological control. Full article
17 pages, 9118 KB  
Article
Physiological and Multi-Omics Insights into Drought Adaptation of Poacynum hendersonii Seedlings Under Different Water Deficit Regimes
by Yongqian Jia, Ya Ding, Qian Wu, Yuehua Yu, Zhiyi Cheng, Zhongwei Wang and Hao Ma
Agronomy 2026, 16(12), 1191; https://doi.org/10.3390/agronomy16121191 - 18 Jun 2026
Viewed by 109
Abstract
This study used Poacynum hendersonii (Hook. f.) Woods. seedlings as experimental material. A soil drought group (gradual soil drying) and a PEG-simulated drought group (15% PEG-6000 treatment) were established. By combining physiological measurements, metabolomics, and transcriptomics, we investigated the physiological and molecular mechanisms [...] Read more.
This study used Poacynum hendersonii (Hook. f.) Woods. seedlings as experimental material. A soil drought group (gradual soil drying) and a PEG-simulated drought group (15% PEG-6000 treatment) were established. By combining physiological measurements, metabolomics, and transcriptomics, we investigated the physiological and molecular mechanisms of P. hendersonii in response to drought stress. The results showed that under drought stress, P. hendersonii alleviated oxidative damage by activating the antioxidant enzyme system (catalase, CAT; superoxide dismutase, SOD; peroxidase, POD), and enzyme activities recovered significantly after rehydration. In the osmotic stress group (PEG), hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents increased significantly in the later stages, whereas membrane damage was milder in the soil drought group. Metabolomics analysis revealed significant enrichment of starch and sucrose metabolism pathways during early drought, shifting to unsaturated fatty acid biosynthesis and carbon metabolism in later stages. PEG-simulated drought specifically induced the accumulation of arachidonic acid, which may be associated with ferroptosis-like processes, although direct evidence is lacking. Transcriptomics analysis identified 23,623 differentially expressed genes (DEGs), with transcription factor families such as bHLH, MYB, and NAC playing key roles in drought response. Weighted Gene Co-expression Network Analysis (WGCNA) further revealed gene modules significantly correlated with physiological traits, indicating that enhanced respiratory metabolism (glycolysis, tricarboxylic acid (TCA) cycle) is an important strategy for P. hendersonii to adapt to drought. The study also found that while PEG-simulated drought could simulate the physiological effects of soil drought, significant differences existed in molecular pathways, particularly during later stress stages. This research provides a theoretical basis for elucidating the drought resistance mechanisms of P. hendersonii and offers potential targets for crop drought resistance breeding. Full article
(This article belongs to the Section Plant-Crop Biology and Biochemistry)
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17 pages, 2733 KB  
Article
Combined Mechanisms of Streptomyces sp. HU2014 and Coronatine in Promoting Maize Seedling
by Linfeng Hu, Xiaoyu Wang, Jiangsheng Meng, Qian Su, Wenhui Shi, Jungao Zhang and Hongxia Zhu
Microorganisms 2026, 14(6), 1361; https://doi.org/10.3390/microorganisms14061361 - 17 Jun 2026
Viewed by 183
Abstract
The rhizosphere microbiome and phytohormone signaling are critical determinants of plant growth and stress resilience. This study evaluated the combined effects of Streptomyces sp. HU2014 and coronatine (COR) on maize (Zea mays L.) seedlings. Four treatments were established: control (CK), COR seed [...] Read more.
The rhizosphere microbiome and phytohormone signaling are critical determinants of plant growth and stress resilience. This study evaluated the combined effects of Streptomyces sp. HU2014 and coronatine (COR) on maize (Zea mays L.) seedlings. Four treatments were established: control (CK), COR seed soaking (Cor), HU2014 soil inoculation (S), and combined S + Cor (SCor). Growth parameters, chlorophyll content, and antioxidant/oxidative stress markers were measured, and root and leaf transcriptomes, together with root metabolomes, were compared between SCor and CK, followed by qRT-PCR validation. Compared with CK, SCor treatment significantly increased stem diameter (~60%), plant height (~20%), and relative chlorophyll content (SPAD, ~50%). Soluble sugar levels were elevated by over 40% in both leaves and roots, accompanied by tissue-specific modulation of antioxidant enzymes. Transcriptomic analysis of SCor vs. CK revealed 2459 differentially expressed genes (DEGs) in leaves and 3444 DEGs in roots; leaves exhibited upregulation of photosynthetic pigment metabolism (porphyrin and carotenoid pathways) and volatile defense compounds (alkaloids and monoterpenoids), whereas roots showed enrichment in phenylpropanoid/flavonoid biosynthesis, benzoxazinoid synthesis, and starch/sucrose metabolism. Metabolomics of SCor vs. CK identified 526 differentially accumulated metabolites (DAMs) in roots, with significant enrichment in aminoacyl-tRNA biosynthesis, phenylalanine metabolism, and linoleic acid metabolism. Integrative multi-omics analysis further revealed that the JA precursor 13-epi-12-oxo-phytodienoic acid co-clustered with stress-responsive transcription factors (e.g., DREB1C), while tricarboxylic acid (TCA) intermediates and phenylpropanoid metabolites were linked to energy and lignin biosynthesis genes. qRT-PCR confirmed the expression trends of 14 out of 15 tested genes. Collectively, combined HU2014 and COR application triggers tissue-specific transcriptional and metabolic reprogramming in maize, coupling JA-mediated stress signaling with enhanced carbon metabolism and secondary defense compound synthesis to promote rhizosphere adaptation and seedling vigor. Full article
(This article belongs to the Section Plant Microbe Interactions)
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22 pages, 2089 KB  
Article
Field Epidemiology of Huanglongbing: High Psyllid Density, Disease Severity, and an Alternative Host in Northern Thailand
by Jiraporn Sangta, Tibet Tangpao, Kanyakorn Piraonapicha, Kawiporn Chinachanta, Chetsada Chainanti, Tuan Nguyen and Sarana Rose Sommano
Crops 2026, 6(3), 58; https://doi.org/10.3390/crops6030058 - 17 Jun 2026
Viewed by 272
Abstract
This study investigated the epidemiology and incidence of citrus Huanglongbing (HLB) disease in citron (Citrus medica L.) under varying field conditions. This research specifically aimed to quantify disease severity, assess populations of the primary vector, the Asian citrus psyllid (Diaphorina citri [...] Read more.
This study investigated the epidemiology and incidence of citrus Huanglongbing (HLB) disease in citron (Citrus medica L.) under varying field conditions. This research specifically aimed to quantify disease severity, assess populations of the primary vector, the Asian citrus psyllid (Diaphorina citri), and identify potential alternative host plants sustaining the vector and the pathogen. Field surveys were executed across three sites characterised by distinct elevations and management practices. Site-level soil nutrient profiles exhibited moderate acidity (pH 4.67–5.74) and significant differences in organic matter and nitrogen. These findings suggest that localised deficiencies in calcium and boron may exacerbate disease severity, contributing to the varied epidemiological patterns observed across sites. Analysis revealed that both HLB disease severity and D. citri population density were significantly influenced by altitude, field condition, and orchard management. The low-elevation site (860 m above sea level (ASL)), characterised by poor maintenance, exhibited the highest mean psyllid populations (averaging 13 individuals per sticky trap per day) and the most severe disease symptoms. Conversely, the high-elevation site (1674 m ASL) displayed significantly lower infection rates and healthier tree conditions. Symptomatic citron trees across all sites consistently exhibited characteristic HLB foliar and fruit symptoms (blotchy mottle and lopsided fruits). Quantitative Polymerase Chain Reaction (qPCR) successfully detected the causal agent, Candidatus Liberibacter asiaticus (CLas), in symptomatic citron samples from all locations, with the highest relative fold-change (2−ΔΔCt = 4628.24). Crucially, multiple developmental stages of D. citri were observed infesting the common weed Bidens pilosa. Furthermore, qPCR confirmed the presence of CLas DNA within the B. pilosa tissue itself (2−ΔΔCt = 210.84). This finding constitutes the first field-based evidence that B. pilosa can serve as a novel alternative host that supports both the D. citri vector and the CLas pathogen. These results establish citron as a highly susceptible host and identify B. pilosa as a new, critical epidemiological link in the HLB transmission cycle, thereby underscoring the necessity for integrated, landscape-level disease management strategies. Full article
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28 pages, 7880 KB  
Article
Bryophytes as Strong Aluminum Accumulators in Acidic Soils: Cell-Wall Binding and Physiological Tolerance Mechanisms
by Roghieh Hajiboland, Aiuob Moradi, Hedieh Majmoueh-Koub, Roser Tolrà, Ana Paravinja, Milos Stanojevic, Miroslav Nikolic and Charlotte Poschenrieder
Plants 2026, 15(12), 1877; https://doi.org/10.3390/plants15121877 - 17 Jun 2026
Viewed by 198
Abstract
Bryophytes are key components of acid–soil ecosystems; however, their capacity for aluminum (Al) accumulation and tolerance remains poorly understood. In this study, bryophytes and a limited number of pteridophyte and lichen species were collected from acidic soils of tea plantations and adjacent forest [...] Read more.
Bryophytes are key components of acid–soil ecosystems; however, their capacity for aluminum (Al) accumulation and tolerance remains poorly understood. In this study, bryophytes and a limited number of pteridophyte and lichen species were collected from acidic soils of tea plantations and adjacent forest stands in the Caspian region of northern Iran and analyzed. Nearly all bryophyte specimens exhibited Al concentrations above the critical accumulation threshold (1000 µg g−1 DW), with some reaching values exceeding 28,000 µg g−1 DW, confirming their strong accumulation capacity. After Al, iron was the most abundantly accumulated metal (1430–22,800 µg g−1 DW), followed by manganese (100–3100 µg g−1 DW). The sampled lichen species accumulated Al at concentrations between 1063 and 9154 µg g−1 DW, while Al levels in the aerial parts of pteridophytes rarely exceeded the critical threshold; when they did, accumulation occurred predominantly in old and fertile fronds rather than sterile ones. Three field-collected bryophyte species—Barbula unguiculata, Palamocladium euchloron, and Hypnum cupressiforme—were acclimated to laboratory conditions and treated with two Al levels (without or with 150 µM Al, pH 4.0) for 12 weeks. The leafy shoots were analyzed for their antioxidant response, osmolyte accumulation, phenolic metabolism, callose deposition, and carboxylic-acid profile. Histochemical analyses revealed predominant localization of Al in cell walls, associated with enrichment of pectin and uronic acids. These responses were most pronounced in H. cupressiforme, followed by P. euchloron, and least evident in B. unguiculata. Elevated levels of intracellular detoxification compounds—phenolics, flavonoids, and carboxylic acids (tartaric, oxalic, malic, and citric acids)—were detected, again with species-specific differences. Overall, the results reveal that bryophytes employ multiple physiological strategies to tolerate Al toxicity, with substantial interspecific variation. These findings emphasize their ecological significance and provide a foundation for future research on the physiological and evolutionary mechanisms underlying Al tolerance and accumulation in early land plants. Full article
(This article belongs to the Collection Bryophyte Biology)
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21 pages, 1141 KB  
Article
Plastic and Biodegradable Mulch Reshapes the Nitrogen Cycling Process in Soil
by Melinda Haydee Kovacs and Emoke Dalma Kovacs
Microplastics 2026, 5(2), 126; https://doi.org/10.3390/microplastics5020126 - 16 Jun 2026
Viewed by 86
Abstract
Background: Soil mulching is a widely adopted agricultural practice known to regulate soil microclimate and enhance crop productivity; yet the biochemical mechanisms by which intact plastic and biodegradable mulch films influence soil nitrogen (N) cycling at the metabolic pathway level remain largely unexplored. [...] Read more.
Background: Soil mulching is a widely adopted agricultural practice known to regulate soil microclimate and enhance crop productivity; yet the biochemical mechanisms by which intact plastic and biodegradable mulch films influence soil nitrogen (N) cycling at the metabolic pathway level remain largely unexplored. Understanding these nitrogen transformation pathways is critical for assessing the long-term impacts of mulching materials on soil microbial communities, soil health, and sustainable agricultural management. This study focuses on the biochemical effects of intact mulch film application on soil N metabolism. Methods: N cycle-related soil metabolites were profiled using GC‒MS/MS and MALDI TOF/TOF MS and then integrated with multivariate statistical modelling and pathway-level metabolic network perturbation analysis to compare conventional plastic and biodegradable plastic mulch film application against unmulched controls. Results: A panel of 62 KEGG-annotated N-cycle metabolites was profiled, and material-dependent metabolome separation was confirmed by OPLS-DA (R2Y 0.893–0.956; Q2 0.546–0.786). Both mulching materials significantly perturbed soil N-metabolite pools but differed in terms of pathway identity, magnitude, and directionality. Conventional plastic mulching caused the greatest disruption—near-complete suppression of N-storage and stress-adaptation pools (NES of −1.16; impact score of 10.01) and severe impairment of aspartate-centred metabolism—with L-aspartate identified as a critical stoichiometric hub. Biodegradable mulching material imposed a distinct profile dominated by inhibition of branched-chain amino acid catabolism and lysine degradation, with L-pipecolate as a treatment-specific critical impact node. Conclusions: These findings support that mulching material choice is a primary determinant of soil N-cycling biochemistry. The observed metabolite-level perturbations are suggestive of potential consequences for nitrogen retention. Though this inference is based on metabolite pool size differences and network topology metrics rather than directly measured process rates, it should therefore be interpreted with appropriate caution. Full article
22 pages, 1652 KB  
Article
Soil Physicochemical Parameters and Bibliographically Inferred Microbial Diversity as Drivers of Early-Stage Biodegradation of Colocasia esculenta and Manihot esculenta Starch Bioplastics in Three High-Andean Soils of Ecuador
by María Soledad Núñez Moreno, Georgina Esther Carmilema Yungan, María Gabriela Arias Garnica and David Esteban Puyol Guevara
Polymers 2026, 18(12), 1506; https://doi.org/10.3390/polym18121506 - 16 Jun 2026
Viewed by 241
Abstract
Single-use plastic residues persist in agricultural and peri-urban soils of the Ecuadorian Andes. Regionally sourced starch-based films are a plausible local replacement for short-lifetime petroleum plastics, yet field-relevant degradation data for tropical high-altitude soils remain scarce. This study evaluated the soil biodegradability of [...] Read more.
Single-use plastic residues persist in agricultural and peri-urban soils of the Ecuadorian Andes. Regionally sourced starch-based films are a plausible local replacement for short-lifetime petroleum plastics, yet field-relevant degradation data for tropical high-altitude soils remain scarce. This study evaluated the soil biodegradability of bioplastic films produced from Colocasia esculenta (malanga blanca) and Manihot esculenta (yuca) across three contrasting soils from Chimborazo, Ecuador (ESPOCH, San Andrés and Río Chimborazo; 2825–3249 m a.s.l.) as a function of their physicochemical properties and bibliographically inferred microbial context. The films were prepared by citric acid starch extraction, glycerol plasticization and carboxymethylcellulose reinforcement; the gravimetric weight loss was tracked on days 0, 11, 18, 27, 40 and 47 on n = 20–21 film replicates per soil × feedstock combination, with the soils characterized by their pH, electrical conductivity and organic matter. After 47 days, the malanga films reached 42.3 ± 13.6%, 22.9 ± 10.7% and 54.1 ± 19.3% mean (±standard deviation, SD) weight loss in the ESPOCH, San Andrés and Río Chimborazo soils, respectively; the yuca films reached 24.4 ± 6.5%, 21.1 ± 6.8% and 49.4 ± 18.7%. The between-soil differences were statistically significant at 47 days according to the analysis of variance (ANOVA) (malanga: F = 22.17, p < 0.001; yuca: F = 34.08, p < 0.001; Tukey’s Honestly Significant Difference (HSD)), with the results corroborated by the Kruskal–Wallis method (H = 29.16 and 37.05; both p < 0.001), given the partial departure from normality identified by the Shapiro–Wilk test. The ordering of degradation departed from the bulk organic matter ranking, indicating that microbial community composition, rather than organic matter quantity alone, was the proximal driver. These findings extend the scarce evidence base on cassava/taro film degradation under high-Andean conditions. Full article
(This article belongs to the Section Biobased and Biodegradable Polymers)
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34 pages, 14526 KB  
Review
From Infection to Adaptation: Sclerotium rolfsii-Induced Stress and Defense in Tomato
by Suvankar Kumar Biswas, Touhidur Rahman Anik, Shanta Adhikary, Mrinmoy Kundu, Farjana Sultana, Mohamamd Golam Mostofa and Md. Motaher Hossain
Stresses 2026, 6(2), 35; https://doi.org/10.3390/stresses6020035 - 15 Jun 2026
Viewed by 292
Abstract
Tomato (Solanum lycopersicum) is a globally important horticultural crop, with Asia contributing 60.45% of total production, followed by the Americas at 13.36%. Tomato productivity is increasingly constrained by southern blight, a destructive disease responsible for yield losses ranging from 30 to [...] Read more.
Tomato (Solanum lycopersicum) is a globally important horticultural crop, with Asia contributing 60.45% of total production, followed by the Americas at 13.36%. Tomato productivity is increasingly constrained by southern blight, a destructive disease responsible for yield losses ranging from 30 to 90% and annual economic damage of $10–20 million. The causal pathogen, Sclerotium rolfsii, infects the stem base and induces reddish-brown cankers through secretion of oxalic acid (OA) and cell wall-degrading enzymes, which girdle tissues, impair water transport, and result in rapid plant wilting and death. Its persistence in soil via sclerotia, broad host range, and adaptability make the disease difficult to manage. Recent advances in genomics, transcriptomics, proteomics and other multi-omics approaches have substantially improved understanding of pathogen virulence factors, host defense responses and disease epidemiology. These studies have revealed key roles of OA, carbohydrate-active enzymes, effector proteins, and sclerotial melanization in pathogenesis, while highlighting the activation of salicylic acid (SA)-, jasmonic acid (JA)-, and ethylene (ET)-mediated defense pathways in tomato. Although cultural, biological, and chemical measures are available, these measures often provide inconsistent protection when used alone. Promising strategies include the use of biocontrol agents, hypovirulence-inducing mycoviruses, and chemical fungicides such as carboxamides and quinone outside inhibitors (QoIs), though fungicide resistance remains a risk factor. Integrated Disease Management (IDM) approaches, such as combining biocontrol agents with fungicides, demonstrate enhanced efficacy. This review also evaluates progress in resistance breeding, grafting, RNA interference (HIGS and SIGS), CRISPR-based genome editing, and exploitation of wild genotypes for durable resistance. Furthermore, emerging precision agriculture tools, including hyperspectral imaging, machine learning-assisted disease detection and climate-resilient management strategies, were discussed as new components of sustainable disease management. Full article
(This article belongs to the Section Plant and Photoautotrophic Stresses)
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