Antifungal Activity of Copper Oxide Nanoparticles against Root Rot Disease in Cucumber

A deep learning-based approach for the detection of cucumber diseases

Cucumbers play a significant role as a greenhouse crop globally. In numerous countries, they are fundamental to dietary practices, contributing significantly to the nutritional patterns of various populations. Due to unfavorable environmental conditions, they are highly vulnerable to various diseases. Therefore the accurate detection of cucumber diseases is essential for maintaining crop quality and ensuring food security. Traditional methods, reliant on human inspection, are prone to errors, especially in the early stages of disease progression. Based on a VGG19 architecture, this paper uses an innovative transfer learning approach for detecting and classifying cucumber diseases, showing the applicability of artificial intelligence in this area. The model effectively distinguishes between healthy and diseased cucumber images, including Anthracnose, Bacterial Wilt, Belly Rot, Downy Mildew, Fresh Cucumber, Fresh Leaf, Pythium Fruit Rot, and Gummy Stem Blight. Using this novel approach, a balanced accuracy of 97.66% on unseen test data is achieved, compared to a balanced accuracy of 93.87% obtained with the conventional transfer learning approach, where fine-tuning is employed. This result sets a new benchmark within the dataset, highlighting the potential of deep learning techniques in agricultural disease detection. By enabling early disease diagnosis and informed agricultural management, this research contributes to enhancing crop productivity and sustainability.

Coating Seeds with Paenibacillus polymyxa ZF129 Microcapsule Suspension Enhanced Control Effect on Fusarium Root Rot and Promoted Seedling Growth in Cucumber

Fusarium root rot, a destructive soil-borne fungal disease, necessitates eco-friendly biocontrol strategies. This study developed a microbial seed-coating approach using the antagonistic strain Paenibacillus polymyxa ZF129, formulated into a microencapsulated powder (108 CFU/g) and a suspension (CS-ZF129). CS-ZF129 application enhanced cucumber resistance, achieving 46.30 ± 0.02% disease suppression while promoting root growth. The maximum increase in the fresh weight of the root in the promotion of rectangular growth was 47.16%. The colonization dynamics of ZF129 in the rhizosphere were systematically tracked, revealing its antagonistic correlation with Fusarium proliferation. An enzymatic activity analysis further uncovered the underlying regulatory mechanisms, demonstrating induced defense responses through pathogenesis-related protein activation. These findings highlight ZF129's dual functionality as a biocontrol agent and a plant growth promoter, offering a sustainable strategy against soil-borne pathogens.

Toxicity of copper oxide nanoparticles in barley: induction of oxidative stress, hormonal imbalance, and systemic resistances

BACKGROUND

Over the years, nanoparticles have emerged as a promising approach for improving crop growth, yield, and overall agricultural sustainability. However, there has been growing concern about the potential adverse effects of nanoparticles in the agricultural sector and the environment. The present study aimed to investigate the detrimental effects of high (1000 mg L-1) concentrations of copper oxide nanoparticles (CuO NPs) on barley seedlings. The equivalent concentrations of CuO bulk and the ionic form of copper were also used in the experiments for comparative analysis. CuO NPs were characterized by Field Emission-Scanning Electron Microscopy, Dynamic Light Scattering, Zeta Potential analysis, and X-ray Diffraction prior to the application. Barley seedlings were subjected to the foliar application of CuO NP, CuO bulk, ionic Cu, and control group. The presence of CuO NPs in barley leaves was confirmed 72 hours after treatment by energy-dispersive X-ray analysis.

RESULTS

The results showed a CuO NPs treatment led to an impairment of nutrient balance in barley leaves. An increase in hydrogen peroxide content followed by the higher specific activity of catalase and ascorbate peroxidase was also observed in response to CuO NPs, CuO bulk, and Cu2+ ions. The profile of phytohormones including auxins (IAA and IBA), Gibberellins (GA1, GA4, and GA9), abscisic acid (ABA), ethylene (ET), and jasmonic acid (JA) significantly affected by CuO NPs, CuO bulk, and Cu2+ ions. The transcripts of the PR1 gene involved in systemic acquired resistance (SAR) and LOX-1 and PAL involved in induced systemic resistance (ISR) were significantly upregulated in response to CuO NPs treatment.

CONCLUSION

Our findings suggest that the systemic resistances in barley seedlings were induced by higher accumulation of ABA, ET, and JA under CuO NPs treatment. The activation of systemic resistances indicated the involvement of both SAR and SAR pathways in the response to CuO NPs in barley.

One-Pot Synthesis and Characterization of Magnetic α-Fe2O3/CuO/CuFe2O4 Nanocomposite for Multifunctional Therapeutic Applications

This study demonstrates a novel nanostructured drug delivery system utilizing α-Fe2O3/CuO/CuFe2O4 ternary nanocomposite for effective drug transport in sick tissues. Centella Asiatica plant extract was employed to synthesize the Fe2O3/CuO/CuFe2O4 nanocomposite via sol-gel auto combustion technique. The structural and morphological characteristics of the nanocomposite were investigated by XRD, FT-IR, SEM, EDX, and VSM for magnetic properties. The XRD analysis demonstrates the successful synthesis of Fe2O3/CuO/CuFe2O4 nanocomposite with an average crystallite size of 18.393 nm. The antioxidant and antifungal capabilities of this nanocomposite were assessed for its biological activity. A notable inhibitory zone was observed when tested against the Alternaria spp. and Bipolaris sorokiniana fungi. An IC50 value of 109.88 μg/ml was found in the DPPH test, indicating that the nanocomposite exhibited remarkable antioxidant characteristics. Subsequently, metronidazole was encapsulated with a success rate of 55.53 % at pH 1.2, while at pH 7.4 it gained 57.83 %. The drug release of nanocomposite at pH 1.2 after 330 min was 43.41 % and at pH 7.4 after 300 min it was 52.3 %. The results indicate its potential as an excellent candidate for drug delivery. Furthermore, pH was found to be an effective catalyst in the drug loading and release processes.

Eco-friendly green synthesis of silver nanoparticles from guajava leaves extract for controlling organophosphorus pesticides hazards, characterization, and in-vivo toxicity assessment

This study explores an eco-friendly approach to mitigate risks associated with organophosphorus insecticides, particularly Chlorpyrifos, by synthesizing silver nanoparticles (AgNPs) using Psidium guajava leaf extract and preparing a nanocomposite (AgNPs/S18) with Chlorpyrifos pesticide. The green-synthesized AgNPs and AgNPs/S18 nanocomposite were characterized using various analytical techniques, confirming the successful synthesis of AgNPs with an average size of 37 nm and forming a stable nanocomposite. Antibacterial assays demonstrated significant activity against Staphylococcus aureus, with AgNPs showing an 87.8% reduction and the nanocomposite achieving a 72% reduction in bacterial population. Cytotoxicity evaluations on normal liver and liver cancer cell lines revealed enhanced cytotoxicity of the nanocomposite compared to AgNPs alone, suggesting potential applications in targeted therapies. In vivo studies on rats revealed the protective effects of AgNPs and the nanocomposite against Chlorpyrifos-induced toxicity in liver and kidney tissues. Histopathological and ultrastructural analyses showed both treatments, particularly the nanocomposite, significantly mitigated cellular damage caused by Chlorpyrifos exposure. These findings suggest that green-synthesized AgNPs and their nanocomposite with Chlorpyrifos offer a promising approach to reducing pesticide hazards while maintaining efficacy. This research contributes to developing safer alternatives in pest management, addressing the need for more environmentally friendly agricultural practices while protecting human health and ecosystems.

Green Synthesis, Characterization and Pharmaceutical Applications of Biocompatible Zinc Oxide Nanoparticles Using Heliotropium rariflorum Stocks

Background: Zinc oxide nanoparticles are safe, non-toxic, and biocompatible. These NPs are used in food packaging materials, self-cleaning glass, ceramics, deodorants, sunscreens, paints, coatings, ointments, lotions, and as preservatives. This study explored the biological potential of ZnO nanoparticles synthesized using H. rariflorum. Methods: In vitro antibacterial and antifungal activities against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Candida albicans, Penicillium notatum, Aspergillus flavus, Aspergillus niger and Aspergillus solani were determined. Antioxidant activity was explored using the DPPH radical scavenging method. In vivo analgesic, antipyretic and sedative potential of synthesized nanoparticles was investigated using a mouse model. Results: SEM with various magnification powers showed that some particles were spherical while some were aggregated, flake-shaped, and hexagonal with rough and irregular surfaces. The EDX analysis revealed Zn (12.63%), O (22.83%) and C (63.11%) with trace quantities of Si (0.40%), Ca (0.54%) and P (0.49%). The XRD pattern indicated an amorphous state, with no peaks observed throughout the spectrum. The UV-visible spectrophotometry revealed a characteristic absorption peak at 375 nm, indicating the presence of ZnO nanoparticles. Fourier Transform Infrared Spectroscopy (FTIR) displayed several small peaks between 1793 and 2370 cm-1, providing evidence of the presence of different kinds of organic compounds with different functional groups. ZnO-NPs showed dose-dependent antibacterial and antifungal potential against all strains. Staphylococcus aureus and Candida albicans were the most susceptible strains. The nanoparticles exhibited a maximum antioxidant effect of 85.28% at 100 μg/mL. In this study, the acute toxicity test showed no mortality, and normal behavior was observed in mice at ZnO-NP doses of 5, 10, and 20 mg/kg. For analgesic and antipyretic activities, a two-way ANOVA revealed that dose, time, and the interaction between dose and time were significant. In contrast, the samples had a non-significant effect on sedative activity. Conclusions: This innovative study suggests a potential use of plant resources for managing microbes and treating various diseases, providing a scientific basis for the traditional use of H. rariflorum.

Antibacterial Properties of Copper Oxide Nanoparticles (Review)

The use of metal and metal oxide nanoparticles is frequently regarded as a potential solution to the issue of bacterial antibiotic resistance. Among the proposed range of nanoparticles with antibacterial properties, copper oxide nanoparticles are of particular interest. Although the antibacterial properties of copper have been known for a considerable period of time, studies on the effects of copper oxide nanomaterials with respect to biological systems have attracted considerable attention in recent years. This review presents a summary of the antibacterial properties of copper oxide nanoparticles, the mechanisms by which the antibacterial effect is realized, and the key reported methods of modifying these nanoparticles to improve their antibacterial activity. A comparative analysis of the effectiveness of these nanoparticles is presented depending on the type of microorganism, the shape of the nanoparticles, and the Gram classification of bacteria based on data from published sources. In addition, the review addresses the biological activities of copper oxide nanoparticles, including their antifungal and cytotoxic properties, as well as their "antioxidant" activity. According to the conducted analysis of the literature data, it can be concluded that copper oxide nanoparticles have a significant bacteriostatic potential with respect to a wide range of microorganisms and, in some cases, contribute to the inhibition of fungal growth. At the same time, the sensitivity of Gram-positive bacteria to the effect of copper oxide nanoparticles was often higher than that of Gram-negative bacteria.

Nanomaterials for Plant Disease Diagnosis and Treatment: A Review

Currently, the excessive use of pesticides has generated environmental pollution and harmful effects on human health. The controlled release of active ingredients through the use of nanomaterials (NMs) appears to reduce human exposure and ecosystem alteration. Although the use of NMs can offer an alternative to traditional methods of disease diagnosis and control, it is necessary to review the current approach to the application of these NMs. This review describes the most recent and significant advances in using NMs for diagnosing and treating plant diseases (bacteria, phytopathogenic fungi, viruses, and phytopathogenic nematodes) in cultivated plants. Most studies have focused on reducing, delaying, or eliminating bacteria, fungi, viruses, and nematodes in plants. Both metallic (including metal oxides) and organic nanoparticles (NPs) and composites are widely used in diagnosing and controlling plant diseases due to their biocompatibility and ease of synthesis. Few studies have been carried out with regard to carbon-based NPs due to their toxicity, so future studies should address the development of detection tools, ecological and economic impacts, and human health. The synergistic effect of NMs as fertilizers and pesticides opens new areas of knowledge on the mechanisms of action (plant-pathogen-NMs interaction), the interaction of NMs with nutrients, the effects on plant metabolism, and the traceability of NMs to implement sustainable approaches. More studies are needed involving in vivo models under international regulations to ensure their safety. There is still controversy in the release of NMs into the environment because they could threaten the stability and functioning of biological systems, so research in this area needs to be improved.

Interaction of plants and metal nanoparticles: Exploring its molecular mechanisms for sustainable agriculture and crop improvement

Metal nanoparticles offer promising prospects in agriculture, enhancing plant growth and ensuring food security. Silver, gold, copper, and zinc nanoparticles possess unique properties making them attractive for plant applications. Understanding molecular interactions between metal nanoparticles and plants is crucial for unlocking their potential to boost crop productivity and sustainability. This review explores metal nanoparticles in agriculture, emphasizing the need to understand these interactions. By elucidating mechanisms, it highlights the potential for enhancing crop productivity, stress tolerance, and nutrient-use efficiency, contributing to sustainable agriculture and food security. Quantifying benefits and risks reveal significant advantages. Metal nanoparticles enhance crop productivity by 20% on average and reduce disease incidence by up to 50% when used as antimicrobial agents. They also reduce nutrient leaching by 30% and enhance soil carbon sequestration by 15%, but concerns about toxicity, adverse effects on non-target organisms, and nanoparticle accumulation in the food chain must be addressed. Metal nanoparticles influence cellular processes including sensing, signaling, transcription, translation, and post-translational modifications. They act as signaling molecules, activate stress-responsive genes, enhance defense mechanisms, and improve nutrient uptake. The review explores their catalytic role in nutrient management, disease control, precision agriculture, nano-fertilizers, and nano-remediation. A bibliometric analysis offers insights into the current research landscape, highlighting trends, gaps, and future directions. In conclusion, metal nanoparticles hold potential for revolutionizing agriculture, enhancing productivity, mitigating environmental stressors, and promoting sustainability. Addressing risks and gaps is crucial for their safe integration into agricultural practices.

Aflatoxins in Peanut (Arachis hypogaea): Prevalence, Global Health Concern, and Management from an Innovative Nanotechnology Approach: A Mechanistic Repertoire and Future Direction

Arachis hypogaea is the most significant oilseed nutritious legume crop in agricultural trade across the world. It is recognized as a valued crop for its contributions to nourishing food, as a cooking oil, and for meeting the protein needs of people who are unable to afford animal protein. Currently, its production, marketability, and consumption are hindered because of Aspergillus species infection that consequently contaminates the kernels with aflatoxins. Regarding health concerns, humans and animals are affected by acute and chronic aflatoxin toxicity and millions of people are at high risk of chronic levels. Most methods used to store peanuts are traditional and serve effectively for short-term storage. Now the question for long-term storage has been raised, and this promptly finds potential approaches to the issue. It is imperative to reduce the aflatoxin levels in peanuts to a permissible level by introducing detoxifying innovations. Most of the detoxification reports mention physical, chemical, and biological techniques. However, many current approaches are impractical because of time consumption, loss of nutritional quality, or weak detoxifying efficiency. Therefore, it is crucial to investigate practical, economical, and green methods to control Aspergillus flavus that address current global food security problems. Herein, a green and economically revolutionary way is a nanotechnology that has demonstrated its potential to connect farmers to markets, elevate international marketability, improve human and animal health conditions, and enhance food quality and safety by the management of fungal diseases. Due to the antimicrobial potential of nanoparticles, they act as nanofungicides and have an incredible role in the control of aflatoxins. Nanoparticles have ultrasmall sizes and therefore penetrate the fungal body and invade the pathogen machinery, leading to fungal cell death by ROS production, mutation in DNA, disruption of organelles, and membrane leakage. This is the first mechanistic overview that unveils a comprehensive insight into aflatoxin contamination in peanuts, its prevalence, health effects, and management in addition to nanotechnological interventions that serve as a triple defense approach to detoxify aflatoxins. The optimum use of nanofungicides ensures food safety and the development of goals, especially "zero hunger".

Revolutionizing agriculture with nanotechnology: Innovative approaches in fungal disease management and plant health monitoring

Nanotechnology has emerged as a transformative force in modern agriculture, offering innovative solutions to address challenges related to fungal plant diseases and overall agricultural productivity. Specifically, the antifungal activities of metal, metal oxide, bio-nanoparticles, and polymer nanoparticles were examined, highlighting their unique mechanisms of action against fungal pathogens. Nanoparticles can be used as carriers for fungicides, offering advantages in controlled release, targeted delivery, and reduced environmental toxicity. Nano-pesticides and nano-fertilizers can enhance nutrient uptake, plant health, and disease resistance were explored. The development of nanosensors, especially those utilizing quantum dots and plasmonic nanoparticles, promises early and accurate detection of fungal pathogens, a crucial step in timely disease management. However, concerns about their potential toxic effects on non-target organisms, environmental impacts, and regulatory hurdles underscore the importance of rigorous research and impact assessments. The review concludes by emphasizing the significant prospects of nanotechnology in reshaping the future of agriculture but advocates for a balanced approach that prioritizes safety, sustainability, and environmental stewardship.

Nanoparticles as a Tool for Alleviating Plant Stress: Mechanisms, Implications, and Challenges

Plants, being sessile, are continuously exposed to varietal environmental stressors, which consequently induce various bio-physiological changes in plants that hinder their growth and development. Oxidative stress is one of the undesirable consequences in plants triggered due to imbalance in their antioxidant defense system. Biochemical studies suggest that nanoparticles are known to affect the antioxidant system, photosynthesis, and DNA expression in plants. In addition, they are known to boost the capacity of antioxidant systems, thereby contributing to the tolerance of plants to oxidative stress. This review study attempts to present the overview of the role of nanoparticles in plant growth and development, especially emphasizing their role as antioxidants. Furthermore, the review delves into the intricate connections between nanoparticles and plant signaling pathways, highlighting their influence on gene expression and stress-responsive mechanisms. Finally, the implications of nanoparticle-assisted antioxidant strategies in sustainable agriculture, considering their potential to enhance crop yield, stress tolerance, and overall plant resilience, are discussed.

Molecular characterization and evaluation of novel management options for Burkholderia glumae BG1, the causative agent of panicle blight of rice (Oryza sativa L.)

BACKGROUND

Bacterial panicle blight, incited by Burkholderia glumae, has impacted rice production globally. Despite its significance, knowledge about the disease and the virulence pattern of the causal agent is very limited. Bacterial panicle blight is a major challenge in the rice-growing belts of North-western India, resulting in yield reduction. However, the management of B. glumae has become a challenge due to the lack of proper management strategies.

METHODOLOGY AND RESULTS

Twenty-one BG strains have been characterized using the 16S rRNA and the gyrB gene-based sequence approach in the present study. The gyrB gene-based phylogenetic analysis resulted in geographic region-specific clustering of the BG isolates. The virulence screening of twenty-one BG strains by inoculating the pathogenic bacterial suspension of 1 × 10-8 cfu/ml at the booting stage (55 DAT) revealed the variation in the disease severity and the grain yield of rice plants. The most virulent BG1 strain resulted in the highest disease incidence (82.11%) and lowest grain yield (11.12 g/plant), and the least virulent BG10 strain resulted in lowest disease incidence of 18.94% and highest grain yield (24.62 g/plant). In vitro evaluation of various biocontrol agents and nano copper at different concentrations by agar well diffusion method revealed that nano copper at 1000 mg/L inhibited the colony growth of B. glumae. Under net house conditions, nano copper at 1000 mg/L reduced the disease severity to 21.23% and increased the grain yield by 20.91% (31.76 g per plant) compared to the positive control (COC 0.25% + streptomycin 200 ppm). Remarkably, pre-inoculation with nano copper at 1000 mg/L followed by challenge inoculation with B. glumae enhanced the activity of enzymatic antioxidants viz., Phenyl ammonia-lyase (PAL), Polyphenol oxidase (PPO) and Peroxidase (POX) and non-enzymatic antioxidant phenol. Additionally, we observed a substantial transcript level upregulation of six defense-related genes to several folds viz., OsPR2, OsPR5, OsWRKY71, OsPAL1, OsAPX1, and OsPPO1 in comparison to the pathogen control and healthy control.

CONCLUSIONS

Overall, our study provides valuable insights into the potential and practical application of nano copper for the mitigation of bacterial panicle blight, offering promising prospects for commercial utilization in disease management.

Antimicrobial Activity of Two Different Types of Silver Nanoparticles against Wide Range of Pathogenic Bacteria

The emergence of antibiotic-resistant bacteria, particularly the most hazardous pathogens, namely Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. (ESKAPE)-pathogens pose a significant threat to global health. Current antimicrobial therapies, including those targeting biofilms, have shown limited effectiveness against these superbugs. Nanoparticles, specifically silver nanoparticles (AgNPs), have emerged as a promising alternative for combating bacterial infections. In this study, two types of AgNPs with different physic-chemical properties were evaluated for their antimicrobial and antibiofilm activities against clinical ESKAPE strains. Two types of silver nanoparticles were assessed: spherical silver nanoparticles (AgNPs-1) and cubic-shaped silver nanoparticles (AgNPs-2). AgNPs-2, characterized by a cubic shape and higher surface-area-to-volume ratio, exhibited superior antimicrobial activity compared to spherical AgNPs-1. Both types of AgNPs demonstrated the ability to inhibit biofilm formation and disrupt established biofilms, leading to membrane damage and reduced viability of the bacteria. These findings highlight the potential of AgNPs as effective antibacterial agents against ESKAPE pathogens, emphasizing the importance of nanoparticle characteristics in determining their antimicrobial properties. Further research is warranted to explore the underlying mechanisms and optimize nanoparticle-based therapies for the management of infections caused by antibiotic-resistant bacteria.

Essential oil-grafted copper nanoparticles as a potential next-generation fungicide for holistic disease management in maize

Sustainable food production is necessary to meet the demand of the incessantly growing human population. Phytopathogens pose a major constraint in food production, and the use of conventional fungicides to manage them is under the purview of criticism due to their numerous setbacks. In the present study, essential oil-grafted copper nanoparticles (EGC) were generated, characterized, and evaluated against the maize fungal pathogens, viz., Bipolaris maydis, Rhizoctonia solani f. sp. sasakii, Macrophomina phaseolina, Fusarium verticillioides, and Sclerotium rolfsii. The ED₅₀ for the fungi under study ranged from 43 to 56 μg ml^-1, and a significant inhibition was observed at a low dose of 20 μg ml^-1 under in vitro conditions. Under net house conditions, seed treatment + foliar spray at 250 and 500 mg L^-1 of EGC performed remarkably against maydis leaf blight (MLB), with reduced percent disease index (PDI) by 27.116 and 25.292%, respectively, in two Kharif seasons (May-Sep, 2021, 2022). The activity of enzymatic antioxidants, viz., β-1, 3-glucanase, PAL, POX, and PPO, and a non-enzymatic antioxidant (total phenolics) was increased in treated maize plants, indicating host defense was triggered. The optimum concentrations of EGC (250 mg L^-1 and 500 mg L^-1) exhibited improved physiological characteristics such as photosynthetic activity, shoot biomass, plant height, germination percentage, vigor index, and root system traits. However, higher concentrations of 1,000 mg L^-1 rendered phytotoxicity, reducing growth, biomass, and copper bioaccumulation to high toxic levels, mainly in the foliar-sprayed maize leaves. In addition, EGC and copper nanoparticles (CuNPs) at 1,000 mg L^-1 reduced the absorption and concentration of manganese and zinc indicating a negative correlation between Cu and Mn/Zn. Our study proposes that the CuNPs combined with EO (Clove oil) exhibit astounding synergistic efficacy against maize fungal pathogens and optimized concentrations can be used as an alternative to commercial fungicides without any serious impact on environmental health.

Double- or Triple-Tiered Protection: Prospects for the Sustainable Application of Copper-Based Antimicrobial Compounds for Another Fourteen Decades

Copper (Cu)-based antimicrobial compounds (CBACs) have been widely used to control phytopathogens for nearly fourteen decades. Since the first commercialized Bordeaux mixture was introduced, CBACs have been gradually developed from highly to slightly soluble reagents and from inorganic to synthetic organic, with nanomaterials being a recent development. Traditionally, slightly soluble CBACs form a physical film on the surface of plant tissues, separating the micro-organisms from the host, then release divalent or monovalent copper ions (Cu²⁺ or Cu⁺) to construct a secondary layer of protection which inhibits the growth of pathogens. Recent progress has demonstrated that the release of a low concentration of Cu²⁺ may elicit immune responses in plants. This supports a triple-tiered protection role of CBACs: break contact, inhibit microorganisms, and stimulate host immunity. This spatial defense system, which is integrated both inside and outside the plant cell, provides long-lasting and broad-spectrum protection, even against emergent copper-resistant strains. Here, we review recent findings and highlight the perspectives underlying mitigation strategies for the sustainable utilization of CBACs.

Engineered Metal Oxide Nanoparticles as Fungicides for Plant Disease Control

Metal oxide nanoparticles are considered to be good alternatives as fungicides for plant disease control. To date, numerous metal oxide nanoparticles have been produced and evaluated as promising antifungal agents. Consequently, a detailed and critical review on the use of mono-, bi-, and tri-metal oxide nanoparticles for controlling phytopathogenic fungi is presented. Among the studied metal oxide nanoparticles, mono-metal oxide nanoparticles-particularly ZnO nanoparticles, followed by CuO nanoparticles -are the most investigated for controlling phytopathogenic fungi. Limited studies have investigated the use of bi- and tri-metal oxide nanoparticles for controlling phytopathogenic fungi. Therefore, more studies on these nanoparticles are required. Most of the evaluations have been carried out under in vitro conditions. Thus, it is necessary to develop more detailed studies under in vivo conditions. Interestingly, biological synthesis of nanoparticles has been established as a good alternative to produce metal oxide nanoparticles for controlling phytopathogenic fungi. Although there have been great advances in the use of metal oxide nanoparticles as novel antifungal agents for sustainable agriculture, there are still areas that require further improvement.

Nanofungicides with Selenium and Silicon Can Boost the Growth and Yield of Common Bean (Phaseolus vulgaris L.) and Control Alternaria Leaf Spot Disease

There is an urgent need to reduce the intensive use of chemical fungicides due to their potential damage to human health and the environment. The current study investigated whether nano-selenium (nano-Se) and nano-silica (nano-SiO2) could be used against the leaf spot disease caused by Alternaria alternata in a common bean (Phaseolus vulgaris L.). The engineered Se and SiO2 nanoparticles were compared to a traditional fungicide and a negative control with no treatment, and experiments were repeated during two successive seasons in fields and in vitro. The in vitro study showed that 100 ppm nano-Se had an efficacy rate of 85.1% on A. alternata mycelial growth, followed by the combined applications (Se + SiO2 at half doses) with an efficacy rate of 77.8%. The field study showed that nano-Se and the combined application of nano-Se and nano-SiO2 significantly decreased the disease severity of A. alternata. There were no significant differences among nano-Se, the combined application, and the fungicide treatment (positive control). As compared to the negative control (no treatment), leaf weight increased by 38.3%, the number of leaves per plant by 25.7%, chlorophyll A by 24%, chlorophyll B by 17.5%, and total dry seed yield by 30%. In addition, nano-Se significantly increased the enzymatic capacity (i.e., CAT, POX, PPO) and antioxidant activity in the leaves. Our current study is the first to report that the selected nano-minerals are real alternatives to chemical fungicides for controlling A. alternata in common beans. This work suggests the potential of nanoparticles as alternatives to fungicides. Further studies are needed to better understand the mechanisms and how different nano-materials could be used against phytopathogens.

Biosynthesis of Novel Tellurium Nanorods by Gayadomonas sp. TNPM15 Isolated from Mangrove Sediments and Assessment of Their Impact on Spore Germination and Ultrastructure of Phytopathogenic Fungi

The biosynthesis of nanoparticles using green technology is emerging as a cost-efficient, eco-friendly and risk-free strategy in nanotechnology. Recently, tellurium nanoparticles (TeNPs) have attracted growing attention due to their unique properties in biomedicine, electronics, and other industrial applications. The current investigation addresses the green synthesis of TeNPs using a newly isolated mangrove-associated bacterium, Gayadomonas sp. TNPM15, and their impact on the phytopathogenic fungi Fusarium oxysporum and Alternaria alternata. The biogenic TeNPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared (FTIR). The results of TEM revealed the intracellular biosynthesis of rod-shaped nanostructures with a diameter range from 15 to 23 nm and different lengths reaching up to 243 nm. Furthermore, the successful formation of tellurium nanorods was verified by SEM-EDX, and the XRD pattern revealed their crystallinity. In addition, the FTIR spectrum provided evidence for the presence of proteinaceous capping agents. The bioinspired TeNPs exhibited obvious inhibitory effect on the spores of both investigated phytopathogens accomplished with prominent ultrastructure alternations, as evidenced by TEM observations. The biogenic TeNPs impeded spore germination of F. oxysporum and A. alternata completely at 48.1 and 27.6 µg/mL, respectively. Furthermore, an increase in DNA and protein leakage was observed upon exposure of fungal spores to the biogenic TeNPs, indicating the disruption of membrane permeability and integrity. Besides their potent influence on fungal spores, the biogenic TeNPs demonstrated remarkable inhibitory effects on the production of various plant cell wall-degrading enzymes. Moreover, the cytotoxicity investigations revealed the biocompatibility of the as-prepared biogenic TeNPs and their low toxicity against the human skin fibroblast (HSF) cell line. The biogenic TeNPs showed no significant cytotoxic effect towards HSF cells at concentrations up to 80 μg/mL, with a half-maximal inhibitory concentration (IC50) value of 125 μg/mL. The present work spotlights the antifungal potential of the biogenic TeNPs produced by marine bacterium against phytopathogenic fungi as a promising candidate to combat fungal infections.