Engineered chitosan based nanomaterials: Bioactivities, mechanisms and perspectives in plant protection and growth

Review of current trends in chitosan based controlled and slow-release fertilizer: From green chemistry to circular economy

The demand for food is increasing rapidly with the growth of the global population. To ensure global food security, fertilizers are essential. Controlled-release fertilizers (CRFs) are a highly effective type of fertilizer that have been developed to meet this need. While CRFs offer significant advantages over traditional fertilizers, their use has been limited due to high production costs and negative impact on the environment. CRFs are manufactured and applied without considering the resource-use efficiency of the production process or the potential ecological consequences of fertilizer application. To tackle these issues, biopolymer-based CRFs have been developed. These innovative fertilizers are created by coating granules with biodegradable and eco-friendly biopolymers (chitosan, starch and cellulose). In addition, these groundbreaking fertilizers align with the tenets of the circular economy, which involve formulating products that enable a gradual and steady dispensation of nutrients over an extended period. Our objective in embracing these fertilizers is to transcend the traditional linear "take, make, dispose" approach and transition towards a more sustainable and circular model. This approach not only enhances nutrient delivery efficiency but also contributes significantly to reducing the environmental impact associated with conventional fertilizer use. Afterward, the research explored various aspects of controlled-release fertilizers (CRFs), including the mechanisms of nutrient release, the types of coating materials used, and the techniques employed for coating. The study also examined the benefits and challenges associated with CRFs and analyzed how specific parameters influence the nutrient release mechanisms.

Synthesis and characterization of novel histidine functionalized chitosan nanoformulations and its bioactivity in tomato plant

The use of novel active ingredients for the functional modification of chitosan nanoformulations has attracted global attention. In this study, chitosan has been functionalized via histidine to craft novel chitosan-histidine nanoformulation (C-H NF) using ionic gelation method. C-H NF exhibited elite physico-biochemical properties, influencing physiological and biochemical dynamics in Tomato. These elite properties include homogenous-sized nanoparticles (314.4 nm), lower PDI (0.218), viscosity (1.43 Cps), higher zeta potential (11.2 mV), nanoparticle concentration/ml (3.53 × 108), conductivity (0.046 mS/cm), encapsulation efficiency (53%), loading capacity (24%) and yield (32.17%). FTIR spectroscopy revealed histidine interaction with C-H NF, while SEM and TEM exposed its porous structure. Application of C-H NF to Tomato seedling and potted plants through seed treatment and foliar spray positively impacts growth parameters, antioxidant-defense enzyme activities, reactive oxygen species (ROS) content, and chlorophyll and nitrogen content. We claim that the histidine-functionalized chitosan nanoformulation enhances physico-biochemical properties, highlighting its potential to elevate biochemical and physiological processes of Tomato plant.

Chitosan-Coated Fosetyl-Al Nanocrystals' Efficacy on Nicotiana tabacum Colonized by Xylella fastidiosa

Xylella fastidiosa (Xf) is a quarantine plant pathogen capable of colonizing the xylem of a wide range of hosts. Currently, there is no cure able to eliminate the pathogen from a diseased plant, but several integrated strategies have been implemented for containing the spread of Xf. Nanotechnology represents an innovative strategy based on the possibility of maximizing the potential antibacterial activity by increasing the surface-to-volume ratio of nanoscale formulations. Nanoparticles based on chitosan and/or fosetyl-Al have shown different in vitro antibacterial efficacy against Xf subsp. fastidiosa (Xff) and pauca (Xfp). This work demonstrated the uptake of chitosan-coated fosetyl-Al nanocrystals (CH-nanoFos) by roots and their localization in the stems and leaves of Olea europaea plants. Additionally, the antibacterial activity of fosetyl-Al, nano-fosetyl, nano-chitosan, and CH-nanoFos was tested on Nicotiana tabacum cultivar SR1 (Petite Havana) inoculated with Xff, Xfp, or Xf subsp. multiplex (Xfm). The bacterial load was evaluated with qPCR, and the results showed that CH-nanoFos was the only treatment able to reduce the colonization of Xff, Xfm, and Xfp in tobacco plants. Additionally, the area under the disease progress curve, used to assess symptom development in tobacco plants inoculated with Xff, Xfm, and Xfp and treated with CH-nanoFos, showed a reduction in symptom development. Furthermore, the twitching assay and bacterial growth under microfluidic conditions confirmed the antibacterial activity of CH-nanoFos.

Xylooligosaccharides Enhance Lettuce Root Morphogenesis and Growth Dynamics

Enhancing root development is pivotal for boosting crop yield and augmenting stress resilience. In this study, we explored the regulatory effects of xylooligosaccharides (XOSs) on lettuce root growth, comparing their impact with that of indole-3-butyric acid potassium salt (IBAP). Treatment with XOS led to a substantial increase in root dry weight (30.77%), total root length (29.40%), volume (21.58%), and surface area (25.44%) compared to the water-treated control. These enhancements were on par with those induced by IBAP. Comprehensive phytohormone profiling disclosed marked increases in indole-3-acetic acid (IAA), zeatin riboside (ZR), methyl jasmonate (JA-ME), and brassinosteroids (BRs) following XOS application. Through RNA sequencing, we identified 3807 differentially expressed genes (DEGs) in the roots of XOS-treated plants, which were significantly enriched in pathways associated with manganese ion homeostasis, microtubule motor activity, and carbohydrate metabolism. Intriguingly, approximately 62.7% of the DEGs responsive to XOS also responded to IBAP, underscoring common regulatory mechanisms. However, XOS uniquely influenced genes related to cutin, suberine, and wax biosynthesis, as well as plant hormone signal transduction, hinting at novel mechanisms of stress tolerance. Prominent up-regulation of genes encoding beta-glucosidase and beta-fructofuranosidase highlights enhanced carbohydrate metabolism as a key driver of XOS-induced root enhancement. Collectively, these results position XOS as a promising, sustainable option for agricultural biostimulation.

Development, characterization, and evaluation of Zn-SA-chitosan bionanoconjugates on wheat seed, experiencing chilling stress during germination

This study aimed to develop and characterize the chitosan bionanoconjugates (BNCs) loaded with zinc (Zn) and salicylic acid (SA) and test their efficacy on wheat seed exposed to chilling stress. BNCs developed were spherical (480 ± 6.0 nm), porous, and positively charged (+25.2 ± 2.4 mV) with regulated nutrient release properties. They possessed complexation efficiency of 78.4 and 58.9 % for Zn, and SA respectively. BET analysis further confirmed a surface area of 12.04 m2/g. Release kinetics substantiated the release rates of Zn and SA, as 0.579 and 0.559 % per hour, along with a half-life of 119.7 and 124.0 h, respectively. BNCs positively affected the germination potential of wheat seeds under chilling stress as observed by significantly (p < 0.05) reduced mean emergence time (18 %), and increased germination rate (22 %), compared to the control. Higher activities of reserve mobilizing enzymes (α-amylase- 6.5 folds, protease -10.2 folds) as well as faster reserve mobilization of starch (64.4 %) and protein (63.5 %) molecules were also observed. The application further led to increased levels of the antioxidant enzymes (SOD and CAT) and reduced oxidative damage (MDA and H2O2). Thus, it is inferred that the developed BNCs could help substantially improve the germination and reserve mobilization potential, thereby increasing the crop yield.

Chitosan derivatives act as a bio-stimulants in plants: A review

Chitosan has been considered an eco-friendly biopolymer. Chitosan is a natural polycationic linear polysaccharide composed of D-glucosamine and N-acetyl-D-glucosamine linked by β-1,4-glycosidic bonds. Chitosan has been used as an eco-friendly biopolymer for so many agricultural applications. Unfortunately, the relatively poor solubility and poor antimicrobial properties limit its widespread applications in agriculture sciences. Hence, chitosan derivatives are produced via various chemical approaches such as cross-linking, carboxylation, ionic binding, and so on. As an alternative to chemical fertilizers, chitosan derivatives, chitosan conjugates, nanostructures, semisynthetic derivatives, oligo mixes, chitosan nanoparticles, and chitosan nano-carriers are synthesized for various agricultural applications. Its several chemical and physical properties such as biocompatibility, biodegradability, permeability, cost-effectiveness, low toxicity, and environmental friendliness make it useful for many agricultural applications. Hence, popularizing its use as an elicitor molecule for different host-pathogen interaction studies. Thus, the versatile and plethora of chitosan derivatives are gaining momentum in agricultural sciences. Bio-stimulant properties and multifunctional benefits are associated with further prospective research. Therefore, in the present review, we decipher the potential pros and cons of chitosan derivatives in plants.

The efficacy of chemical inducers and fungicides in controlling tomato root rot disease caused by Rhizoctoniasolani

Chitosan is an environmentally friendly natural substance that is used in crop disease management as an alternative to chemical pesticides. A significant issue restricting output in Egypt is root rot, which is a disease, caused by Rhizoctonia solani. Therefore, a greenhouse experiment was conducted to assess the effects of R. solani on 60-day-old tomato plants under fungal infection and to determine the antifungal activity of chitosan and Rizolax T fungicide against the pathogenic fungus. The findings demonstrated that 4 g/L of chitosan seed application completely obstructed the radial mycelial growth of R. solani and decreased the disease severity. Pathogenic infection significantly decreased morphological characteristics and total chlorophyll but significantly increased carotenoid, total thiol, non-protein thiol, protein thiol, antioxidant enzymes, oxidative stress, total phenolic, total flavonoid, and isoflavone compared to healthy plants. Tomato plants treated with chitosan exhibited lower rates of oxidative stress, but higher levels of all previously mentioned parameters compared to untreated infected plants. The number and molecular mass of protein banding patterns varied in all treated tomato plants as compared to the healthy control. There are 42 bands in the treatments, and their polymorphism rate is 69.55%. Moreover, the number and density of α- and β-esterase, and peroxidase isozymes in treated tomato plants exhibited varied responses. Moreover, in treated and control plants, chitosan treatment raised the expression levels of phenylalanine ammonia-lyase, pathogenesis-related protein-1, β-1,3-glucanases and chitinase. In conclusions, chitosan reduces R. solani infection by controlling the biochemical and molecular mechanisms in tomato plants during infection.

Chitosan- and gallic acid-based (NPF) displayed antibacterial activity against three Pseudomonas spp. plant pathogens and boosted systemic acquired resistance in kiwifruit and olive plants

BACKGROUD

Pseudomonas syringae pv. actinidiae (Psa), P. syringae pv. tomato (Pst) and P. savastanoi pv. savastanoi (Psav) are bacterial plant pathogens with worldwide impact that are mainly managed by the preventive application of cupric salts. These are dangerous for ecosystems and have favoured the selection of resistant strains, so they are candidates to be replaced in the next few years. Thus, there is an urgent need to find efficient and bio-based solutions to mitigate these bacterial plant diseases. Nanotechnology could represent an innovative way to control plant diseases, providing alternative solutions to the agrochemicals traditionally employed, thanks to the formulation of the so-called third-generation and nanotechnology-based agrochemicals.

RESULTS

In this work, a novel nanostructured formulation (NPF) composed of cellulose nanocrystals (CNC) as carrier, high amylose starch (HAS) as excipient, and chitosan (CH) and gallic acid (GA) as antimicrobials, was tested at 2% in vitro and in vivo with respect to the three different Pseudomonas plant pathogens. In vitro agar assays demonstrated that the NPF inhibited ≤80% Psa, Pst and Psav. Moreover, the NPF did not decrease biofilm synthesis and it did not influence bacterial cells flocculation and adhesion. On plants, the NPF displayed complete biocompatibility and boosted the transcript levels of the major systemic acquired resistance responsive genes in kiwifruit and olive plants.

CONCLUSION

This works provides novel and valuable information regarding the several modes-of-action of the novel NPF, which could potentially be useful to mitigate Psa, Pst and Psav infections even in organic agriculture. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Phytotoxic fungal secondary metabolites as herbicides

Among the alternatives to synthetic plant protection products, biocontrol appears as a promising method. This review reports on the diversity of fungal secondary metabolites phytotoxic to weeds and on the approach generally used to extract, characterize, identify and exploit them for weed management. The 183 phytotoxic fungal secondary metabolites discussed in this review fall into five main classes of molecules: 61 polyketides, 53 terpenoids, 36 nitrogenous metabolites, 18 phenols and phenolic acids, and 15 miscellaneous. They are mainly produced by the genera Drechslera, Fusarium and Alternaria. The phytotoxic effects, more often described by the symptoms they produce on plants than by their mode of action, range from inhibition of germination to inhibition of root and vegetative growth, including tissue and organ alterations. The biochemical characterization of fungal secondary metabolites requires expertise and tools to carry out fungal cultivation and metabolite extraction, phytotoxicity tests, purification and fractionation of the extracts, and chemical identification procedures. Phytotoxicity tests are mainly carried out under controlled laboratory conditions (not always on whole plants), while effectiveness against targeted weeds and environmental impacts must be assessed in greenhouses and open fields. These steps are necessary for the formulation of effective, environment-friendly fungal secondary metabolites-derived bioherbicides using new technologies such as nanomaterials. © 2023 Society of Chemical Industry.

Green synthesis of a chlorfenapyr chitosan nanopesticide for maize root application: Reducing environmental pollution and risks to nontarget organisms

Chlorfenapyr (CHL) is a pyrrole insecticide with a novel structure that is used to control resistant pests. However, its weak systemic activity limits its application to crop roots. Herein, a novel CHL formulation with improved effective utilization rates and suitability for root application is developed to avoid or reduce contamination caused by pesticide spraying. Accordingly, we prepared CHL@CS/CMCS nanoparticle (NP) suspensions with a particle size of approximately 100 nm using chitosan (CS) and carboxymethyl chitosan (CMCS). These suspensions exhibited better thermal stability, adhesion, permeability and systemic activity than a CHL suspension concentrate (CHL-SC). The nanoformulation deposition rate on maize leaves after spraying was 12.28 mg/kg, significantly higher than that of CHL-SC. The nanosuspension was effectively absorbed and transported by roots after irrigation and was suitable for root application. The efficacy was 89.46-92.36 % against Spodoptera frugiperda at 7 d, 7.5-17.5 times higher than that of CHL-SC. Furthermore, the CHL@CS/CMCS nanosuspension was safer for earthworms. These results suggest that chitosan-based nanoformulations improve the efficacy, utilization efficiency and active period of CHL control, providing a new approach for CHL application, reducing pollutant dispersal and the environmental impacts of pesticide application and facilitating sustainable agricultural production.

Chitosan nanoparticles and based composites as a biocompatible vehicle for drug delivery: A review

The shellfish processing industry is one of the largest growing industries across the globe with a market size of around USD 62B. However, it also leads to a significant environmental issue as it produces >80,000 tons of waste shells globally. Unfortunately, the slow degradation of this waste causes it to accumulate over time, posing a serious threat to the marine environment. The key solution to this problem is to recycle this sea waste into a valuable product like chitin which is further used to produce chitosan. Chitosan is a natural biopolymeric substance obtained via N-deacetylation of the chitin. The chitosan-based nanoparticles are further useful for the fabrication of biopolymeric nanocomposites which are used in various biomedical applications specifically in drug delivery. Here, we review the recent advancements in the development of chitosan-based nanocomposites as a biocompatible carrier for drug delivery, specifically focusing on gene delivery, wound healing, microbial treatment, and anticancer drug delivery. By providing a valuable and up-to-date resource, this review illuminates the current state of research concerning chitosan's pivotal role in the biomedical domain as an efficacious drug delivery agent.

Nanofertilizers: The Next Generation of Agrochemicals for Long-Term Impact on Sustainability in Farming Systems

The microflora of the soil is adversely affected by chemical fertilizers. Excessive use of chemical fertilizers has increased crop yield dramatically at the cost of soil vigor. The pH of the soil is temporarily changed by chemical fertilizers, which kill the beneficial soil microflora and can cause absorption stress on crop plants. This leads to higher dosages during the application, causing groundwater leaching and environmental toxicity. Nanofertilizers (NFs) reduce the quantity of fertilizer needed in agriculture, enhance nutrient uptake efficiency, and decrease fertilizer loss due to runoff and leaching. Moreover, NFs can be used for soil or foliar applications and have shown promising results in a variety of plant species. The main constituents of nanomaterials are micro- and macronutrient precursors and their properties at the nanoscale. Innovative approaches to their application as a growth promoter for crops, their modes of application, and the mechanism of absorption in plant tissues are reviewed in this article. In addition, the review analyzes potential shortcomings and future considerations for the commercial agricultural application of NFs.

Chitosan fabricated biogenic silver nanoparticles (Ch@BSNP) protectively modulate the defense mechanism of tomato during bacterial leaf spot (BLS) disease

Herein, the impact of chitosan fabricated biogenic silver nanoparticles (Ch@BSNP) has been evaluated for the protective management of bacterial leaf spot (BLS) disease in tomatoes caused by Xanthomonas campestris (NCIM5028). The Ch@BSNP originated by the Trichoderma viride (MTCC5661) derived extracellular compounds and subsequent chitosan hybridization. Spherical-shaped Ch@BSNP (30-35 nm) treated diseased plants were able to combat the biotic stress, as evidenced by the decreased elevated response of stress markers viz; anthocyanin (34.02%), proline (45.00%), flavonoids (20.26%), lipid peroxidation (10.00%), guaiacol peroxidase (36.58%), ascorbate peroxidase (41.50%), polyphenol oxidase (25.34%) and phenylalanine ammonia-lyase (2.10 fold) as compared to untreated diseased plants. Increased biochemical content specifically sugar (15.43%), phenolics (49.10%), chlorophyll, and carotenoids were measured in Ch@BSNP-treated diseased plants compared to untreated X. campestris-infested plants. The Ch@BSNP considerably reduced stress by increasing net photosynthetic rate and water use efficiency along with decreased transpiration rate and stomatal conductance in comparison to infected plants. Additionally, the expression of defense-regulatory genes viz; growth responsive (AUX, GH3, SAUR), early defense responsive (WRKYTF22, WRKY33, NOS1), defense responsive (PR1, NHO1, NPR1), hypersensitivity responsive (Pti, RbohD, OXI1) and stress hormones responsive (MYC2, JAR1, ERF1) were found to be upregulated in diseased plants while being significantly downregulated in Ch@BSNP-treated diseased plants. Furthermore, fruits obtained from pathogen-compromised plants treated with Ch@BSNP had higher levels of health-promoting compounds including lycopene and beta-carotene than infected plant fruits. This nano-enabled and environmentally safer crop protection strategy may encourage a sustainable agri-system towards the world's growing food demand and promote food security.

Chitosan nanocomposite as an effective carrier of potential herbicidal metabolites for noteworthy phytotoxic effect against major aquatic invasive weed water hyacinth (Eichhornia crassipes)

In this current work, the herbicidal activity of fungal metabolites stacked chitosan nanocomposite against significant aquatic invasive weed Eichhornia crassipes (water hyacinth) was examined. Herbicidal metabolites from the fungal strain Allophoma oligotrophica were extracted and purified under standard condition. Altered ionic gelation technique was received for the amalgamation of chitosan nanocomposite fabricated with herbicidal metabolites. Synthesized nanocomposite incited checked herbicidal impact on the leaflets of water hyacinth. Synthesized nanocomposite induced marked herbicidal effect on the tested leaflets of water hyacinth. Necrotic development on the tested leaflets at earlier incubation period followed by progressive enhancement of necrotic lesion reveals the noteworthy herbicidal activity of the synthesized nanocomposite. Parenchymal, mesenchymal tissue disintegration, reduction of total chlorophyll content, elevated anti oxidative enzymes and changes in qualitative protein profiling of tested leaflets reveals the nanocomposite induced noteworthy morphometric and functional effects. Effect of solvents on the release profile demonstrates that ethyl acetate treatment brought about controlled or sustained release of metabolites. No sign of toxic effect on the zebra fish embryonic developmental stages revealed biocompatibility of the nanocomposite.

Nanoencapsulation Boosts the Copper-Induced Defense Responses of a Susceptible Coffea arabica Cultivar against Hemileia vastatrix

Due to the environmental risks of conventional Cu-based fungicides, Cu-loaded chitosan nanoparticles have been developed as nano-pesticides, aiming to protect plants against different diseases. In this sense, the objective was to verify the effects of chitosan nanoparticles containing Cu2+ ions on leaf discs of Coffea arabica cv. IPR 100 infected with Hemileia vastatrix. The treatments were water as a control (CONT), unloaded chitosan nanoparticles (NP), chitosan nanoparticles containing Cu2+ ions (NPCu), and free Cu2+ ions (Cu). Different concentrations of NP (0.25; 0.5; 1 g L-1) and Cu2+ ions (1.25; 2.5; 5 mmol L-1) were tested. The severity of the coffee rust was 42% in the CONT treatment, 22% in NP, and 2% in NPCu and Cu. The treatments protected coffee leaves; however, NPCu stood out for initial stress reduction, decreasing Cu phytotoxicity, promoting photosynthetic activity maintenance, and increasing antioxidant responses, conferring significant protection against coffee rust. At low concentrations (1.25 mmol L-1), NPCu showed higher bioactivity than Cu. These results suggest that Cu-loaded chitosan nanoparticles can induce a more significant plant defense response to the infection of Hemileia vastatrix than conventional Cu, avoiding the toxic effects of high Cu concentrations. Thus, this nanomaterial has great potential to be used as nano-pesticides for disease management.

Meta-analysis of chitosan-mediated effects on plant defense against oxidative stress

Chitosan, as a natural non-toxic biomaterial, has been demonstrated to enhance plant defense against oxidative stress. However, the general pattern and mechanism of how chitosan application modifies the amelioration of oxidative stress in plants have not been elucidated yet. Herein, we performed a meta-analysis of 58 published articles up to January 2022 to fill this knowledge gap, and found that chitosan application significantly increased the antioxidant enzyme activity (by 40.6 %), antioxidant metabolites content (by 24.6 %), defense enzyme activity (by 77.9 %), defense-related genes expression (by 103.2 %), phytohormones (by 26.9 %), and osmotic regulators (by 23.2 %) under stress conditions, which in turn notably reduced oxidative stress (by 32.2 %), and increased plant biomass (by 28.1 %) and yield (by 15.7 %). Moreover, chitosan-mediated effects on the amelioration of oxidative stress depended on the properties and application methods of chitosan. Our findings provide a comprehensive understanding of the mechanism of chitosan-alleviated oxidative stress, which would promote the application of chitosan in plant protection in agriculture.

Soil Treatment with Nitric Oxide-Releasing Chitosan Nanoparticles Protects the Root System and Promotes the Growth of Soybean Plants under Copper Stress

The nanoencapsulation of nitric oxide (NO) donors is an attractive technique to protect these molecules from rapid degradation, expanding, and enabling their use in agriculture. Here, we evaluated the effect of the soil application of chitosan nanoparticles containing S-nitroso-MSA (a S-nitrosothiol) on the protection of soybeans (Glycine max cv. BRS 257) against copper (Cu) stress. Soybeans were grown in a greenhouse in soil supplemented with 164 and 244 mg kg-1 Cu and treated with a free or nanoencapsulated NO donor at 1 mM, as well as with nanoparticles without NO. There were also soybean plants treated with distilled water and maintained in soil without Cu addition (control), and with Cu addition (water). The exogenous application of the nanoencapsulated and free S-nitroso-MSA improved the growth and promoted the maintenance of the photosynthetic activity in Cu-stressed plants. However, only the nanoencapsulated S-nitroso-MSA increased the bioavailability of NO in the roots, providing a more significant induction of the antioxidant activity, the attenuation of oxidative damage, and a greater capacity to mitigate the root nutritional imbalance triggered by Cu stress. The results suggest that the nanoencapsulation of the NO donors enables a more efficient delivery of NO for the protection of soybean plants under Cu stress.

A review of nanoparticle synthesis and application in the suppression of diseases in fruits and vegetables

Fruits and vegetables are an integral part of our diet attributed to their appealing taste, flavor, and health-promoting characteristics. However, due to their high-water activity, they are susceptible to microbial spoilage and diseases at any step in the food supply chain, from pre-harvest treatment to post-harvest storage and transportation. As a result, food researchers and engineers are developing innovative technologies that can be used to reduce the loss of fruits and vegetables on-farm and during postharvest processing. The purpose of this study was to gather and discuss the scientific data on the disease-suppressive activity of nanoparticles against plant pathogens. The progress and limitations of innovative approaches for improving nanoparticles' efficiency and dependability have been studied to develop effective substitutes for synthetic chemical fungicides and pesticides, in managing disease in fruits and vegetables. The findings of this study strongly suggests that nanotechnology has the required ability for disease suppression in fruits and vegetables. Applications of specific nanoparticles under specified conditions can enhance nutrition delivery to plants, provide better antibacterial and disease suppression activity. Nanoparticles can also lessen the quantity of agrichemicals/metals released into the environment as compared to standard formulations, which is one of the most impressive advances.

Interactive Effect of Biological Agents Chitosan, Lentinan and Ningnanmycin on Papaya Ringspot Virus Resistance in Papaya (Carica papaya L.)

The papaya industry is mainly impacted by viral diseases, especially papaya ringspot disease (PRSD) caused by papaya ringspot virus (PRSV). So far, research on the interaction between Chitosan, Lentinan and Ningnanmycin on PRSD has not been reported. This research studied the controlled and interactive effect of three biological agents, namely, Chitosan (C), Lentinan (L) and Ningnanmycin (N), on PRSV in papaya, individually and collectively. The changes in disease index, controlled effect, Peroxidase (POD), Polyphenol oxidase (PPO), Superoxide dismutase (SOD), growth and development of plants were observed at the seedling stage, in pots, and at the fruiting stage, in the field. The appearance and nutrient contents of fruits were measured during the fruit stage. The disease index of PRSV, at seedling and fruiting stages, was significantly lower for chitosan, lentinan and ningnanmycin and their interactive effect, compared to a control check treatment. The activity of the defense enzymes could be improved by the three kinds of biological agents and their interactive effect, especially lentinan and ningnanmycin. The chlorophyll content, plant height, stem diameter and fruit quality rose significantly under chitosan, lentinan and ningnanmycin treatments. The interaction of LN could inhibit PRSV disease at the seedling and fruiting stages of papaya, and promote the growth of plants and the quality of fruit at the fruit stage. Hence, this study provides the theoretical foundation for the biological control of papaya ringspot disease.

β-Glucan and its nanocomposites in sustainable agriculture and environment: an overview of mechanisms and applications

β-Glucan is an eco-friendly, biodegradable, and economical biopolymer with important roles for acquiring adaptations to mitigate climate change in crop plants. β-Glucan plays a crucial role in the activation of functional plant innate immune system by triggering the downward signaling cascade/s, resulting in the accumulation of different pathogenesis-related proteins (PR-proteins), reactive oxygen species (ROS), antioxidant defense enzymes, Ca2+-influx as well as activation of mitogen-activated protein kinase (MAPK) pathway. Recent experimental studies have shown that β-glucan recognition is mediated by co-receptor LysMPRR (lysin motif pattern recognition receptor)-CERK1 (chitin elicitor receptor kinase 1), LYK4, and LYK5 (LysM-containing receptor-like kinase), as well as different receptor systems in plants that could be plant species-specific and/or age and/or tissue-dependent. Transgenic overexpression of β-glucanase, chitinase, and/or in combination with other PR-proteins like cationic peroxidase, AP24,thaumatin-likeprotein 1 (TLP-1) has also been achieved for improving plant disease resistance in crop plants, but the transgenic methods have some ethical and environmental concerns. In this regard, elicitation of plant immunity using biopolymer like β-glucan and chitosan offers an economical, safe, and publicly acceptable method. The β-glucan and chitosan nanocomposites have proven to be useful for the activation of plant defense pathways and to enhance plant response/systemic acquired resistance (SAR) against broad types of plant pathogens and mitigating multiple stresses under the changing climate conditions.

Evaluating extremophilic microorganisms in industrial regions

Abiotic and biotic stresses have a major impact on crop growth. Stress affects the root system and decreases the amount of nutrients in fruits. Modern agricultural technologies help replace mineral fertilizers with new generation biopreparation. Unlike chemical fertilizers, biofertilizers reduce the risk of adverse environmental impacts. Of special interest are extremophilic microorganisms able to survive in extreme conditions. We aimed to study the phytostimulating ability of extremophilic bacteria isolated from disturbed lands in the coal-mining region. We isolated microorganisms from disturbed lands and studied their cultural, morphological, and biochemical properties. Then, we determined their ability to synthesize indole-3-acetic acids. The extremophilic bacteria were identified and subjected to biocompatibility testing by co-cultivation. Next, we created consortia of pure cultures and analyzed biomass growth. Finally, the biopreparation was experimentally tested on Trifolium prantense L. seeds. We isolated 10 strains of microorganisms that synthesized 4.39 to 16.32 mg/mL of indole-3-acetic acid. The largest amounts of the acid were produced by Pantoea spp., Enterococcus faecium, Leclercia spp., Rothia endophytica, and Klebsiella oxytoca. A consortium of Pantoea spp., E. faecium, and R. endophytica at a ratio of 1:1:1 produced the largest amount of indole-3-acetic acid (15.59 mg/mL) and accumulated maximum biomass. The addition of 0.2% L-tryptophan to the nutrient medium increased the amount of indole-3-acetic acid to 18.45 mg/mL. When the T. prantense L. seeds were soaked in the biopreparation (consortium’s culture fluid) at a concentration of 2.5, the sprouts were 1.4 times longer on the 10th day of growth, compared to the control. The consortium of Pantoea spp., E. faecium, and R. endophytica (1:1:1) stimulated the growth of T. prantense L. seeds. Our findings can be further used to develop biofertilizers for agriculture.

Application of nickel chitosan nanoconjugate as an antifungal agent for combating Fusarium rot of wheat

Agro-researchers are endlessly trying to derive a potential biomolecule having antifungal properties in order to replace the application of synthetic fungicides on agricultural fields. Rot disease often caused by Fusarium solani made severe loss of wheat crops every year. Chitosan and its metallic nano-derivatives hold a broad-spectrum antifungal property. Our interdisciplinary study deals with the application of nickel chitosan nanoconjugate (NiCNC) against Fusarium rot of wheat, in comparison with chitosan nanoparticles (CNPs) and commercial fungicide Mancozeb. CNPs and NiCNC were characterized on the basis of UV–Vis spectrophotometry, HR-TEM, FESEM, EDXS and FT-IR. Both CNPs and NiCNC were found effective against the fungal growth, of which NiCNC at 0.04 mg/mL showed complete termination of F. solani grown in suitable medium. Ultrastructural analysis of F. solani conidia treated with NiCNC revealed pronounced damages and disruption of the membrane surface. Fluorescence microscopic study revealed generation of oxidative stress in the fungal system upon NiCNC exposure. Moreover, NiCNC showed reduction in rot disease incidence by 83.33% of wheat seedlings which was further confirmed through the observation of anatomical sections of the stem. NiCNC application helps the seedling to overcome the adverse effect of pathogen, which was evaluated through stress indices attributes.

Chitosan as a potential natural compound to manage plant diseases

The necessity for non-chemical approaches has grown as awareness of the dangers posed by pesticides has spread. Chitosan, due to its biocompatibility, biodegradability, and bioactivity is one the effective choice in phytopathology. Chitosan is a biopolymer that reduces plant diseases through two main mechanisms: (1) Direct antimicrobial function against pathogens, including plasma membrane damage mechanisms, interactions with DNA and RNA (electrostatic interactions), metal chelating capacity, and deposition onto the microbial surface, (2) Induction of plant defense responses resulting from downstream signalling, transcription factor activation, gene transcription and finally cellular activation after recognition and binding of chitin and chitosan by cell surface receptors. This biopolymer have potential with capability to combating fungi, bacteria, and viruses phythopathogens. Chitosan is synthesized by deacetylating chitin. The degree of deacetylation and molecular weight of chitosan are variable and have been mentioned as important structural parameters in chitosan's biological properties. Chitosan with a higher degree of deacetylation (>70 %) has better biological properties. Many crops able to withstand pre- and post-harvest illnesses better after receiving chitosan as a seed treatment, soil amendment, or foliar spray. This review discussed the properties and use of chitosan and focuses on its application as a plant resistance inducer against pathogens.

Recent development in nanoencapsulation and delivery of natural bioactives through chitosan scaffolds for various biological applications

Nowadays, nano/micro-encapsulation as a pioneering technique may significantly improve the bioavailability and durability of Natural bioactives. For this purpose, chitosan as a bioactive cationic natural polysaccharide has been frequently used as a carrier because of its distinct chemical and biological properties, including polycationic nature, biocompatibility, and biodegradability. Moreover, polysaccharide-based nano/micro-formulations are a new and extensive trend in scientific research and development in the disciplines of biomedicine, bioorganic/ medicinal chemistry, pharmaceutics, agrochemistry, and the food industry. It promises a new paradigm in drug delivery systems and nanocarrier formulations. This review aims to summarize current developments in approaches for designing innovative chitosan micro/nano-matrix, with an emphasis on the encapsulation of natural bioactives. The special emphasis led to a detailed integrative scientific achievement of the functionalities and abilities for encapsulating natural bioactives and mechanisms regulated in vitro/in vivo release in various biological/physiological environments.

Eco-friendly application of nano-chitosan for controlling potato and tomato bacterial wilt

Bacterial wilt is one of the main diseases of Solanum spp., which caused by Ralstonia solanacearum (RS), formerly known as Pseudomonas solanacearum. Different concentrations of chitosan nanoparticles have been evaluated as one of the alternative methods of disease management in vitro and in vivo to reduce the risks of pesticide residues. Results in vitro experiment indicated that RS5 isolate was the most virulence one compared to RS1 and RS3. Increasing concentration of nano-chitosan, lead to increase inhibition zone, and this was observed at higher concentrations (100 and 200 µg/ml). In vivo results showed the highest concentration of spraying chitosan nanoparticles increase percentage reduction of disease incidence and severity, in effected potato and tomato plants. Recorded data of disease incidence and severity in treated potato plants were 78.93% and 71.85%, while on tomato plants were 81.64% and 77.63%, respectively compared to untreated infected potato plants were recorded 15.38%, 20.87%, and tomato plants were 20.98% and 28.64%. Results also revealed that 100 µg/ml of chitosan nanoparticles the lowest treatments used as soil amended curative treatments led to incease percentage reduction of disease incidence and severity, respectively on potato and tomato plants, but less than preventive treatment. The results registered that on potato plant were 54.93% and 52.65%, whilst recorded on tomato plants were 59.93% and 56.74%. Transmission electron microscopy (TEM) micrpgraphs illustrated that morphological of healthy R. solanacearum cells were undesirably stained with uranyl. The electron-dense uranyl acetate dye was limited to the cell surface slightly than the cytoplasm, which designated the integrity of the cell film of healthy cells. While bacterial cells treated with nano-chitosan, showed modification in the external shape, such as lysis of the cell wall and loss of cell flagella. Also, the result of using Random amplified polymorphic DNA (RAPD)-PCR observed that differences in treated Ralstonia solanancearum genotype by nano-chitosan compared to the genotype of the same untreated isolate.

Biopolymer-based nanocarriers for sustained release of agrochemicals: A review on materials and social science perspectives for a sustainable future of agri- and horticulture

Devastating plant diseases and soil depletion rationalize an extensive use of agrochemicals to secure the food production worldwide. The sustained release of fertilizers and pesticides in agriculture is a promising solution to the eco-toxicological impacts and it might reduce the amount and increase the effectiveness of agrochemicals administration in the field. This review article focusses on carriers with diameters below 1 μm, such as capsules, spheres, tubes and micelles that promote the sustained release of actives. Biopolymer nanocarriers represent a potentially environmentally friendly alternative due to their renewable origin and biodegradability, which prevents the formation of microplastics. The social aspects, economic potential, and success of commercialization of biopolymer based nanocarriers are influenced by the controversial nature of nanotechnology and depend on the use case. Nanotechnology's enormous innovative power is only able to unfold its potential to limit the effects of climate change and to counteract current environmental developments if the perceived risks are understood and mitigated.

Nitric oxide-releasing nanomaterials: from basic research to potential biotechnological applications in agriculture

Nitric oxide (NO) is a multifunctional gaseous signal that modulates the growth, development and stress tolerance of higher plants. NO donors have been used to boost plant endogenous NO levels and to activate NO-related responses, but this strategy is often hindered by the relative instability of donors. Alternatively, nanoscience offers a new, promising way to enhance NO delivery to plants, as NO-releasing nanomaterials (e.g. S-nitrosothiol-containing chitosan nanoparticles) have many beneficial physicochemical and biochemical properties compared to non-encapsulated NO donors. Nano NO donors are effective in increasing tissue NO levels and enhancing NO effects both in animal and human systems. The authors believe, and would like to emphasize, that new trends and technologies are essential for advancing plant NO research and nanotechnology may represent a breakthrough in traditional agriculture and environmental science. Herein, we aim to draw the attention of the scientific community to the potential of NO-releasing nanomaterials in both basic and applied plant research as alternatives to conventional NO donors, providing a brief overview of the current knowledge and identifying future research directions. We also express our opinion about the challenges for the application of nano NO donors, such as the environmental footprint and stakeholder's acceptance of these materials.

Silica nanoparticles protect rice against biotic and abiotic stresses

BACKGROUND

By 2050, the world population will increase to 10 billion which urged global demand for food production to double. Plant disease and land drought will make the situation more dire, and safer and environment-friendly materials are thus considered as a new countermeasure. The rice blast fungus, Magnaporthe oryzae, causes one of the most destructive diseases of cultivated rice worldwide that seriously threatens rice production. Unfortunately, traditional breeding nor chemical approaches along control it well. Nowadays, nanotechnology stands as a new weapon against these mounting challenges and silica nanoparticles (SiO₂ NPs) have been considered as potential new safer agrochemicals recently but the systematically studies remain limited, especially in rice.

RESULTS

Salicylic acid (SA) is a key plant hormone essential for establishing plant resistance to several pathogens and its further affected a special form of induced resistance, the systemic acquired resistance (SAR), which considered as an important aspect of plant innate immunity from the locally induced disease resistance to the whole plant. Here we showed that SiO₂ NPs could stimulate plant immunity to protect rice against M. oryzae through foliar treatment that significantly decreased disease severity by nearly 70% within an appropriate concentration range. Excessive concentration of foliar treatment led to disordered intake and abnormal SA responsive genes expressions which weaken the plant resistance and even aggravated the disease. Importantly, this SA-dependent fungal resistance could achieve better results with root treatment through a SAR manner with no phytotoxicity since the orderly and moderate absorption. What's more, root treatment with SiO₂ NPs could also promote root development which was better to deal with drought.

CONCLUSIONS

Taken together, our findings not only revealed SiO₂ NPs as a potential effective and safe strategy to protect rice against biotic and abiotic stresses, but also identify root treatment for the appropriate application method since it seems not causing negative effects and even have promotion on root development.

Chitosan thiamine nanoparticles intervene innate immunomodulation during Chickpea-Fusarium interaction

The present study evaluated the effect of chitosan thiamine nanoparticles (TCNP) on the activation of defence responses in chickpea against stress caused by wilt pathogen, Fusarium oxysporum f. sp. ciceri (FOC), under greenhouse condition. A significant increase in enzymatic and non-enzymatic antioxidants was observed in the TCNP treated chickpea plants challenged with FOC compared to the untreated control. Histochemical staining showed high deposition of lignin in the vascular bundles of chickpea stem tissues in TCNP treated plants challenged with FOC. More than 90% protection against wilt pathogen was observed in TCNP treated chickpea plants challenged with FOC, under greenhouse condition. Higher accumulation of antioxidants and phenylpropanoids in TCNP treated challenged chickpea plants well correlates with resistance against wilt pathogen. These results suggest that the elicitation of stress response in TCNP treated chickpea during FOC interaction play a vital role in suppressing the wilt disease in chickpea.

Antimicrobial Food Packaging Based on Prodigiosin-Incorporated Double-Layered Bacterial Cellulose and Chitosan Composites

Nowadays, food packaging systems have shifted from a passive to an active role in which the incorporation of antimicrobial compounds into biopolymers can promote a sustainable way to reduce food spoilage and its environmental impact. Accordingly, composite materials based on oxidized-bacterial cellulose (BC) and poly(vinyl alcohol)-chitosan (PVA-CH) nanofibers were produced by needleless electrospinning and functionalized with the bacterial pigment prodigiosin (PG). Two strategies were explored, in the first approach PG was incorporated in the electrospun PVA-CH layer, and TEMPO-oxidized BC was the substrate for nanofibers deposition (BC/PVA-CH_PG composite). In the second approach, TEMPO-oxidized BC was functionalized with PG, and afterward, the PVA-CH layer was electrospun (BC_PG/PVA-CH composite). The double-layer composites obtained were characterized and the nanofibrous layers displayed smooth fibers with average diameters of 139.63 ± 65.52 nm and 140.17 ± 57.04 nm, with and without pigment incorporation, respectively. FTIR-ATR analysis confirmed BC oxidation and revealed increased intensity at specific wavelengths, after pigment incorporation. Moreover, the moderate hydrophilic behavior, as well as the high porosity exhibited by each layer, remained mostly unaffected after PG incorporation. The composites’ mechanical performance and the water vapor transmission rate (WVTR) evaluation indicated the suitability of the materials for certain food packaging solutions, especially for fresh products. Additionally, the red color provided by the bacterial pigment PG on the external surface of a food packaging material is also a desirable effect, to attract the consumers’ attention, creating a multifunctional material. Furthermore, the antimicrobial activity was evaluated and, PVA-CH_PG, and BC_PG layers exhibited the highest antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Thus, the fabricated composites can be considered for application in active food packaging, owing to PG antimicrobial potential, to prevent foodborne pathogens (with PG incorporated into the inner layer of the food packaging material, BC/PVA-CH_PG composite), but also to prevent external contamination, by tackling the exterior of food packaging materials (with PG added to the outer layer, BC_PG/PVA-CH composite).

Biocontrol Potential of Chitin and Chitosan Extracted from Black Soldier Fly Pupal Exuviae against Bacterial Wilt of Tomato

Globally, Ralstonia solanacearum (Smith) is ranked one of the most destructive bacterial pathogens inducing rapid and fatal wilting symptoms on tomatoes. Yield losses on tomatoes vary from 0 to 91% and most control measures are unaffordable to resource-poor farmers. This study investigated the antimicrobial activities of chitin and chitosan extracted from black soldier fly (BSF) pupal exuviae against R. solanacearum. Morphological, biochemical, and molecular techniques were used to isolate and characterize R. solanacearum for in vitro pathogenicity test using disc diffusion technique. Our results revealed that BSF chitosan significantly inhibited the growth of R. solanacearum when compared to treatments without chitosan. However, there was no significant difference in the antibacterial activities between BSF and commercial chitosan against R. solanacearum. Soil amended with BSF-chitin and chitosan demonstrated a reduction in bacterial wilt disease incidence by 30.31% and 34.95%, respectively. Whereas, disease severity was reduced by 22.57% and 23.66%, when inoculated tomato plants were subjected to soil amended with BSF chitin and chitosan, respectively. These findings have demonstrated that BSF pupal shells are an attractive renewable raw material for the recovery of valuable products (chitin and chitosan) with promising ability as a new type of eco-friendly control measure against bacterial wilt caused by R. solanacearum. Further studies should explore integrated pest management options that integrate multiple components including insect-based chitin and chitosan to manage bacterial wilt diseases, contributing significantly to increased tomato production worldwide.

Recent Advances in Plant Nanoscience

Plants have complex internal signaling pathways to quickly adjust to environmental changes and harvest energy from the environment. Facing the growing population, there is an urgent need for plant transformation and precise monitoring of plant growth to improve crop yields. Nanotechnology, an interdisciplinary research field, has recently been boosting plant yields and meeting global energy needs. In this context, a new field, "plant nanoscience," which describes the interaction between plants and nanotechnology, emerges as the times require. Nanosensors, nanofertilizers, nanopesticides, and nano-plant genetic engineering are of great help in increasing crop yields. Nanogenerators are helping to develop the potential of plants in the field of energy harvesting. Furthermore, the uptake and internalization of nanomaterials in plants and the possible effects are also worthy of attention. In this review, a forward-looking perspective on the plant nanoscience is presented and feasible solutions for future food shortages and energy crises are provided.

Inhibitory Effect of Chitosan and Phosphate Cross-linked Chitosan against Cucumber Mosaic Virus and Pepper Mild Mottle Virus

Cucumber mosaic virus (CMV) and Pepper mild mottle virus (PMMoV) causes severe economic loss in crop productivity of both agriculture and horticulture crops in Korea. The previous surveys showed that naturally available biopolymer material - chitosan (CS), which is from shrimp cells, reduced CMV accumulation on pepper. To improve the antiviral activity of CS, it was synthesized to form phosphate cross-linked chitosan (PCS) and compared with the original CS. Initially, the activity of CS and PCS (0.01%, 0.05%, and 0.1% concentration) compound against PMMoV infection and replication was tested using a half-leaf assay on Nicotiana glutinosa leaves. The total number of local lesions represented on a leaf of N. glutinosa were counted and analyzed with phosphate buffer treated leaves as a negative control. The leaves treated with a 0.1% concentration of CS or PCS compounds exhibited an inhibition effect by 40-75% compared with the control leaves. The same treatment significantly reduced about 40% CMV accumulation measured by double antibody sandwich enzyme-linked immunosorbent assay and increased the relative expression levels of the NPR1, PR-1, cysteine protease inhibitor gene, LOX, PAL, SRC2, CRF3 and ERF4 genes analyzed by quantitative reverse transcriptase-polymerase chain reaction, in chili pepper plants.

Effect of Foliar Fertigation of Chitosan Nanoparticles on Cadmium Accumulation and Toxicity in Solanum lycopersicum

Simple Summary

The experiment conducted on Solanum lycopersicum provided an insight about Cd uptake, and the way a Solanum lycopersicum changes its physiological, biochemical and morphological responses when CTS-NPs are administered against Cd. As an effective important polymer, CTS-NPs enhanced the plant biomass, SPAD index, photosynthetic rate, and protein content in the Solanum lycopersicum plants grown in Cd stress, as a study herein. Addition of CTS-NPs reduced Cd accumulation by increasing the nutrient uptake. Furthermore, CTS-NPs treatment enhances tolerance to Cd stress through hampering ROS production accompanied by H₂O₂ activity, through reducing the peroxidation of lipids by minimizing MDA content, and through improving enzymatic (CAT, POX, SOD), non-enzymatic (GSH and AsA), and osmoprotectants (proline) antioxidant contents that are considered as a first line of defense to protect plants from stress.

Abstract

Cadmium (Cd) stress is increasing at a high pace and is polluting the agricultural land. As a result, it affects animals and the human population via entering into the food chain. The aim of this work is to evaluate the possibility of amelioration of Cd stress through chitosan nanoparticles (CTS-NPs). After 15 days of sowing (DAS), Solanum lycopersicum seedlings were transplanted into maintained pots (20 in number). Cadmium (0.8 mM) was providing in the soil as CdCl₂·2.5H₂O at the time of transplanting; however, CTS-NPs (100 µg/mL) were given through foliar spray at 25 DAS. Data procured from the present experiment suggests that Cd toxicity considerably reduces the plant morphology, chlorophyll fluorescence, in addition to photosynthetic efficiency, antioxidant enzyme activity and protein content. However, foliar application of CTS-NPs was effective in increasing the shoot dry weight (38%), net photosynthetic rate (45%) and SPAD index (40%), while a decrease in malondialdehyde (24%) and hydrogen peroxide (20%) was observed at the 30 DAS stage as compared to control plants. On behalf of the current results, it is demonstrated that foliar treatment of CTS-NPs might be an efficient approach to ameliorate the toxic effects of Cd.

Endophytic Nanotechnology: An Approach to Study Scope and Potential Applications

Nanotechnology has become a very advanced and popular form of technology with huge potentials. Nanotechnology has been very well explored in the fields of electronics, automobiles, construction, medicine, and cosmetics, but the exploration of nanotecnology's use in agriculture is still limited. Due to climate change, each year around 40% of crops face abiotic and biotic stress; with the global demand for food increasing, nanotechnology is seen as the best method to mitigate challenges in disease management in crops by reducing the use of chemical inputs such as herbicides, pesticides, and fungicides. The use of these toxic chemicals is potentially harmful to humans and the environment. Therefore, using NPs as fungicides/ bactericides or as nanofertilizers, due to their small size and high surface area with high reactivity, reduces the problems in plant disease management. There are several methods that have been used to synthesize NPs, such as physical and chemical methods. Specially, we need ecofriendly and nontoxic methods for the synthesis of NPs. Some biological organisms like plants, algae, yeast, bacteria, actinomycetes, and fungi have emerged as superlative candidates for the biological synthesis of NPs (also considered as green synthesis). Among these biological methods, endophytic microorganisms have been widely used to synthesize NPs with low metallic ions, which opens a new possibility on the edge of biological nanotechnology. In this review, we will have discussed the different methods of synthesis of NPs, such as top-down, bottom-up, and green synthesis (specially including endophytic microorganisms) methods, their mechanisms, different forms of NPs, such as magnesium oxide nanoparticles (MgO-NPs), copper nanoparticles (Cu-NPs), chitosan nanoparticles (CS-NPs), β-d-glucan nanoparticles (GNPs), and engineered nanoparticles (quantum dots, metalloids, nonmetals, carbon nanomaterials, dendrimers, and liposomes), and their molecular approaches in various aspects. At the molecular level, nanoparticles, such as mesoporous silica nanoparticles (MSN) and RNA-interference molecules, can also be used as molecular tools to carry genetic material during genetic engineering of plants. In plant disease management, NPs can be used as biosensors to diagnose the disease.

Transition metal oxide and chalcogenide-based nanomaterials for antibacterial activities: an overview

A new battle line is drawn where antibiotic misuse and mismanagement have made treatment of bacterial infection a thorny issue. It is highly desirable to develop active antibacterial materials for bacterial control and destruction without drug resistance. A large amount of effort has been devoted to transition metal oxide and chalcogenide (TMO&C) nanomaterials as possible candidates owing to their unconventional physiochemical, electronic and optical properties and feasibility of functional architecture assembly. This review expounds multiple TMO&C-based strategies to combat pathogens, opening up new possibilities for the design of simple, yet highly effective systems that are crucial for antimicrobial treatment. A special emphasis is placed on the multiple mechanisms of these nanoagents, including mechanical rupture, photocatalytic/photothermal activity, Fenton-type reaction, nanozyme-assisted effect, released metal ions and the synergistic action of TMO&C in combination with other antibacterial agents. The applications of TMO&C nanomaterials mostly in air/water purification and wound healing along with their bactericidal activities and mechanisms are also described. Finally, the contemporary challenges and trends in the development of TMO&C-based antibacterial strategies are proposed.

Nanometerization of thiamethoxam by a cationic star polymer nanocarrier efficiently enhances the contact and plant-uptake dependent stomach toxicity against green peach aphids

BACKGROUND

The utilization efficiency of conventional insecticides is comparatively low in agricultural production, which leads to their excessive application and environmental pollution. Insecticide nanometerization by polymers and polymeric materials has advantages, particularly increased utilization efficiency and reduced insecticide application.

RESULTS

To increase the utilization efficiency of insecticides, a star polycation (SPc) was selected as a drug carrier that could be complexed with thiamethoxam through electrostatic interaction. Formation of the complex decreased the particle size of thiamethoxam from 575.77 to 116.16 nm in aqueous solution. Plant uptake of SPc-delivered thiamethoxam was increased 1.69-1.84 times compared with thiamethoxam alone. Nano-sized thiamethoxam/SPc complexes showed enhanced contact and stomach toxicity against green peach aphids.

CONCLUSION

SPc is a promising insecticide adjuvant for insecticide nanometerization, and is beneficial in improving insecticidal activity and decreasing the application amounts and application rates of conventional insecticides. © 2020 Society of Chemical Industry.

Oregano (Origanum vulgar subsp. viride) Essential Oil: Extraction, Preparation, Characterization, and Encapsulation by Chitosan-Carbomer Nanoparticles for Biomedical Application

Background: Plant essential oils (EOs) as natural agents have broad activities, including antibacterial, antifungal, antiviral, insecticidal, and repel activities because of their chemical compositions. Objectives: The objective of this study was to increase the stability of Origanum vulgar subsp. viride EOs by encapsulation in chitosan-carbomer nanoparticles by ionic gelation method. Methods: The EOs from dried leaves of O. vulgar subsp. viride were extracted by hydro-distillation method, and EO components were determined by gas chromatography-mass spectrometry (GC-MS). Besides, OEO-loaded chitosan (CS) nano-capsules were prepared using the ionic gelation method. The molecular structure and morphology of nanoparticles were characterized by Fourier Transform-Infrared (FTIR) and scanning electron microscopy (SEM), respectively. The encapsulation efficiency (EE), loading capacity (LC) of the OEO-loaded CS nanoparticles, and their release profiles were determined using UV/Vis spectrophotometry. Results: The major components of OEO were thymol (20.53%), 4-terpinenol (20.28%), and γ-terpinene (12.22%). The percentages of EE and LC of OEO ranged from 99.25 ± 0.74 to 93.84 ± 0.71 and 38.02 ± 0.18 to 66.73 ± 0.51, respectively, with increasing the OEO to chitosan ratio from 1:0.01 to 1:0.04 W/V. The nanoparticles were regular, uniform, and spherical in shape with an average size of 134 to 181 nm, which were dispersed throughout the solution. The zeta potential values for blank chitosan nanoparticles (CSNPs) and OEO-loaded CSNPs were +23.4 and +38.5 mV, respectively. Conclusions: The results confirmed the suitability of the CS-carbomer complex for OEO- CSNPs formation. It is recommended to evaluate the antimicrobial, insecticidal and insect repel activities of developed OEO nanoparticles in laboratory and field studies.

Current trends and challenges in the synthesis and applications of chitosan-based nanocomposites for plants: A review

Chitosan, a low-cost and multipurpose polymer with numerous desired physicochemical and biological properties has been tested for various applications in agriculture, pharmacy, and biomedicine industries. The availability of functional groups along the backbone makes chitosan readily available for other polymers and metal ions to form bio-nanocomposites. Different types of chitosan-based nanocomposites have been designed and tested for the enhancement of chitosan efficiency and ultimately widening the application areas of chitosan in plants. These nanocomposites serve different purposes such as eliciting plant's defence systems against different threats (pathogen attack), antimicrobial agent against bacteria, fungi and viruses, enhancement of nutrient uptake by plants, control release of micro/macronutrients, fungicides and herbicides. In this review, an extensive outlook has been provided (mainly in the last five years) to recent trends and advances in the fabrication and application of chitosan-based composites. Finally, current challenges and future development opportunities of chitosan-based nanocomposites for plants are discussed.

Recent advances in the applications of nano-agrochemicals for sustainable agricultural development

Modern agricultural practices have triggered the process of agricultural pollution. This process can cause the degradation of eco-systems, land, and environment owing to the modern-day by-products of agriculture. The substantial use of chemical fertilizers, pesticides, and, contaminated water for irrigation cause further damage to agriculture. The current scenario of the agriculture and food sector has therefore become unsustainable. Nanotechnology has provided innovative and resourceful frontiers to the agriculture sector by contributing practical applications in conventional agricultural ways and practices. There is a large possibility that agri-nanotechnology can have a significant impact on the sustainable agriculture and crop growth. Recent research has shown the potential of nanotechnology in improving the agriculture sector by enhancing the efficiency of agricultural inputs and providing solutions to agricultural problems for improving food productivity and security. The prospective use of nanoscale agrochemicals such as nanofertilizers, nanopesticides, nanosensors, and nanoformulations in agriculture has transformed traditional agro-practices, making them more sustainable and efficient. However, the application of these nano-products in real field situations raises concern about nanomaterial safety, exposure levels, and toxicological repercussions to the environment and human health. The present review gives an insight into recent advancements in nanotechnology-based agrochemicals that have revolutionized the agriculture sector. Further, the implementation barriers related to the nanomaterial use in agriculture, their commercialization potential, and the need for policy regulations to assess possible nano-agricultural risks are also discussed.

Chitosan-silicon nanofertilizer to enhance plant growth and yield in maize (Zea mays L.)

We report a novel chitosan-silicon nanofertilizer (CS-Si NF) wherein chitosan-tripolyphosphate (TPP) nano-matrix has been used to encapsulate silicon (Si) for its slow release. It was synthesied by ionic gelation method and characterized by dynamic light scattering (DLS), fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic absorption spectrophotometry (AAS). The developed CS-Si NF exhibited slow release of Si and promoted gowth and yield in maize crop. Seeds primed with different concentrations of CS-Si NF (0.04-0.12%, w/v) exhibited up to 3.7 fold increased seedling vigour index (SVI) as compared with SiO₂. Its foliar spray significantly induced antioxidant-defence enzymes' activities and equilibrated cellular redox homeostasis by balancing O₂^-1 and H₂O₂ content in leaf as compared with SiO₂. Application of nanofertilizer (0.01-0.16%, w/v) stirred total chlorophyll content (21.01-25.11 mg/g) and leaf area (159.34-166.96 cm²) to expedite photosynthesis as compared with SiO₂. In field experiment, 0.08% CS-Si NF resulted in 43.4% higher yield/plot and 0.04% concentration gave 45% higher test weight as compared with SiO₂. Fecund and myriad effects of developed nanofertilizer over SiO₂ could be attributed to slow/protective release of Si from nanofertilizer. Overall, results decipher the enormous potential of CS-Si NF for its use as a next generation nanofertilizer for sustainable agriculture.

Bioengineered chitosan-magnesium nanocomposite: A novel agricultural antimicrobial agent against Acidovorax oryzae and Rhizoctonia solani for sustainable rice production

Chitosan is a potent biopolymer having promising antimicrobial properties against phytopathogens. Recently, engineered nanomaterials (ENMs) have gained much attention due to their potential application in the plant disease management. In this study, we reported the green synthesis of chitosan-magnesium (CS-Mg) nanocomposite and its antimicrobial activity against two rice pathogens namely Acidovorax oryzae and Rhizoctonia solani for the first time. The green MgO nanoparticles synthesized by using a native Bacillus sp. strain RNT3, were used to fabricate CS-Mg nanocomposite utilizing one-pot synthesis method. The synthesis of CS-Mg nanocomposite was further confirmed by using UV-vis spectroscopy, whereas, FTIR and XRD analysis showed the capping of CS-Mg nanocomposites by different functional groups together with their crystalline structure, respectively. Besides, SEM and TEM images revealed the spherical shape along with the particles size ranging from 29 to 60 nm. Moreover, EDS analysis confirmed the elemental purity of nanocomposite. The CS-Mg nanocomposite showed remarkable antimicrobial activity against A. oryzae and R. solani and significantly inhibited the growth as compared to non-treated control. The ultrastructure studies showed damaged structure of cell wall and internal cellular organelles after treatment with 100 μg mL^-1 CS-Mg nanocomposite. The results of this study indicated that CS-Mg nanocomposite-based antimicrobial agents could be considered as promising nanopesticides against phytopathogens in plant disease management.

Applications of chitosan and chitosan based metallic nanoparticles in agrosciences-A review

The second most abundant biological macromolecule, next to cellulose is Chitosan. It is a versatile naturally occurring hydrophilic polysaccharide, derived as a deacetylated form of chitin. Due to its biocompatibility, biodegradability and antimicrobial activity, it has become a significant area of research towards drug delivery system, plant growth promotion, anti-pathogenic potentiality, seed priming and in plant defense mechanism. Various synthetic strategies have been established in recent years that couples different metals with chitosan nanoparticles. Metals like silver, copper, zinc, iron and nickel are highly compatible to form chitosan metallic nanoparticles and are proved to be non-toxic to the agricultural plant system. This review highlights the mode of action of nanochitosan on Gram-positive and Gram-negative bacteria in a distinguished manner as well as its action on fungi. A prime focus has been given on the skeletal framework of the metallic nanochitosan particles. Our study also projects the antimicrobial mechanism of chitosan based on its physiochemical properties, environmental factors and the type of organism on which it acts. Moreover, the mechanism for stimulation of plant immunity by metallic nanochitosan has also been reviewed. Our study relies on the conclusion that chitosan metallic nanoparticles showed enhanced anti-pathogenic and plant growth promoting activity in comparison to bulk chitosan.

Chitin and Chitosan Fragments Responsible for Plant Elicitor and Growth Stimulator

Chitin and chitosan are natural polysaccharides with huge application potential in agriculture, such as promoting plant growth, eliciting plant resistance against biotic and abiotic stress, and activating symbiotic signaling between plants and beneficial microorganisms. Chitin and chitosan offer a sustainable alternative for future crop production. The bioactivities of chitin and chitosan closely depend on their structural factors, including molecular size, degree of acetylation, and pattern of acetylation. It is of great significance to identify the key fragments in chitin and chitosan chains that are responsible for these agricultural bioactivities. Herein, we review the recent progress in the structure-function relationship of chitin and chitosan in the field of agriculture application. The preparation of chitin and chitosan fragments and their action mode for plant protection and growth are also discussed.