Chitosan Nanoparticles Inactivate Alfalfa Mosaic Virus Replication and Boost Innate Immunity in Nicotiana glutinosa Plants

Biofabricated nanomaterials in sustainable agriculture: insights, challenges and prospects

One ever-evolving and ever-demanding critical human endeavour is the provision of food security for the growing world population. This can be done by adopting sustainable agriculture through horizontal (expanding the arable land area) and vertical (intensifying agriculture through sound technological approaches) interventions. Customized formulated nanomaterials have numerous advantages. With their specialized physico-chemical properties, some nanoparticulated materials improve the plant's natural development and stress tolerance and some others are good nanocarriers. Nanocarriers in agriculture often coat chemicals to form composites having utilities with crop productivity enhancement abilities, environmental management (such as ecotoxicity reduction ability) and biomedicines (such as the ability to control and target the release of useful nanoscale drugs). Ag, Fe, Zn, TiO2, ZnO, SiO2and MgO nanoparticles (NPs), often employed in advanced agriculture, are covered here. Some NPs used for various extended purposes in modern farming practices, including disease diagnostics and seed treatment are also covered. Thus, nanotechnology has revolutionized agrotechnology, which holds promise to transform agricultural (ecosystems as a whole to ensure food security in the future. Considering the available literature, this article further probes the emergent regulatory issues governing the synthesis and use of nanomaterials in the agriculture sector. If applied responsibly, nanomaterials could help improve soil health. This article provides an overview of the nanomaterials used in the distribution of biomolecules, to aid in devising a safer and eco-friendly sustainable agriculture strategy. Through this, agri-systems that depend on advanced farming practices might function more effectively and enhance agri-productivity to meet the food demand of the rising world population.

Foliar Application of Rhizobium leguminosarum bv. viciae Strain 33504-Borg201 Promotes Faba Bean Growth and Enhances Systemic Resistance Against Bean Yellow Mosaic Virus Infection

The bean yellow mosaic virus (BYMV) is one of the most serious economic diseases affecting faba bean crop production. Rhizobium spp., well known for its high nitrogen fixation capacity in legumes, has received little study as a possible biocontrol agent and antiviral. Under greenhouse conditions, foliar application of molecularly characterized Rhizobium leguminosarum bv. viciae strain 33504-Borg201 to the faba bean leaves 24 h before they were infected with BYMV made them much more resistant to the disease while also lowering its severity and accumulation. Furthermore, the treatment promoted plant growth and health, as evidenced by the increased total chlorophyll (32.75 mg/g f.wt.) and protein content (14.39 mg/g f.wt.), as well as the improved fresh and dry weights of the plants. The protective effects of 33504-Borg201 greatly lowered the levels of hydrogen peroxide (H2O2) (4.92 µmol/g f.wt.) and malondialdehyde (MDA) (173.72 µmol/g f.wt.). The antioxidant enzymes peroxidase (1.58 µM/g f.wt.) and polyphenol oxidase (0.57 µM/g f.wt.) inhibited the development of BYMV in plants treated with 33504-Borg201. Gene expression analysis showed that faba bean plants treated with 33504-Borg201 had higher amounts of pathogenesis-related protein-1 (PR-1) (3.28-fold) and hydroxycinnamoyl-CoA quinate hydroxycinnamoyltransferase (4.13-fold) than control plants. These findings demonstrate the potential of 33,504-Borg201 as a cost-effective and eco-friendly method to protect faba bean plants against BYMV. Implementing this approach could help develop a simple and sustainable strategy for protecting faba bean crops from the devastating effects of BYMV.

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.

Chitosan nanocomposites as a nano-bio tool in phytopathogen control

Chitosan, an economically viable and versatile biopolymer, exhibits a wide array of advantageous physicochemical and biological properties. Chitosan nanocomposites, formed by the amalgamation of chitosan or chitosan nanoparticles with other nanoparticles or materials, have garnered extensive attention across agricultural, pharmaceutical, and biomedical domains. These nanocomposites have been rigorously investigated due to their diverse applications, notably in combatting plant pathogens. Their remarkable efficacy against phytopathogens has positioned them as a promising alternative to conventional chemical-based methods in phytopathogen control, thus exploring interest in sustainable agricultural practices with reduced reliance on chemical interventions. This review aims to highlight the anti-phytopathogenic activity of chitosan nanocomposites, emphasizing their potential in mitigating plant diseases. Additionally, it explores various synthesis methods for chitosan nanoparticles to enhance readers' understanding. Furthermore, the analysis delves into elucidating the intricate mechanisms governing the antimicrobial effectiveness of these composites against bacterial and fungal phytopathogens.

Application of nanoparticles for management of plant viral pathogen: Current status and future prospects

Plant viruses are responsible for nearly 47 % of all crop losses brought by plant diseases, which have a considerable negative impact on agricultural output. Nanoparticles have the potential to greatly raise agricultural output due to their wonderful applications in the fields of highly sensitive biomolecular detection, disease diagnostics, antimicrobials, and therapeutic compounds. The application of nanotechnology in plant virology is known as nanophytovirology, and it involves biostimulation, drug transport, genetic manipulation, therapeutic agents, and induction of plant defenses. The inactivation and denaturation of capsid protein, nucleic acids (RNA or DNA), and other protein constituents are involved in the underlying mechanism. To determine the precise mechanism by which nanoparticles affect viral mobility, reproduction, encapsidation, and transmission, more research is however required. Nanoparticles can be used to precisely detect plant viruses using nanobiosensors or as biostimulants. The varieties of nanoparticles employed in plant virus control and their methods of virus suppression are highlighted in this review.

Review on interactions between nanomaterials and phytohormones: Novel perspectives and opportunities for mitigating environmental challenges

Nanotechnology offers the potential to provide innovative solutions for sustainable crop production as plants are exposed to a combination of climate change factors (CO2, temperature, UV radiation, ozone), abiotic (heavy metals, salinity, drought), and biotic (virus, bacteria, fungi, nematode, and insects) stresses. The application of particular sizes, shapes, and concentration of nanomaterials (NMs) potentially mitigate the negative impacts in plants by modulation of photosynthetic rate, redox homeostasis, hormonal balance, and nutrient assimilation through upregulation of anti-stress metabolites, antioxidant defense pathways, and genes and genes network. The present review inculcates recent advances in uptake, translocation, and accumulation mechanisms of NMs in plants. The critical theme of this review provides detailed insights into different physiological, biochemical, molecular, and stress tolerance mechanism(s) of NMs action and their cross-talk with different phytohormones. The role of NMs as a double-edged sword for climate change factors, abiotic, and biotic stresses for nutrients uptake, hormones synthesis, cytotoxic, and genotoxic effects including chromosomal aberration, and micronuclei synthesis have been extensively studied. Importantly, this review aims to provide an in-depth understanding of the hormesis effect at low and toxicity at higher doses of NMs under different stressors to develop innovative approaches and design smart NMs for sustainable crop production.

Antiviral functionalization of cellulose using tannic acid and tannin-rich extracts

Due to seasonally appearing viruses and several outbreaks and present pandemic, we are surrounded by viruses in our everyday life. In order to reduce viral transmission, functionalized surfaces that inactivate viruses are in large demand. Here the endeavor was to functionalize cellulose-based materials with tannic acid (TA) and tannin-rich extracts by using different binding polymers to prevent viral infectivity of both non-enveloped coxsackievirus B3 (CVB3) and enveloped human coronavirus OC43 (HCoV-OC43). Direct antiviral efficacy of TA and spruce bark extract in solution was measured: EC50 for CVB3 was 0.12 and 8.41 μg/ml and for HCoV-OC43, 78.16 and 95.49 μg/ml, respectively. TA also led to an excellent 5.8- to 7-log reduction of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus infectivity. TA functionalized materials reduced infectivity already after 5-min treatment at room temperature. All the tested methods to bind TA showed efficacy on paperboard with 0.1 to 1% (w/v) TA concentrations against CVB3 whereas material hydrophobicity decreased activities. Specific signatures for TA and HCoV-OC43 were discovered by Raman spectroscopy and showed clear co-localization on the material. qPCR study suggested efficient binding of CVB3 to the TA functionalized cellulose whereas HCoV-OC43 was flushed out from the surfaces more readily. In conclusion, the produced TA-materials showed efficient and broadly acting antiviral efficacy. Additionally, the co-localization of TA and HCoV-OC43 and strong binding of CVB3 to the functionalized cellulose demonstrates an interaction with the surfaces. The produced antiviral surfaces thus show promise for future use to increase biosafety and biosecurity by reducing pathogen persistence.

Nanoplatforms for the Delivery of Nucleic Acids into Plant Cells

Nanocarriers are widely used for efficient delivery of different cargo into mammalian cells; however, delivery into plant cells remains a challenging issue due to physical and mechanical barriers such as the cuticle and cell wall. Here, we discuss recent progress on biodegradable and biosafe nanomaterials that were demonstrated to be applicable to the delivery of nucleic acids into plant cells. This review covers studies the object of which is the plant cell and the cargo for the nanocarrier is either DNA or RNA. The following nanoplatforms that could be potentially used for nucleic acid foliar delivery via spraying are discussed: mesoporous silica nanoparticles, layered double hydroxides (nanoclay), carbon-based materials (carbon dots and single-walled nanotubes), chitosan and, finally, cell-penetrating peptides (CPPs). Hybrid nanomaterials, for example, chitosan- or CPP-functionalized carbon nanotubes, are taken into account. The selected nanocarriers are analyzed according to the following aspects: biosafety, adjustability for the particular cargo and task (e.g., organelle targeting), penetration efficiency and ability to protect nucleic acid from environmental and cellular factors (pH, UV, nucleases, etc.) and to mediate the gradual and timely release of cargo. In addition, we discuss the method of application, experimental system and approaches that are used to assess the efficiency of the tested formulation in the overviewed studies. This review presents recent progress in developing the most promising nanoparticle-based materials that are applicable to both laboratory experiments and field applications.

Protective Activity of Rhizobium leguminosarum bv. viciae Strain 33504-Mat209 against Alfalfa Mosaic Virus Infection in Faba Bean Plants

The application of Rhizobium spp., nitrogen-fixing plant growth-promoting rhizobacteria, as biocontrol agents to enhance systemic disease resistance against plant viral infections is a promising approach towards achieving sustainable and eco-friendly agriculture. However, their potential as antivirals and biocontrol agents is less studied. Herein, the capability of Rhizobium leguminosarum bv. viciae strain 33504-Mat209 was evaluated to promote plant growth and enhance faba bean systemic resistance against alfalfa mosaic virus (AMV) infection. Under greenhouse conditions, the soil inoculation with 3504-Mat209 resulted in notable improvements in growth and an increase in chlorophyll content. This led to a marked decrease in the disease incidence, severity, and viral accumulation level by 48, 74, and 87%, respectively. The protective effect of 33504-Mat209 was linked to significant decreases in non-enzymatic oxidative stress indicators, specifically H₂O₂ and MDA. Additionally, there were significant increases in the activity of reactive oxygen species scavenging enzymes, such as peroxidase (POX) and polyphenol oxidase (PPO), compared to the virus treatment. The elevated transcript levels of polyphenolic pathway genes (C₄H, HCT, C₃H, and CHS) and pathogenesis-related protein-1 were also observed. Out of 18 detected compounds, HPLC analysis revealed that 33504-Mat209-treated plants increased the accumulation of several compounds, such as gallic acid, chlorogenic acid, catechin, pyrocatechol, daidzein, quercetin, and cinnamic acid. Therefore, the ability of 33504-Mat209 to promote plant growth and induce systemic resistance against AMV infection has implications for utilizing 33504-Mat209 as a fertilizer and biocontrol agent. This could potentially introduce a new strategy for safeguarding crops, promoting sustainability, and ensuring environmental safety in the agricultural sector. As far as we know, this is the first study of biological control of AMV mediated by Rhizobium spp. in faba bean plants.

Antiviral Activity of Chitosan Nanoparticles and Chitosan Silver Nanocomposites against Alfalfa Mosaic Virus

Plant viruses are a global concern for sustainable crop production. Among the currently available antiviral approaches, nanotechnology has been overwhelmingly playing an effective role in circumventing plant viruses. Alfalfa mosaic virus (AMV) was isolated and identified from symptomatic pepper plants in Egypt using symptomatology, serological tests using the direct ELISA technique, differential hosts and electron microscopy. The virus was biologically purified from a single local lesion that developed on Chenopodium amaranticolor. The AMV infection was further confirmed using an AMV coat protein-specific primer RT-PCR. We further evaluated the antiviral potential of chitosan nanoparticles (CS-NPs) and chitosan silver nanocomposites (CS-Ag NC) in different concentrations against AMV infections in pepper plants. All tested concentrations of CS-NPs and CS-Ag NC induced the inhibition of AMV systemically infected pepper plants when applied 24 h after virus inoculation. The foliar application of 400 ppm CS-NPs or 200 ppm CS-Ag NC produced the highest AMV inhibitory effect (90 and 91%) when applied 24 h after virus inoculation. Treatment with CS-NPs and CS-Ag NC considerably increased the phenol, proline and capsaicin contents compared to the infected plants. Moreover, the agronomic metrics (plant height, fresh and dry pod weights and number of pods per plant) were also significantly improved. According to our results, the potential applications of CS-NPs and CS-Ag NC may provide an effective therapeutic measure for better AMV and other related plant virus management.

Nanotechnology in Food and Plant Science: Challenges and Future Prospects

Globally, food safety and security are receiving a lot of attention to ensure a steady supply of nutrient-rich and safe food. Nanotechnology is used in a wide range of technical processes, including the development of new materials and the enhancement of food safety and security. Nanomaterials are used to improve the protective effects of food and help detect microbial contamination, hazardous chemicals, and pesticides. Nanosensors are used to detect pathogens and allergens in food. Food processing is enhanced further by nanocapsulation, which allows for the delivery of bioactive compounds, increases food bioavailability, and extends food shelf life. Various forms of nanomaterials have been developed to improve food safety and enhance agricultural productivity, including nanometals, nanorods, nanofilms, nanotubes, nanofibers, nanolayers, and nanosheets. Such materials are used for developing nanofertilizers, nanopesticides, and nanomaterials to induce plant growth, genome modification, and transgene expression in plants. Nanomaterials have antimicrobial properties, promote plants' innate immunity, and act as delivery agents for active ingredients. Nanocomposites offer good acid-resistance capabilities, effective recyclability, significant thermostability, and enhanced storage stability. Nanomaterials have been extensively used for the targeted delivery and release of genes and proteins into plant cells. In this review article, we discuss the role of nanotechnology in food safety and security. Furthermore, we include a partial literature survey on the use of nanotechnology in food packaging, food safety, food preservation using smart nanocarriers, the detection of food-borne pathogens and allergens using nanosensors, and crop growth and yield improvement; however, extensive research on nanotechnology is warranted.

Antiviral Activity of Biosynthesized Silver Nanoparticles from Pomegranate (Punica granatum L.) Peel Extract against Tobacco Mosaic Virus

Tobacco mosaic virus (TMV) is a major pathogen affecting tomato plants worldwide. The efficacy of silver nanoparticles (Ag-NPs) mediated by Punica granatum biowaste peel extract in mitigating the negative impact of TMV infection on tomato growth and oxidative stress was investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Visible (UV-Vis) spectrophotometer, X-ray Diffraction (XRD), dynamic light scattering (DLS), zeta potential, energy-dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectra (FTIR). Results of SEM analysis of green Ag-NPs revealed the presence of condensed spherical or round NPs with diameters ranging between 61 and 97 nm. TEM confirmed the SEM results and showed round-shaped Ag-NPs with an average size of 33.37 ± 12.7 nm. The elemental analysis (EDX) of prepared Ag-NPs revealed the presence of elemental Ag as a major peak (64.43%) at 3-3.5 KeV. The FTIR revealed several functional groups on the prepared Ag-NPs, for which three treatment strategies for Ag-NP applications were evaluated in the greenhouse study and compared to inoculated TMV and control plants: pre-infection treatment (TB), post-infection treatment (TA), and dual treatment (TD). The results showed that the TD strategy is the most effective in improving tomato growth and reducing viral replication, whereas all Ag-NP treatments (TB, TA, and TD) were found to significantly increase expression of the pathogenesis-related (PR) genes PR-1 and PR-2, as well as polyphenolic compounds, HQT, and C4H genes compared to control plants. In contrast, the flavonoid content of tomato plants was not affected by the viral infection, while the phenolic content was significantly reduced in the TMV group. Furthermore, TMV infection led to a significant increase in oxidative stress markers MDA and H₂O₂, as well as a reduction in the enzymatic activity of the antioxidants PPO, SOD, and POX. Our results clearly showed that the application of Ag-NPs on TMV-infected plants reduces virus accumulation, delays viral replication in all treatments, and greatly enhances the expression of the CHS gene involved in flavonoid biosynthesis. Overall, these findings suggest that treatment with Ag-NPs may be an effective strategy to mitigate the negative impact of TMV infection on tomato plants.

Chitosan/silica: A hybrid formulation to mitigate phytopathogens

Long-term and indiscriminate use of synthetic pesticides to mitigate plant pathogens have created serious issues of water health, soil contamination, non-target organisms, resistant species, and unpredictable environmental and human health hazards. These constraints have forced scientists to develop alternative plant disease management strategies to reduce synthetic chemical' dependency. During the last 20 years, biological agents and resistance elicitors have been the most important used alternatives. Silica-based materials/chitosan with a dual mode of action have been proposed as promising alternatives to prevent plant diseases through direct and indirect mechanisms. Moreover, the combined application of nano-silica and chitosan, due to their controllable morphology, high loading capacity, low toxicity, and efficient encapsulation, act as suitable carriers for biological agents, pesticides, and essential oils, making them proper candidates for mitigation of phytopathogens. Based on this potential, this literature study reviewed the silica and chitosan properties and their function in the plant. It also assessed their role in the fighting against soil and aerial phytopathogens, directly and indirectly, as novel hybrid formulations in future managing platforms.

A Review of Sustainable Use of Biogenic Nanoscale Agro-Materials to Enhance Stress Tolerance and Nutritional Value of Plants

Climate change is more likely to have a detrimental effect on the world's productive assets. Several undesirable conditions and practices, including extreme temperature, drought, and uncontrolled use of agrochemicals, result in stresses that strain agriculture. In addition, nutritional inadequacies in food crops are wreaking havoc on human health, especially in rural regions of less developed countries. This could be because plants are unable to absorb the nutrients in conventional fertilizers, or these fertilizers have an inappropriate or unbalanced nutrient composition. Chemical fertilizers have been used for centuries and have considerably increased crop yields. However, they also disrupt soil quality and structure, eventually impacting the entire ecosystem. To address the situation, it is necessary to develop advanced materials that can release nutrients to targeted points in the plant-soil environment or appropriate receptors on the leaf in the case of foliar applications. Recently, nanotechnology-based interventions have been strongly encouraged to meet the world's growing food demand and to promote food security in an environmentally friendly manner. Biological approaches for the synthesis of nanoscale agro-materials have become a promising area of research, with a wide range of product types such as nanopesticides, nanoinsecticides, nanoherbicides, nanobactericides/fungicides, bio-conjugated nanocomplexes, and nanoemulsions emerging therefrom. These materials are more sustainable and target-oriented than conventional agrochemicals. In this paper, we reviewed the literature on major abiotic and biotic stresses that are detrimental to plant growth and productivity. We comprehensively discussed the different forms of nanoscale agro-materials and provided an overview of biological approaches in nano-enabled strategies that can efficiently alleviate plant biotic and abiotic stresses while potentially enhancing the nutritional values of plants.

Evaluation of the Impacts of Potassium Bicarbonate, Moringa oleifera Seed Extract, and Bacillus subtilis on Sugar Beet Powdery Mildew

Powdery mildew disease, caused by Erysiphe betae, is one of the most threatening diseases on sugar beet plants worldwide. It causes a great loss in the root yield, sugar percentage, and quality of produced sugar. In the current study, we aimed to evaluate the susceptibility of 25 sugar beet cultivars to infection with powdery mildew disease under Egyptian conditions. Moreover, we evaluated the impacts of three eco-friendly materials, including potassium bicarbonate (KHCO₃; at 5 and 10 g L^-1), Moringa oleifera seed extract (25 and 50 g L^-1), and the biocontrol agent, Bacillus subtilis (10⁸ cell suspension) against E. betae in two successive seasons 2020 and 2021. Our findings showed that there were significant differences between these 25 cultivars in their susceptibility to the disease under study. Using the detached leaves technique in vitro, B. subtilis showed strong antifungal activity against E. betae. Moreover, both concentrations of KHCO₃ and moringa seed extract significantly reduced the disease severity. Under field conditions, tested treatments significantly reduced the severity of powdery mildew disease and prevented E. betae from producing its conidiophores and conidia. Scanning electron microscope examination of treated leaves demonstrated the presence of the decomposition of fungal hyphae, conidiophores, conidia, and the occurrence of plasmolysis to fungal cells and spores on the surface of the leaves. Furthermore, these treatments greatly improved the percent of sucrose and soluble solids content, as well as the enzymatic activity of peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase. It is noteworthy that treatment with moringa seed extract gave the best results, followed by potassium bicarbonate, then B. subtilis cell suspension. Generally, it is recommended to use the substances used in this research to combat powdery mildew to minimize or prevent the use of chemical fungicides harmful to public health and the environment.

Ocimum basilicum-Mediated Synthesis of Silver Nanoparticles Induces Innate Immune Responses against Cucumber Mosaic Virus in Squash

Cucumber mosaic virus (CMV) causes a significant threat to crop output sustainability and human nutrition worldwide, since it is one of the most prevalent plant viruses infecting most kinds of plants. Nowadays, different types of nanomaterials are applied as a control agent against different phytopathogens. However, their effects against viral infections are still limited. In the current study, the antiviral activities of the biosynthesized silver nanoparticles (Ag-NPs) mediated by aqueous extract of Ocimum basilicum against cucumber mosaic virus in squash (Cucurbita pepo L.) were investigated. The prepared Ag-NPs were characterized using scanning electron microscopy (SEM), dynamic light scattering (DLS), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and zeta potential distribution techniques. DLS, SEM, and TEM analyses showed that the Ag-NPs were spherical, with sizes ranging from 26.3 to 83 nm with an average particle size of about 32.6 nm. FTIR identified different functional groups responsible for the capping and stability of Ag-NPs. The zeta potential was reported as being -11.1 mV. Under greenhouse conditions, foliar sprays of Ag-NPs (100 µg/mL) promoted growth, delayed disease symptom development, and significantly reduced CMV accumulation levels of treated plants compared to non-treated plants. Treatment with Ag-NPs 24 h before or after CMV infection reduced CMV accumulation levels by 92% and 86%, respectively. There was also a significant increase in total soluble carbohydrates, free radical scavenging activity, antioxidant enzymes (PPO, SOD, and POX), as well as total phenolic and flavonoid content. Furthermore, systemic resistance was induced by significantly increasing the expression levels of pathogenesis-related genes (PR-1 and PR-5) and polyphenolic pathway genes (HCT and CHI). These findings suggest that Ag-NPs produced by O. basilicum could be used as an elicitor agent and as a control agent in the induction and management of plant viral infections.

Defense Responses and Metabolic Changes Involving Phenylpropanoid Pathway and PR Genes in Squash (Cucurbita pepo L.) following Cucumber mosaic virus Infection

The current study focuses on the effects of Cucumber mosaic virus (CMV) infection on phytochemical changes and pathogenesis- and phenylpropanoid pathway-associated gene activities in squash (Cucurbita pepo L.) plants during a time course of 2 to 12 days post inoculation (dpi). The identity of the CMV isolate was confirmed by DAS-ELISA, TEM, and coat protein gene sequence. The CMV infection initially boosts and then suppresses transcript levels of the defense-related genes PR-1, PR-2, PAL, HQT, and CHS during the investigated time course compared to controls. The expression profile during the time-course study indicated that early, transient induction of PR-1 occurs during CMV infection, while CMV induced the expression of PR-2 in systemically infected squash tissues at all time points and suppressed the expression of PAL and HQT at 8-12 dpi. CHS transcript levels fluctuated between up- and down-regulation, but by 12 dpi, CHS expression reached its peak. The HPLC and GC–MS analyses of CMV-infected squash extracts revealed that different phenolic, flavonoid, and fatty acid compounds could be induced or suppressed upon CMV infection. In particular, CMV could suppress the synthesis of most phenolic compounds, specifically chlorogenic acid, possibly leading to the virus’s rapid spread.

Foliar Applications of Bacillus subtilis HA1 Culture Filtrate Enhance Tomato Growth and Induce Systemic Resistance against Tobacco mosaic virus Infection

The application of microbial products as natural biocontrol agents for inducing systemic resistance against plant viral infections represents a promising strategy for sustainable and eco-friendly agricultural applications. Under greenhouse conditions, the efficacy of the culture filtrate of Bacillus subtilis strain HA1 (Acc# OM286889) for protecting tomato plants from Tobacco mosaic virus (TMV) infection was assessed. The results showed that the dual foliar application of this culture filtrate (HA1-CF) 24 h before and 24 h after TMV inoculation was the most effective treatment for enhancing tomato plant development, with substantial improvements in shoot and root parameters. Furthermore, compared to non-treated plants, HA1-CF-treated tomato had a significant increase in total phenolic and flavonoid contents of up to 27% and 50%, respectively. In addition, a considerable increase in the activities of reactive oxygen species scavenging enzymes (PPO, SOD, and POX) and a significant decrease in non-enzymatic oxidative stress markers (H2O2 and MDA) were reported. In comparison to untreated control plants, all HA1-CF-treated plants showed a significant reduction in TMV accumulation in systemically infected tomato leaves, up to a 91% reduction at 15 dpi. The qRT-PCR results confirmed that HA1-CF stimulated the transcription of several defense-related tomato genes (PR-1, PAL, CHS, and HQT), pointing to their potential role in induced resistance against TMV. GC–MS analysis showed that phenol, 2,4-bis (1,1-dimethylethyl)-, Pyrrolo [1,2-a] pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl)- and eicosane are the primary ingredient compounds in the HA1-CF ethyl acetate extract, suggesting that these molecules take part in stimulating induced systemic resistance in tomato plants. Our results imply that HA1-CF is a potential resistance inducer to control plant viral infections, a plant growth promoter, and a source of bioactive compounds for sustainable disease management.

Trichoderma hamatum Strain Th23 Promotes Tomato Growth and Induces Systemic Resistance against Tobacco Mosaic Virus

Trichoderma hamatum strain Th23, isolated from tomato roots, was molecularly identified using phylogenetic analysis based on ITS, tef1, and rpb2 gene sequences and evaluated for its efficiency in suppressing tobacco mosaic virus (TMV) infection for the first time. Under greenhouse conditions, the application of Th23 promoted tomato growth with significant increases in shoot and root parameters as well as improved total chlorophyll content. Compared to the nontreated tomato plants, the soil pretreatment of tomato plants 48 h before TMV inoculation produced a significant reduction in the TMV accumulation level by 84.69% and enhanced different growth parameters. In contrast, TMV had a deleterious impact on fresh and dry matter accumulation and inhibited photosynthetic capacity. Furthermore, the protective activity of Th23 was associated with a significant increase in reactive oxygen species scavenging enzymes (PPO, CAT, and SOD) as well as decreased nonenzymatic oxidative stress markers (H₂O₂ and MDA) compared to the TMV treatment at 15 days post-viral inoculation (dpi). In addition, considerable increases in the transcriptional levels of polyphenolic genes (HQT and CHS) and pathogenesis-related proteins (PR-1 and PR-7) were shown to induce systemic resistance against TMV. Consequently, the ability of T. hamatum strain Th23 to promote plant growth, induce systemic resistance, and boost innate immunity against TMV infestation supported the incorporation of Th23 as a potential biocontrol agent for managing plant viral infections. To the best of our knowledge, this is the first report of the antiviral activity of T. hamatum against plant viral infection.