Tobacco Necrosis Virus Research Articles

The Nature and Origin of Plant Viruses with an Incursion into Virus Nomenclature

Eversince, the chemical nature of not only the anisometric tobacco mosaic virus (TMV) but also the crystalline viruses like bushy stunt of tomato, tobacco necrosis virus, turnip yellow mosaic virus and others have been characterized, sap transmissible viruses have been shown to be good antigens and that their antisera had group specificity aiding identification. Whilst symptomatology alone was found unreliable and of insufficient means for diagnosis and classification of viruses, serology, chemical and physical structure of viruses and the modes of transmission have played an important role in virus nomenclature. However, it is premature to think of orthodox binomial and trinomial nomenclature as practised in fungal classification playing a role in virus terminology, Anisometric and crystalline viruses are comparatively simple chemical entities (as compared with animal viruses) and are essentially nucleoproteins where the RNA (ribonucleic acid) core has a shell of protein in a helical pattern serving as a protective coating. The infectivity of the nucleic acid alone (which is hardly 6% of the nucleoproteiri) has been proved beyond doubt whereas, the protein (which is the bulk of the virus) does not count for infectivity but plays an important role in serological reactions and consequently is of immense value in grouping viruses. Nevertheless, size, shapes and structure of viruses are of considerable significance as a tool in virus classification of rodshaped particles. Spherical virus particles, however, have not lent themselves to this approach. A somewhat similar approach to classification has been made by using specific vector-virus relationships.In the speculative field of origin of viruses, the free gene or plasmagene theory of Darlington seems to find little support at present. Nonetheless, a biochemical approach is still valid and as all the ribonucleic acid (RNA) in the TMV appears to be present in a single polynucleotide chain, a break in this chain has to be transmitted intact to the recipient cell to enable reduplication. That the RNA may be replicated in the cells is, therefore, not to be regarded as a shortlived messenger carrying genetic information from nuclear deoxyribonucleic acid (DNA) to protein. Stretching this argument one could conceive of a further step to the self-perpetuating RNA molecule capable of directing protein synthetic mechanisms in recipient cells to specific products.

First report of Tobacco necrosis virus D infecting tomato in Greece

First report of <i>Tobacco necrosis virus D</i> infecting tomato in Greece

Molecular characterization and genetic analysis of Orthotospovirus tomatomaculae (tomato spotted wilt virus) and cucumber mosaic virus infecting tomato and pepper in Türkiye

Many viral diseases threaten the sustainable production of tomato (Solanum lycopersicum) and pepper (Capsicum annuum), which are among the most produced vegetables in the world and Türkiye. Eskişehir province of Türkiye produces a significant amount of vegetables both in the greenhouse and in the open-field. However, there have been no previous comprehensive study on the presence of viruses in tomato and pepper fields. In this study, 123 of 170 samples (72.4%) collected from tomato and pepper fields in Eskişehir in 2019 were infected with different viruses listed. While Orthotospovirus tomatomaculae (tomato spotted wilt virus, TSWV), cucumber mosaic virus (CMV), potato virus Y (PVY), tomato mosaic virus (ToMV), tobacco mosaic virus (TMV) viruses were detected by DAS-ELISA, pepino mosaic virus (PepMV), tomato chlorosis virus (ToCV) and tobacco necrosis virus (TNV) viruses could not be detected in both host plants. To molecularly characterize the selected isolates, the complete nucleocapsid (N) gene region specific to TSWV and a partial capsid protein (CP) gene region specific to CMV were amplified via RT-PCR, followed by sequencing. Phylogenetic trees were constructed with NCBI GenBank isolates and newly sequenced isolates. Genetic structure-related analyses such as genetic diversity, genetic differentiation, gene flow, neutrality tests, selection pressure, and recombination were performed on populations. In the phylogenetic tree of the TSWV N gene, the isolates are divided into three clades of geographical origin. Genetic structure analyses revealed that TSWV populations exhibited genetic diversity. In the phylogenetic tree of the CMV CP gene, the isolates are divided into known subgroups. The analyses indicate the presence of high genetic diversity and suggest that Subgroup IB, one of the clades, may contain subgroups within itself. In addition, there are indications for the existence of different CMV subgroups in Türkiye. Although different approaches were used for both the TSWV N gene and CMV CP gene, no recombination event could be detected. This study, marking the initial identification of viruses in tomatoes and peppers within the Eskişehir region, is believed to hold substantial potential for advancing future research endeavors and enhancing disease management not only within Türkiye but also globally.

Enhanced Resistance to Viruses in Nicotiana edwardsonii 'Columbia' Is Dependent on Salicylic Acid, Correlates with High Glutathione Levels, and Extends to Plant-Pathogenic Bacteria and Abiotic Stress.

Our earlier research showed that an interspecific tobacco hybrid (Nicotiana edwardsonii 'Columbia' [NEC]) displays elevated levels of salicylic acid (SA) and enhanced resistance to localized necrotic symptoms (hypersensitive response [HR]) caused by tobacco mosaic virus (TMV) and tobacco necrosis virus (TNV), as compared with another interspecific hybrid (Nicotiana edwardsonii [NE]) derived from the same parents. In the present study, we investigated whether symptomatic resistance in NEC is indeed associated with the inhibition of TMV and TNV and whether SA plays a role in this process. We demonstrated that enhanced viral resistance in NEC is manifested as both milder local necrotic (HR) symptoms and reduced levels of TMV and TNV. The presence of an adequate amount of SA contributes to the enhanced defense response of NEC to TMV and TNV, as the absence of SA resulted in seriously impaired viral resistance. Elevated levels of subcellular tripeptide glutathione (GSH) in NEC plants in response to viral infection suggest that in addition to SA, GSH may also contribute to the elevated viral resistance of NEC. Furthermore, we found that NEC displays an enhanced resistance not only to viral pathogens but also to bacterial infections and abiotic oxidative stress induced by paraquat treatments. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Transiently Induce RNA Silencing in Plants Using a Tobacco Necrosis Virus A (TNV-A)-Based dsRNA Production System.

Transgenic expression of hairpin RNA or artificial microRNA is widely used for genetic studies in plant science. However, induction of RNA silencing by transgenic method may have aproblem when studying essential genes. Here, we provide an in planta transient double-stranded RNA (dsRNA) producing systemusing a tobacco necrosis virus A (TNV-A)-based replicon for efficiently inducing RNA silencing in plants. In this system, the target sequence is placed between the cauliflower mosaic virus 35S promoter and the 3'-terminal part of viral genomic RNA, while the C-terminal part of TNV-A RNA-dependent RNA polymerase (p82C) is expressed by a different promoter. The endogenous RNA polymerase-synthesized target sequence is recruited by p82C to produce dsRNA to induce RNA silencing.

First Report of Olive Mild Mosaic Virus in Imported Tulips (Tulipa gesneriana) in Korea.

Tulip cultivation in Korea primarily uses imported bulbs due to the absence of domestic production. To ensure safety and sustainability, Korean authorities have implemented strict phytosanitary measures for five viruses: arabis mosaic virus, tobacco necrosis virus, tobacco ringspot virus, tomato black ring virus, and tomato bushy stunt virus. In April 2021, 86 tulip plants presented symptoms such as chlorotic mottle, mosaic, streak, stripe, yellowing of the leaves, and color breaking on flowers. These samples were collected to investigate the incidence of viruses in four Korean provinces (Gangwon, Gyeongbuk, Gyeongnam, and Chungnam). The leaves and petals from each individual sample (10 mg each) were pooled and ground using liquid nitrogen. Total RNA was extracted using a Maxwell® 16 LEV Plant RNA Kit (Promega, Madison, USA). A cDNA library was constructed using TruSeq Standard Total RNA with Ribo - Zero (Illumina, San Diego, USA) and sequenced on an Illumina NovaSeq 6000 platform (Macrogen, Seoul, Korea) with 100-bp paired-end reads. Trinity software identified tulip breaking virus (TBV), tulip virus X (TVX), and lily symptomless virus (LSV), which are known to occur in Korea (Bak et al. 2023) by de novo assembly of 628 million reads into 498,795 contigs. The contigs were annotated as previously described (Bak et al. 2022). Moreover, a contig (ON758350) related to olive mild mosaic virus (OMMV; genus Alphanecrovirus, family Tombusviridae) was identified through BLASTn analysis. This contig had a 99.27% nucleotide (nt) identity to OMMV PPO-L190209 (KU641010), which was assembled from 201,346 reads and spanned 3,713 bp. To confirm the presence of OMMV, a primer pair (5'-GAATGTCTGGCGTTAAGCG-3'/5'-GTGTCCTGCGCATCATACAC-3') was designed to amplify a 797-bp fragment of the coat protein gene. In RT-PCR, 31.4% (27/86) of samples were positive for OMMV and coinfected with TBV or TBV+LSV. Coinfection with TBV led to chlorotic mottling and stripes, whereas triple coinfection with TBV+LSV produced distinct yellow streaks and mosaic within the lesion boundaries. In contrast, solely TBV infection did not produce such symptoms. The samples infected with OMMV were exclusively collected from Gangwon and Gyeongnam. In each province, an RT-PCR amplicon was cloned, and subsequently sequenced (Bioneer, Daejeon, Korea). The obtained sequences were named CC (OM243091) and GS (OM243092), and they shared 98.6% and 98.9% identity with PPO-L190209 (KU641010), respectively. A bioassay was conducted using a leaf infected with OMMV CC and TBV to inoculate 13 indicator species in triplicate, including Capsicum annuum, Chenopodium amaranticolor, C. quinoa, Cucumis sativus, Nicotiana benthamiana, N. clevelandii, N. glutinosa, N. occidentalis, N. rustica, N. tabacum, Solanum lycopersicum, Tetragonia tetragonioides, and Tulipa gesneriana. The RT-PCR revealed positivity only for OMMV in the upper leaves of N. clevelandii, while all other species were negative with no symptoms. To our knowledge, this is the first report of OMMV occurring in tulips grown from imported bulbs in Korea, with no other known natural hosts such as olive tree (Cardoso et al. 2004), spinach (Gratsia et al. 2012), and corn salad (Verdin et al. 2018). The Korean OMMV isolates exhibited a high nt identity with the foreign isolate, and the samples were collected from farms that rely entirely on bulb imports for cultivation. These suggest that the outbreak of OMMV was likely caused by imported bulbs.

Priming crop plants with rosemary (Salvia rosmarinus Spenn, syn Rosmarinus officinalis L.) extract triggers protective defense response against pathogens

Plant bioactive compounds provide novel straightforward approaches to control plant diseases. Rosemary (Salvia rosmarinus)-derived extracts carry many prominent pharmacological activities, including antimicrobial and antioxidant, mainly due to its phenolic compounds, rosmarinic acid (RA), carnosic acid and carnosol. However, the effects of these extracts on plant diseases are still unknown, which constrains its potential application as bioprotectant in the agricultural production. In this study we demonstrate the antiviral effect of the aqueous rosemary extract (ARE) against tobacco necrosis virus strain A (TNVA) in ARE-treated tobacco (Nicotiana tabacum) plants. Our results show that ARE-treatment enhances plant defense response, contributing to reduce virus replication and systemic movement in tobacco plants. RA, the main phenolic compound detected in this extract, is one of the main inducers of TNVA control. The ARE-induced protection in TNVA-infected plants was characterized by the expression of H2O2 scavengers and defense-related genes, involving salicylic acid- and jasmonic acid-regulated pathways. Furthermore, treatment with ARE in lemon (Citrus limon) and soybean (Glycine max) leaves protects the plants against Xanthomonas citri subsp. citri and Diaporthe phaseolorum var. meridionalis, respectively. Additionally, ARE treatment also promotes growth and development, suggesting a biostimulant activity in soybean. These results open the way for the potential use of ARE as a bioprotective agent in disease management.

PM 7/153 (1) Mechanical inoculation of test plants

PM 7/153 (1) Mechanical inoculation of test plants

PM 4/17 (3) Certification scheme for olive trees and rootstocks

<scp>PM</scp> 4/17 (3) Certification scheme for olive trees and rootstocks

Tobacco necrosis virus (augusta disease of tulip)

This datasheet on Tobacco necrosis virus covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Vectors &amp; Intermediate Hosts, Diagnosis, Biology &amp; Ecology, Seedborne Aspects, Impacts, Prevention/Control, Further Information.

Preliminary Study of Viruses Infecting Strawberry (Fragaria spp.) in the Midsouthern United States

Strawberry is an important economic crop in the midsouthern United States; however, limited information is known about the viruses present in strawberry fields in Arkansas, Missouri, Oklahoma, and Texas. The purpose of this study was to determine the presence of particular viruses infecting strawberry crops in these four states. A total of 816 strawberry leaf samples were randomly collected from growers’ fields during the 2014 and 2016 growing seasons and tested by dot-immunobinding assay against antisera of eight available viruses: apple mosaic virus (ApMV), arabis mosaic virus (ArMV), raspberry bushy dwarf virus (RBDV), raspberry ringspot virus, strawberry mild yellow edge virus (SMYEV), tobacco necrosis virus, tomato black ring virus, and tomato ringspot virus (ToRSV). Of the eight viruses, ApMV, RBDV, and SMYEV had the highest infection rates in 2014, whereas ApMV, ArMV, ToRSV and SMYEV were the most prevalent viruses in 2016. Mixed infection of more than one virus was very common in samples collected from all four states. Our preliminary results showed that the distribution of virus relative frequencies differed significantly among seven sample locations across the states within a sample year, but we could not show statistical differences among the years based on our sample sizes. Mixed infections in strawberries were higher than expected in 2014 and lower than expected in 2016 based on viruses being independent infections. Overall, the occurrence of the viruses in strawberry crops could have important potential impacts for strawberry production in the midsouthern states.

The Structural Characterization and Antipathogenic Activities of Quinoin, a Type 1 Ribosome-Inactivating Protein from Quinoa Seeds.

Quinoin is a type 1 ribosome-inactivating protein (RIP) we previously isolated from the seeds of pseudocereal quinoa (Chenopodium quinoa) and is known as a functional food for its beneficial effects on human health. As the presence of RIPs in edible plants could be potentially risky, here we further characterised biochemically the protein (complete amino acid sequence, homologies/differences with other RIPs and three-dimensional homology modeling) and explored its possible defensive role against pathogens. Quinoin consists of 254 amino acid residues, without cysteinyl residues. As demonstrated by similarities and homology modeling, quinoin preserves the amino acid residues of the active site (Tyr75, Tyr122, Glu177, Arg180, Phe181 and Trp206; quinoin numbering) and the RIP-fold characteristic of RIPs. The polypeptide chain of quinoin contains two N-glycosylation sites at Asn115 and Asp231, the second of which appears to be linked to sugars. Moreover, by comparative MALDI-TOF tryptic peptide mapping, two differently glycosylated forms of quinoin, named pre-quinoin-1 and pre-quinoin-2 (~0.11 mg/100 g and ~0.85 mg/100 g of seeds, respectively) were characterised. Finally, quinoin possesses: (i) strong antiviral activity, both in vitro and in vivo towards Tobacco Necrosis Virus (TNV); (ii) a growth inhibition effect on the bacterial pathogens of plants; and (iii) a slight antifungal effect against two Cryphonectria parasitica strains.

Three-dimensional reconstruction and comparison of vacuolar membranes in response to viral infection.

The vacuole is a unique plant organelle that plays an important role in maintaining cellular homeostasis under various environmental stress conditions. However, the effects of biotic stress on vacuole structure has not been examined using three-dimensional (3D) visualization. Here, we performed 3D electron tomography to compare the ultrastructural changes in the vacuole during infection with different viruses. The 3D models revealed that vacuoles are remodeled in cells infected with cucumber mosaic virus (CMV) or tobacco necrosis virus A Chinese isolate (TNV-AC ), resulting in the formation of spherules at the periphery of the vacuole. These spherules contain neck-like channels that connect their interior with the cytosol. Confocal microscopy of CMV replication proteins 1a and 2a and TNV-AC auxiliary replication protein p23 showed that all of these proteins localize to the tonoplast. Electron microscopy revealed that the expression of these replication proteins alone is sufficient to induce spherule formation on the tonoplast, suggesting that these proteins play prominent roles in inducing vacuolar membrane remodeling. This is the first report of the 3D structures of viral replication factories built on the tonoplasts. These findings contribute to our understanding of vacuole biogenesis under normal conditions and during assembly of plant (+) RNA virus replication complexes.

Tobacco Necrosis Virus-AC Single Coat Protein Amino Acid Substitutions Determine Host-Specific Systemic Infections of Nicotiana benthamiana and Soybean.

Plant viruses often infect several distinct host species. Sometimes, viruses can systemically infect a specific host whereas, in other cases, only local infections occur in other species. How viral and host factors interact to determine systemic infections among different hosts is largely unknown, particularly for icosahedral positive-stranded RNA viruses. The Tobacco necrosis virus-A Chinese isolate belongs to the genus Alphanecrovirus in the family Tombusviridae. In this study, we investigated variations in systemic infections of tobacco necrosis virus-AC (TNV-AC) in Nicotiana benthamiana and Glycine max (soybean) by alanine-scanning mutagenesis of the viral coat protein (CP), which is essential for systemic movement of TNV-AC. We found that three amino acids, R169, K177, and Q233, are key residues that mediate varying degrees of systemic infections of N. benthamiana and soybean. Further analysis revealed that variations in systemic trafficking of TNV-AC CP mutants in N. benthamiana and soybean are associated with virion assembly and stability. The CP amino acids K177 and Q233 are highly conserved among all TNV-A isolates and are replaced by Q and K in the TNV-D isolates. We demonstrated that systemic infectivity of either TNV-AC K177A and Q233A or K177Q and Q233K mutants are correlated with the binding affinity of the mutated CPs to the host-specific Hsc70-2 protein. These results expand our understanding of host-dependent long-distance movement of icosahedral viruses in plants.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Antiviral Activity of PD-L1 and PD-L4, Type 1 Ribosome Inactivating Proteins from Leaves of Phytolacca dioica L. in the Pathosystem Phaseolus vulgaris-Tobacco Necrosis Virus (TNV).

Using the pathosystem Phaseolus vulgaris–tobacco necrosis virus (TNV), we demonstrated that PD-L1 and PD-L4, type-1 ribosome inactivating proteins (RIPs) from leaves of Phytolacca dioica L., possess a strong antiviral activity. This activity was exerted both when the RIPs and the virus were inoculated together in the same leaf and when they were inoculated or applied separately in the adaxial and abaxial leaf surfaces. This suggests that virus inhibition would mainly occur inside plant cells at the onset of infection. Histochemical studies showed that both PD-L1 and PD-L4 were not able to induce oxidative burst and cell death in treated leaves, which were instead elicited by inoculation of the virus alone. Furthermore, when RIPs and TNV were inoculated together, no sign of H2O2 deposits and cell death were detectable, indicating that the virus could have been inactivated in a very early stage of infection, before the elicitation of a hypersensitivity reaction. In conclusion, the strong antiviral activity is likely exerted inside host cells as soon the virus disassembles to start translation of the viral genome. This activity is likely directed towards both viral and ribosomal RNA, explaining the almost complete abolition of infection when virus and RIP enter together into the cells.

Investigation of Novel RNA Elements in the 3'UTR of Tobacco Necrosis Virus-D.

RNA elements in the untranslated regions of plus-strand RNA viruses can control a variety of viral processes including translation, replication, packaging, and subgenomic mRNA production. The 3′ untranslated region (3′UTR) of Tobacco necrosis virus strain D (TNV-D; genus Betanecrovirus, family Tombusviridae) contains several well studied regulatory RNA elements. Here, we explore a previously unexamined region of the viral 3′UTR, the sequence located upstream of the 3′-cap independent translation enhancer (3′CITE). Our results indicate that (i) a long-range RNA–RNA interaction between an internal RNA element and the 3′UTR facilitates translational readthrough, and may also promote viral RNA synthesis; (ii) a conserved RNA hairpin, SLX, is required for efficient genome accumulation; and (iii) an adenine-rich region upstream of the 3′CITE is dispensable, but can modulate genome accumulation. These findings identified novel regulatory RNA elements in the 3′UTR of the TNV-D genome that are important for virus survival.

RNAseq Analysis of Rhizomania-Infected Sugar Beet Provides the First Genome Sequence of Beet Necrotic Yellow Vein Virus from the USA and Identifies a Novel Alphanecrovirus and Putative Satellite Viruses.

“Rhizomania” of sugar beet is a soilborne disease complex comprised of beet necrotic yellow vein virus (BNYVV) and its plasmodiophorid vector, Polymyxa betae. Although BNYVV is considered the causal agent of rhizomania, additional viruses frequently accompany BNYVV in diseased roots. In an effort to better understand the virus cohort present in sugar beet roots exhibiting rhizomania disease symptoms, five independent RNA samples prepared from diseased beet seedlings reared in a greenhouse or from field-grown adult sugar beet plants and enriched for virus particles were subjected to RNAseq. In all but a healthy control sample, the technique was successful at identifying BNYVV and provided sequence reads of sufficient quantity and overlap to assemble > 98% of the published genome of the virus. Utilizing the derived consensus sequence of BNYVV, infectious RNA was produced from cDNA clones of RNAs 1 and 2. The approach also enabled the detection of beet soilborne mosaic virus (BSBMV), beet soilborne virus (BSBV), beet black scorch virus (BBSV), and beet virus Q (BVQ), with near-complete genome assembly afforded to BSBMV and BBSV. In one field sample, a novel virus sequence of 3682 nt was assembled with significant sequence similarity and open reading frame (ORF) organization to members within the subgenus Alphanecrovirus (genus Necrovirus; family Tombusviridae). Construction of a DNA clone based on this sequence led to the production of the novel RNA genome in vitro that was capable of inducing local lesion formation on leaves of Chenopodium quinoa. Additionally, two previously unreported satellite viruses were revealed in the study; one possessing weak similarity to satellite maize white line mosaic virus and a second possessing moderate similarity to satellite tobacco necrosis virus C. Taken together, the approach provides an efficient pipeline to characterize variation in the BNYVV genome and to document the presence of other viruses potentially associated with disease severity or the ability to overcome resistance genes used for sugar beet rhizomania disease management.

A Heterologous Viral Protein Scaffold for Chimeric Antigen Design: An Example PCV2 Virus Vaccine Candidate.

Recombinant vaccines have low-cost manufacturing, regulatory requirements, and reduced side effects compared to attenuated or inactivated vaccines. In the porcine industry, post-weaning multisystemic disease syndrome generates economic losses, characterized by progressive weight loss and weakness in piglets, and it is caused by porcine circovirus type 2 (PCV2). We designed a chimeric antigen (Qm1) to assemble the main exposed epitopes of the Cap-PCV2 protein on the capsid protein of the tobacco necrosis virus (TNV). This design was based on the Cap-N-terminal of an isolated PCV2 virus obtained in Chile. The virus was characterized, and the sequence was clustered within the PCV2 genotype b clade. This chimeric protein was expressed as inclusion bodies in both monomeric and multimeric forms, suggesting a high-molecular-weight aggregate formation. Pigs immunized with Qm1 elicited a strong and specific antibody response, which reduced the viral loads after the PCV2 challenge. In conclusion, the implemented design allowed for the generation of an effective vaccine candidate. Our proposal could be used to express the domains or fragments of antigenic proteins, whose structural complexity does not allow for low-cost production in Escherichia coli. Hence, other antigen domains could be integrated into the TNV backbone for suitable antigenicity and immunogenicity. This work represents new biotechnological strategies, with a reduction in the costs associated with vaccine development.

A minimal coarse-grained model for the low-frequency normal mode analysis of icosahedral viral capsids.

The main goal of this work is the design of a coarse-grained theoretical model of minimal resolution for the study of the physical properties of icosahedral virus capsids within the linear-response regime. In this model the capsid is represented as an interacting many-body system whose composing elements are capsid subunits (capsomers), which are treated as three-dimensional rigid bodies. The total interaction potential energy is written as a sum of pairwise capsomer-capsomer interactions. Based on previous work [Gomez Llorente et al., Soft Matter, 2014, 10, 3560], a minimal and complete anisotropic binary interaction that includes a full Hessian matrix of independent force constants is proposed. In this interaction model, capsomers have rotational symmetry around an axis of order n > 2. The full coarse-grained model is applied to analyse the low-frequency normal-mode spectrum of icosahedral T = 1 capsids. The model performance is evaluated by fitting its predicted spectrum to the full-atom results for the Satellite Tobacco Necrosis Virus (STNV) capsid [Dykeman and Sankey, Phys. Rev. Lett., 2008, 100, 028101]. Two capsomer choices that are compatible with the capsid icosahedral symmetry are checked, namely pentamers (n = 5) and trimers (n = 3). Both subunit types provide fair fits, from which the magnitude of the coarse-grained force constants for a real virus is obtained. The model is able to uncover latent instabilities whose analysis is fully consistent with the current knowledge about the STNV capsid, which does not self-assemble in the absence of RNA and is thermally unstable. The straightforward generalisability of the model beyond the linear regime and its completeness make it a promising tool to theoretically interpret many experimental data such as those provided by the atomic force microscopy or even to better understand processes far from equilibrium such as the capsid self-assembly.

Use of biocides for controlling viral diseases that attack common bean and cucumber plants

Abstract This study aimed at investigating the antiviral activities of biocides made of formulated essential oils. These were derived from five plant species: fennel, oregano, peppermint, thyme and ginger. The potencies of these preparations were tested against local infection with the Tobacco necrosis virus (TNV) on common bean (Phaseolus vulgaris L.) and against systemic infection with the Cucumber mosaic virus (CMV) on cucumber (Cucumis sativus L.). After the determination of the most effective concentration, the formulated biocides were tested in protective and curative manners (before and after virus inoculation) against the growth of plants. The obtained results showed that the peppermint-derived biocide had the greatest effect on reducing the infectivity of the TNV virus (100% growth inhibition at 4000 ppm), whereas the biocide from thyme was the most effective against the infectivity of the CMV virus, as it induced a complete growth inhibition at 3000 ppm. The results of the protective and curative experiments revealed that the formulated biocides exerted high protection and curative effects against the two viruses. The observations revealed that the biocides were able to enhance plant defences against viral infection, as indicated by the increased levels of total chlorophyll, protein and phenols. Moreover, the levels of the oxidative stress markers including peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) were improved compared to the control settings. In conclusion, the formulated biocides progressively present a favourable alternative to chemically synthesized pesticides in crop protection.