IntroductionThe Tobamovirus fructirugosum, tomato brown rugose fruit virus (ToBRFV) is a mechanically transmitted, seed- and soil-borne virus causing severe damage to tomato crops worldwide. Under monoculture conditions, infected residues enable ToBRFV to persist in soil, initiating infectious foci in newly planted seedlings. These plants are then exposed to foliar mechanical inoculations, facilitating disease spread. Management strategies include the use of ToBRFV-resistant germplasms.MethodsWe screened 52 wild and 45 cultivated tomato varieties for ToBRFV resistance using foliar inoculation, symptom scoring, and ELISA. Lines harboring the Tm-1 resistance gene were used to generate resistant rootstocks and scions, which were challenged with ToBRFV. Grafting combinations of resistant and susceptible plants were evaluated under controlled root and foliar inoculations, as well as in commercial field trials.ResultsScreening identified complete resistance in wild Solanum accessions and cultivated lines carrying Tm-1. Controlled experiments showed that susceptible rootstocks enabled infection of resistant scions following root inoculations, whereas resistant rootstocks limited soil-mediated infection of susceptible scions. In field trials, resistant rootstocks reduced early fruit symptoms. Combining resistant scions with resistant rootstocks (RS/RR) resulted in a 16.43% infection rate, compared to over 92% in susceptible controls.DiscussionResistant rootstocks act as a barrier against soil-mediated ToBRFV transmission and reduce economic losses by limiting fruit symptoms. However, they do not protect against direct foliar infection. Thus, combining Tm-1-based resistant scions with resistant rootstocks is essential for durable disease management.

IntroductionTomato brown rugose fruit virus (ToBRFV) is a rapidly spreading plant pathogen that threatens tomato cultivation worldwide, leading to economic losses. ToBRFV-A134T, a new isolate, induces a subset of plant responses characterized by unique severe shoestring-like and fern-like manifestations. We aimed to investigate the differential host response of Tm-22-resistant tomato plants toward ToBRFV-A134T versus the wildtype isolate (ToBRFV-WT) to understand the mechanisms underlying these distinct manifestations.MethodsWe performed symptomatology analysis to follow the temporal development of shoestring and fern-like symptoms in ToBRFV-A134T-infected tomato plants. Comparative transcriptomic analysis of RNA-seq data from three biological replicates per leaf manifestation, sampled at 38 days post-inoculation, was conducted to identify differentially expressed genes and enriched pathways. In parallel, ToBRFV-WT-infected tomato plants were treated with exogenous auxin to test whether auxin perturbation could recapitulate ToBRFV-A134T-associated symptoms.ResultsShoestring symptoms consistently preceded fern-like symptoms in ToBRFV-A134T-infected plants and progressed to a mixture of manifestations at late disease stages. ToBRFV-A134T-induced shoestring symptoms were associated with a distinct subset of auxin-responsive genes and enrichment of the MAP kinase pathway. Salicylic acid-mediated defense was suppressed in shoestring leaves but remained active in fern-like leaves, as indicated by downregulation versus upregulation of Pathogenesis related-1 (PR-1) genes, respectively. Despite equivalent ToBRFV accumulation across infected phenotypes, fern-like leaves showed a transcriptional profile highly similar to that of healthy, non-infected controls. Exogenous auxin treatments of ToBRFV-WT-infected plants increased the occurrence of shoestring symptoms and recapitulated the unique fern-like manifestations induced by ToBRFV-A134T.DiscussionThese findings indicate that distinct rewiring of auxin signaling, MAPK signaling, and salicylic acid-mediated defense is associated with divergent foliar manifestations of ToBRFV disease in Tm-22-resistant tomato plants. Auxin emerges as a key determinant of symptom identity, linking hormonal crosstalk to the contrasting shoestring and fern-like outcomes observed for the ToBRFV-A134T isolate.

Tomato brown rugose fruit virus (ToBRFV) is a seedborne, soilborne, mechanically transmitted tobamovirus infecting tomato plants worldwide. Tobamovirus-contaminated soil occurring after a growth cycle of infected crops constitutes a primary source of infection for newly planted seedlings, severely affecting crops under the common practice of monoculture farming. For our studies of interrelationships between ToBRFV-infected plants and virus preservation in soil, we have grown ToBRFV-inoculated wild tomato species for 5 months and analyzed ToBRFV preservation in soil after plant removal. Soil virion RNA subjected to a high-throughput sequencing analysis revealed the presence of a single isolate with 99.92% similarity to wildtype (WT) ToBRFV. The isolate recovered from the soil contained one nonsynonymous mutation at the movement protein resulting in A134T amino acid substitution. ToBRFV-A134T was stable in Tm-22-resistant tomato plants (e.g., cv. Ikram), and in coinoculation experiments with ToBRFV-WT, both isolates were present. The effect of ToBRFV-A134T on tomato plants was studied in comparison with ToBRFV-WT infections. Whereas ToBRFV-WT-infected plants showed mottling-mosaic leaves occasionally associated with shoestring-like symptoms, ToBRFV-A134T-infected plants' leaves showed severe shoestring-like symptoms and unique fern-like leaflets on shoestring-like leaf backbones. Analyses of genes involved in shoestring-like symptoms in Tm-22-resistant tomato plants by RT-qPCR revealed differential relative expression of RNA-dependent RNA polymerase 6b, Dicer-like 4, and Dicer-like 2b in ToBRFV-WT-infected Ikram plants compared with ToBRFV-A134T-infected plants. The results may indicate that different mechanisms are involved in the regulation of severe shoestring-like symptoms induced by ToBRFV-A134T compared with symptoms induced by ToBRFV-WT.

Background and aims Tobamoviruses are highly stable soil-borne pathogens posing a challenge to a monoculture practice. Biochemical and physical properties of tobamovirus virions were studied by analyses of tobacco mosaic virus (TMV). Little is known about tomato brown rugose fruit tobamovirus (ToBRFV) regarding longevity in soil and virion stability. Our aims were to determine ToBRFV longevity in naturally-contaminated soil and study virion stability in a range of acidic and alkaline conditions to promote new strategies for soil remediation.Methods ToBRFV longevity in naturally-contaminated soil was tested by collecting an earth pile after a growth-cycle of ToBRFV-infected tomato plants. The soil was sampled at different time points and root-truncated tomato seedlings were planted. Virion stability at a range of pH values was determined by testing virus infectivity on Nicotiana glutinosa ; by amplifying large genome segments using RT-PCR; and by transmission electron microscopy (TEM) visualization.Results ToBRFV-infectivity in naturally-contaminated soil was profoundly reduced by day 184 of pile-age and was abolished between 205-385 days of pile-age. Virion stability and genome integrity were preserved over the pH range of 2-10. At pH 1, ToBRFV-infectivity and efficiency of large genome segment amplifications were reduced. At pH values above 10, modified particle morphologies were visualized by TEM, and virus infectivity was abolished. Treatment of ToBRFV-contaminated soil with an alkaline chlorinated-trisodium phosphate solution profoundly reduced soil-mediated virus infection of root-truncated tomato seedlings.Conclusions pH values above 10, compromised ToBRFV particle morphology genome integrity and virus infectivity. Alkaline disinfectant enhanced soil remediation following natural ToBRFV contamination.### Competing Interest StatementThe authors have declared no competing interest.

High cannabidiol‐containing plants of Cannabis sativa (high‐CBD) growing in farms in Israel displayed foliar symptoms of interveinal chlorosis and yellowing, brittleness and occasionally necrosis. These symptoms, which were more apparent in older leaves, resembled those caused by the crinivirus lettuce chlorosis virus (LCV). However, this virus was not detected by reverse transcription (RT)‐PCR using specific primer sets. High‐throughput sequencing of viral RNA extracted from symptomatic leaves revealed the presence of cucurbit chlorotic yellows virus (CCYV), a crinivirus in the Closteroviridae family. The complete viral genome sequence was obtained using RT‐PCR followed by Sanger sequencing. The two CCYV RNA genomic segments shared 99.5%–99.85% nucleotide sequence identity with CCYV isolates from the GenBank. The virus was transmitted from symptomatic cannabis leaves to healthy plants of cannabis and Cucumis sativus ‘King Star’ (cucumber) by the whitefly Bemisia tabaci Middle Eastern Asia Minor 1 (MEAM1) species, causing disease symptoms identical to those of the donor plants. Cannabis‐CCYV was also transmitted between infected cucumber plants and cannabis seedlings of unknown genotype. Severe disease symptoms of yellowing and leaf‐edge necrosis were observed on high‐CBD and high Δ 9 ‐tetrahydrocannabinol‐containing (high‐THC) flowering cannabis plants and were associated with mixed infections of LCV and CCYV. To the best of our knowledge, this is the first report of CCYV infecting C . sativa plants.

Background and aims Tobamoviruses are highly stable soil-borne pathogens posing a challenge to a monoculture practice. Biochemical and physical properties of tobamovirus virions were studied by analyses of tobacco mosaic virus (TMV). Little is known about tomato brown rugose fruit tobamovirus (ToBRFV) regarding longevity in soil and virion stability. Our aims were to determine ToBRFV longevity in naturally-contaminated soil and study virion stability in a range of acidic and alkaline conditions to promote new strategies for soil remediation. Methods ToBRFV longevity in naturally-contaminated soil was tested by collecting an earth pile after a growth-cycle of ToBRFV-infected tomato plants. The soil was sampled at different time points and root-truncated tomato seedlings were planted. Virion stability at a range of pH values was determined by testing virus infectivity on Nicotiana glutinosa ; by amplifying large genome segments using RT-PCR; and by transmission electron microscopy (TEM) visualization. Results ToBRFV-infectivity in naturally-contaminated soil was profoundly reduced by day 184 of pile-age and was abolished between 205 and 385 days of pile-age. Virion stability and genome integrity were preserved over the pH range of 2-10. At pH 1, ToBRFV-infectivity and efficiency of large genome segment amplifications were reduced. At pH values above 10, modified particle morphologies were visualized by TEM, and virus infectivity was abolished. Treatment of ToBRFV-contaminated soil with an alkaline chlorinated-trisodium phosphate solution profoundly reduced soil-mediated virus infection of root-truncated tomato seedlings. Conclusions pH values above 10 compromised ToBRFV particle morphology, genome integrity, and virus infectivity. An alkaline disinfectant enhanced soil remediation following natural ToBRFV contamination.

During our search for aphid-pathogenic viruses, a comovirus was isolated from wild asymptomatic Brassica hirta (white mustard) plants harboring a dense population of Brevicoryne brassicae aphids. The transmission-electron-microscopy visualization of purified virions revealed icosahedral particles. The virus was mechanically transmitted to plants belonging to Brassicaceae, Solanaceae, Amaranthaceae, and Fabaceae families, showing unique ringspot symptoms only on B. rapa var. perviridis plants. The complete viral genome, comprised of two RNA segments, was sequenced. RNA1 and RNA2 contained 5921 and 3457 nucleotides, respectively, excluding the 3′ terminal poly-adenylated tails. RNA1 and RNA2 each had one open-reading frame encoding a polyprotein of 1850 and 1050 amino acids, respectively. The deduced amino acids at the Pro-Pol region, delineated between a conserved CG motif of 3C-like proteinase and a GDD motif of RNA-dependent RNA polymerase, shared a 96.5% and 90% identity with the newly identified Apis mellifera-associated comovirus and Arabidopsis latent virus 1 (ArLV1), respectively. Because ArLV1 was identified early in 2018, the B. hirta comovirus was designated as ArLV1-IL-Bh. A high-throughput-sequencing-analyses of the extracted RNA from managed honeybees and three abundant wild bee genera, mining bees, long-horned bees, and masked bees, sampled while co-foraging in a Mediterranean ecosystem, allowed the assembly of ArLV1-IL-Bh, suggesting pollinators’ involvement in comovirus spread in weeds.

Invasive weeds cause significant crop yield and economic losses in agriculture. The highest indirect impact may be attributed to the role of invasive weeds as virus reservoirs within commercial growing areas. The new tobamovirus tomato brown rugose fruit virus (ToBRFV), first identified in the Middle East, overcame the Tm-2 2 resistance allele of cultivated tomato varieties and caused severe damage to crops. In this study, we determined the role of invasive weed species as potential hosts of ToBRFV and a mild strain of pepino mosaic virus (PepMV-IL). Of newly tested weed species, only the invasive species Solanum elaeagnifolium and S . rostratum , sap inoculated with ToBRFV, were susceptible to ToBRFV infection. S . rostratum was also susceptible to PepMV-IL infection. No phenotype was observed on ToBRFV-infected S . elaeagnifolium grown in the wild or following ToBRFV sap inoculation. S . rostratum plants inoculated with ToBRFV contained a high ToBRFV titer compared to ToBRFV-infected S . elaeagnifolium plants. Mixed infection with ToBRFV and PepMV-IL of S . rostratum plants, as well as S . nigrum plants (a known host of ToBRFV and PepMV), displayed synergism between the two viruses, manifested by increasing PepMV-IL levels. Additionally, when inoculated with either ToBRFV or PepMV-IL, disease symptoms were apparent in S . rostratum plants and the symptoms were exacerbated upon mixed infections with both viruses. In a bioassay, ToBRFV-inoculated S . elaeagnifolium , S . rostratum and S . nigrum plants infected tomato plants harboring the Tm-2 2 resistant allele with ToBRFV. The distribution and abundance of these Solanaceae species increase the risks of virus transmission between species.

Carrots collected from the Western Negev region in Israel during the winter of 2019 showed disease symptoms of chlorosis, leaf curling, a loss of apical dominance, and multiple lateral roots that were not associated with known pathogens of the carrot yellows disease. Symptomatic carrots were studied for a possible involvement of plant viruses in disease manifestations using high throughput sequencing analyses. The results revealed the presence of a waikavirus, sharing a -70% nucleotide sequence identity with Waikavirus genus members. Virions purified from waikavirus-positive carrots were visualized by transmission electron microscopy, showing icosahedral particle diameter of -28 nm. The genome sequence was validated by overlapping amplicons by designed 12 primer sets. A complete genome sequence was achieved by rapid amplification of cDNA ends (RACE) for sequencing the 5 & PRIME; end, and RT-PCR with oligo dT for sequencing the 3 & PRIME; end. The genome encodes a single large ORF, characteristic of waikaviruses. Aligning the waikavirus-deduced amino-acid sequence with other waikavirus species at the Pro-Pol region, a conserved sequence between the putative proteinase and the RNAdependent RNA polymerase, showed a -40% identity, indicating the identification of a new waikavirus species. The amino-acid sequence of the three coat proteins and cleavage sites were experimentally determined by liquid chromatography-mass spectrometry. A phylogenetic analysis based on the Pro-Pol region revealed that the new waikavirus clusters with persimmon waikavirus and actinidia yellowing virus 1. The new waikavirus genome was localized in the phloem of waikavirus-infected carrots. The virus was transmitted to carrot and coriander plants by the psyllid Bactericera trigonica Hodkinson (Hemiptera: Triozidae).

Tomato brown rugose fruit virus (ToBRFV) is a soil-borne virus showing a low percentage of ca. 3% soil-mediated infection when the soil contains root debris from a previous 30–50 day growth cycle of ToBRFV-infected tomato plants. We designed stringent conditions of soil-mediated ToBRFV infection by increasing the length of the pre-growth cycle to 90–120 days, adding a ToBRFV inoculum as well as truncating seedling roots, which increased seedling susceptibility to ToBRFV infection. These rigorous conditions were employed to challenge the efficiency of four innovative root-coating technologies in mitigating soil-mediated ToBRFV infection while avoiding any phytotoxic effect. We tested four different formulations, which were prepared with or without the addition of various virus disinfectants. We found that under conditions of 100% soil-mediated ToBRFV infection of uncoated positive control plants, root-coating with formulations based on methylcellulose (MC), polyvinyl alcohol (PVA), silica Pickering emulsion and super-absorbent polymer (SAP) that were prepared with the disinfectant chlorinated-trisodium phosphate (Cl-TSP) showed low percentages of soil-mediated ToBRFV infection of 0%, 4.3%, 5.5% and 0%, respectively. These formulations had no adverse effect on plant growth parameters when compared to negative control plants grown under non ToBRFV inoculation conditions.

The tobamovirus tomato brown rugose fruit virus (ToBRFV) infects tomato plants harboring the Tm-22 resistance allele, which corresponds with tobamoviruses’ avirulence (Avr) gene encoding the movement protein to activate a resistance-associated hypersensitive response (HR). ToBRFV has caused severe damage to tomato crops worldwide. Unlike tomato plants, pepper plants harboring the L resistance alleles, which correspond with the tobamovirus Avr gene encoding the coat protein, have shown HR manifestations upon ToBRFV infection. We have found that ToBRFV inoculation of a wide range of undefined pepper plant varieties could cause a “hypersensitive-like cell death” response, which was associated with ToBRFV transient systemic infection dissociated from disease symptom manifestations on fruits. Susceptibility of pepper plants harboring L1, L3, or L4 resistance alleles to ToBRFV infection following HRs was similarly transient and dissociated from disease symptom manifestations on fruits. Interestingly, ToBRFV stable infection of a pepper cultivar not harboring the L gene was also not associated with disease symptoms on fruits, although ToBRFV was localized in the seed epidermis, parenchyma, and endothelium, which borders the endosperm, indicating that a stable infection of maternal origin of these tissues occurred. Pepper plants with systemic ToBRFV infection could constitute an inoculum source for adjacently grown tomato plants.

The tobamoviruses tomato brown rugose fruit virus (ToBRFV) and cucumber green mottle mosaic virus (CGMMV) have caused severe crop damages worldwide. Soil-mediated dispersion of the mechanically transmitted tobamoviruses constitute a major hindrance toward mitigating disease spread in crops carefully planted under sanitized conditions. Tobamoviruses are viable for months in soil and plant debris and for more than a year adhere to clay. However, a low percentage of infectious foci occur in soil following a tobamovirus-infected growing cycle, rendering disinfection studies of several contaminated plots inconclusive for large-scale crop productions. We have therefore formulated a rigorous platform for studying disinfectant efficacy in greenhouses by pouring a virus inoculum to planting pits prior to disinfectant treatment and by truncating seedling roots before planting, which was otherwise conducted under sanitized conditions. We have found that chlorine-based Taharan was significantly efficient in preventing disease spread of ToBRFV and CGMMV in tomato and cucumber plants, respectively. KlorBack was often as good as Taharan. In addition, a formulation of chlorinated tri-sodium phosphate used at a nonphytotoxic 3% concentration showed disinfection efficiency similar to Taharan effect on ToBRFV infection only. Our study provided a small-scale platform for disinfectant efficacy evaluation necessary for application in tobamovirus-contaminated soil, which commonly occurs in commercial tomato and cucumber greenhouses.

The efficiency of epitope-based vaccination (subunit vaccines) is tightly correlated with heterogeneity and the high density of epitope presentation, which maximizes the potential antigenic determinants. Here, we developed a two-mode platform for intensifying the epitope presentation of subunit vaccines. The two-mode epitope presentation enhancement includes a covalent attachment of high concentrations of SARS-CoV-2-S1 peptide epitope to the surface of virus-like-particles (VLPs) and the subsequent assembly of VLP/epitope conjugates on the oil droplet surface at an oil/water interface of an emulsion as Pickering stabilizers. The resultant emulsions were stable for weeks in ambient conditions, and our platform was challenged using the epitope of the SARS-CoV-2-S1 peptide that served as a model epitope in this study. In vivo assays showed that the αSARS-CoV-2-S1 immunoglobulin G (IgG) titers of the studied mouse antisera, developed against the SARS-CoV-2-S1 peptide under different epitope preparation conditions, showed an order of magnitude higher IgG titers in the studied VLP-based emulsions than epitopes dissolved in water and epitopes administered with an adjuvant, thereby confirming the efficacy of the formulation. This VLP-based Pickering emulsion platform is a fully synthetic approach that can be readily applied for vaccine development to a wide range of pathogens.

Greenhouse-grown cucumber plants inspected during and following extreme variations in environmental temperatures showed new characteristics of cucumber green mottle mosaic virus (CGMMV) disease manifestations. An increasing occurrence of CGMMV disease recovery has been associated with a new phenotype, identified at early stages of a reemerging disease. Symptoms of bright yellow islands (BYIs), conspicuous amid a dark green surrounding tissue (DGS), were detected in up to 10% of symptomatic plants in net-houses showing 50–60% recovery following an extreme temperature wave. Importantly, similar CGMMV disease initiation stages were observed in infected cucumber plants exposed to low temperatures of ~16 °C, under conditions of both controlled growth chambers and a net-house exposed to environmental temperature fluctuations. Apparently, a wide range of fluctuating temperatures evoked gradual manifestations of a reemerging disease.

Studies of early stages of cucumber green mottle mosaic virus (CGMMV) disease have been recently focused on plant molecular responses. However, extreme diurnal environmental temperatures, characteristic of global climate changes, could affect plant susceptibility and disease phenotype progression. Our studies of CGMMV disease progression, under simulated extreme temperature waves, have revealed two new disease initiation phenotypes that developed gradually, preceding severe symptom manifestations of post-recovery CGMMV systemic infections. 'Early post-recovery stage' bright yellow islands (BYIs) with defined boundaries amid asymptomatic leaf blades were first emerging followed by 'late post-recovery stage' BYIs with diffused boundaries. A deduced CGMMV disease progression scheme, postulating BYI symptom occurrence time-windows, revealed BYIs in field grown cucumber plants exposed to extreme diurnal temperatures. Profiling ontology of cucumber differentially expressed genes in BYIs vs the associated dark-green surrounding tissues disclosed activation of jasmonic acid (JA) pathway in 'early post-recovery stage' BYIs. JA signaling was inactivated in 'late post-recovery stage' BYIs concomitant with increasing expressions of JA signaling inhibitors and downregulation of JA responsive phenylpropanoid pathway. Our results disclosed a new phenotypic description of CGMMV disease initiation, characteristic of cucumbers grown under extreme environmental temperature fluctuations. The BYI phenotypes could define a time-window for CGMMV disease management applications.

The tobamovirus tomato brown rugose fruit virus (ToBRFV), a major threat to tomato production worldwide, has recently been documented in mixed infections with the potexvirus pepino mosaic virus (PepMV) CH2 strain in traded tomatoes in Israel. A study of greenhouse tomato plants in Israel revealed severe new viral disease symptoms including open unripe fruits and yellow patched leaves. PepMV was only detected in mixed infections with ToBRFV in all 104 tested sites, using serological and molecular analyses. Six PepMV isolates were identified, all had predicted amino acids characteristic of CH2 mild strains excluding an isoleucine at amino acid position 995 of the replicase. High-throughput sequencing of viral RNA extracted from four selected symptomatic plants showed solely the ToBRFV and PepMV, with total aligned read ratios of 40.61% and 11.73%, respectively, indicating prevalence of the viruses. Analyses of interactions between the co-infecting viruses by sequential and mixed viral inoculations of tomato plants, at various temperatures, showed a prominent increase in PepMV titers in ToBRFV pre-inoculated plants and in mixed-infected plants at 18–25 °C, compared to PepMV-single inoculations, as analyzed by Western blot and quantitative RT-PCR tests. These results suggest that Israeli mild PepMV isolate infections, preceded by ToBRFV, could induce symptoms characteristic of PepMV aggressive strains.

A new virus belonging to the family Dicistroviridae was identified in the hibiscus-infesting cotton mealybug Phenacoccus solenopsis. Using high-throughput sequencing (HTS) on an Illumina HiSeq platform, a single contig of the complete genome sequence was assembled. The authenticity of the sequence obtained by HTS was validated by RT-PCR and Sanger sequencing of the amplicons, which was also employed for the 3’ untranslated region (UTR). The 5’ UTR was sequenced using a rapid amplification of cDNA ends kit. A large segment encompassing the whole genome was amplified by RT-PCR using viral RNA extracted from mealybugs. A whole-genome nucleotide sequence comparison showed 89% sequence identity to aphid lethal paralysis virus (ALPV), covering a short segment of 44 bp. Pairwise amino acid sequence comparisons of the protein encoded by open reading frame (ORF) 2 with its counterparts in the GenBank database, showed less than 40% identity to several members of the genus Cripavirus, including ALPV. Phylogenetic analysis based on the deduced amino acid sequence of the ORF 2 protein showed that the new virus grouped with members of the genus Cripavirus. The intergenic region (IGR) internal ribosome entry site (IRES) showed the conserved nucleotides of a type I IGR IRES and had two bulge sites, three pseudoknots, and two stem-loops. Virus morphology visualized by transmission electron microscopy demonstrated spherical particles with a diameter of ~30 nm. This virus was the only arthropod virus identified in the sampled mealybugs, and the purified virus was able to infect cotton mealybugs. To the best of our knowledge, this is the first report of a Dicistroviridae family member infecting P. solenopsis, and we have tentatively named this virus Phenacoccus solenopsis virus (PhSoV).

Cucumber green mottle mosaic virus (CGMMV) assigned to the genus Tobamovirus is considered a major disease cause of cucurbits worldwide. A primary route for CGMMV disease spread is via mechanical contact. The virus is highly stable and adheres to various agricultural equipment. In the current study, we examined means to inactivate the virus and reduce disease spread via planting equipment and supplies using various chemicals. We have found that incubations of CGMMV-infected cucumber plant extracts with MENNO-Florades 2%, Virocid 3% or Green Up D 20% inactivated the virus and prevented disease spread in a biological assay. Stabilised chlorine formulation (KlorBac), which has the active ingredient troclosene-sodium (sodium dichloroisocyanurate, SDIC) at 2,000 ppm, was efficient in disinfecting CGMMV-contaminated grafting knives in 2 s. Similarly, immersing virus contaminated grafting knives for 2 s in 20% (wt/vol) non-fat milk powder reduced infectivity of the contaminated knives. CGMMV-contaminated nursery sowing trays could constitute a primary infectious viral source transmitted via irrigation water. CGMMV-contaminated sowing trays immersed in KlorBac 2,000 ppm or active oxygen (Huwa-San TR-50) 1%, were efficiently disinfected. Interestingly, hydrophobic insulation of the CGMMV-contaminated trays using dry silicone layers reduced initiation of the viral primary infection in CGMMV-contaminated new sowing trays but was less efficient in CGMMV-contaminated re-used trays. Importantly, Septadine (0.5% chlorhexidine gluconate) was not effective in disinfection of grafting knives. Notably, CGMMV-infected cucumber plant extract incubated with 20% (wt/vol) non-fat milk powder was refractory to the milk suggesting that virus release from surfaces did not necessarily involve virus inactivation.

During 2019, tomato fruits showing viral-like symptoms of marbled yellow spots were abundant in Israel. The new symptoms were distinctive from those typical of tomato brown rugose fruit virus (ToBRFV) infection but resembled symptoms of pepino mosaic virus (PepMV) infection. RT-PCR analysis and the serological tests (enzyme linked immunosorbent assay, western blot and in situ immunofluorescence) revealed and confirmed the presence of both the tobamovirus ToBRFV and the potexvirus PepMV in the symptomatic fruits. A mixture of rod-like and filamentous particles, characteristic of viruses belonging to tobamovirus and potexvirus genera, was visualized by transmission electron microscopy of the tomato fruit viral extract. Sanger sequencing of amplified PepMV-coat protein gene segments showed ~98% sequence identity to the Chilean (CH2)-strain. In a biological assay testing the contribution of traded infected tomatoes to the establishment of tomato plant disease, we applied direct and indirect inoculation modes using Tm-22-resistant tomato plants. The results, assessed by disease symptom development along with serological and molecular analyses, showed that the ToBRFV and PepMV co-infected fruits were an effective inoculum source for disease spread only when fruits were damaged. Importantly, intact fruits did not spread the viral disease. These results added a new factor to disease epidemiology of these viruses.

In a survey conducted in Cannabis sativa L. (cannabis) authorized farms in Israel, plants showed disease symptoms characteristic of nutrition deprivation. Interveinal chlorosis, brittleness, and occasional necrosis were observed in older leaves. Next generation sequencing analysis of RNA extracted from symptomatic leaves revealed the presence of lettuce chlorosis virus (LCV), a crinivirus that belongs to the Closteroviridae family. The complete viral genome sequence was obtained using RT-PCR and Rapid Amplification of cDNA Ends (RACE) PCR followed by Sanger sequencing. The two LCV RNA genome segments shared 85–99% nucleotide sequence identity with LCV isolates from GenBank database. The whitefly Bemisia tabaci Middle Eastern Asia Minor1 (MEAM1) biotype transmitted the disease from symptomatic cannabis plants to un-infected ‘healthy’ cannabis, Lactuca sativa, and Catharanthus roseus plants. Shoots from symptomatic cannabis plants, used for plant propagation, constituted a primary inoculum of the disease. To the best of our knowledge, this is the first report of cannabis plant disease caused by LCV.