Tomato Mosaic Virus Research Articles

Detection, Identification and Molecular Characterization of Tomato Mosaic Virus (ToMV) Isolates from Pakistan.

Tomato mosaic virus (ToMV) is one of the lethal tomato pathogens. In this study, we collected tomato leaves exhibiting interveinal chlorosis from farmer’s fields in district Lahore, Pakistan. The presence of tobamoviruses was confirmed through extracting RNA, cDNA synthesis, PCR amplification and subsequent sequencing of capsid protein (CP) gene of ToMV that contained 480 nucleotides (encoded for 160 amino acids making ~17 kDa protein) located at 5703rd to 6182nd nucleotide position in ToMV genome. In sequence analysis, Pakistani isolates shared 98.9-99.5% and 97.3-99.3% nucleotide and amino acid homologies with each other and 96-99% and 90-98.6% with other isolates respectively. In phylogenetic analysis the Pakistani isolates grouped with Iranian and Chines isolates, exhibiting higher nucleotides and amino acids identities as well. This research reveals a geographical association among Pakistani, Chines and Iranian ToMV isolates. The study suggests extensive surveys of tobamoviruses infecting field crops for their detailed genetic information.

Konya İli Ereğli İlçesi Domates Ekim Alanlarında Domateste Yaygın Olarak Bulunan Üç Virüsün Serolojik Tespiti

In this study, it was aimed to reveal some viruses that are a problem in tomato production areas in the Ereğli district of Konya, where tomato production is common. For this reason, in the 2019 production season, leaf samples were taken from 160 tomato plants showing symptoms similar to virus disease symptoms such as mosaic, deformations, yellowing, blight on the leaves and stunted plants. Possible infections of Cucumber mosaic virus (CMV), Tomato spotted-wilt virus (TSWV) and Tomato mosaic virus (ToMV) on these leaves were tested by serological-based DAS-ELISA (Double Antibody Sandwich- Enzyme Linked Immuno Sorbent Assay) method. According to DAS-ELISA results, it was determined that 66.25% of the samples were infected with at least one of these three viruses. In addition, TSWV was detected as the most common virus with a 48.75% relative infection rate in the samples, followed by ToMV (28.75%) and CMV (26.25%). Mixed infections of the viruses were also detected in the leaf samples tested. CMV + TSWV double infection was detected in 22 samples, ToMV + TSWV double infection was detected in 14 samples, and CMV + ToMV + TSWV triple infection was detected in 12 plant samples.

Controlling Pepper Mild Mottle Virus (PMMoV) Infection in Pepper Seedlings by Use of Chemically Synthetic Silver Nanoparticles

We investigated the roles of different concentrations of chemical synthetic spherical silver nanoparticles (AgNPs) in protecting pepper seedlings of the Mecca region, which were naturally and artificially infected by the pepper mild mottle virus (PMMoV). The virus shows many infection symptoms, including pepper leaf deformation with filiform leaves and severe mosaic symptoms. Our study focused on the antiviral activity of different concentrations of spherical nanoparticles in controlling PMMoV infecting pepper seedlings. PMMoV identification was confirmed via DAS-ELISA using the following antiserum: PMMoV, cucumber mosaic virus (CMV), tobacco mosaic virus (TMV), tomato mosaic virus (ToMV), potato virus Y (PVY), and tomato spotted wilt virus (TSWV). The presence of PMMoV was confirmed using electron microscopy and reverse transcription polymerase chain reaction (RT-PCR). We evaluated the effects of exogenously applied different concentrations of AgNPs on CMV infection rate, infection severity, virus concentration, and the concentrations of photosynthetic pigments chlorophyll a, chlorophyll b, carotenoid content, phenolic compounds, and protein components in virus-infected plant cells that were treated with three different concentration of nanoparticles (200, 300, and 400 µg/L) compared to the positive and negative control.

Molecular characterization of wild tomato mosaic virus and chilli veinal mottle virus mix‐infecting chilli pepper in China

AbstractThe present study described molecular characterization of two potyviruses: wild tomato mosaic virus Dehong isolate (WTMV‐Dh) and chilli veinal mottle virus Dehong isolate (ChiVMV‐Dh) mix‐infection chilli pepper and assessed their mix‐infection on chilli pepper. Transcriptome next‐generation sequencing technology (NGS) and RT‐PCR were used to obtain the complete genome sequences of the abovementioned two viruses. The results showed that the complete sequence of WTMV‐Dh is 9675 nucleotides (nt) in length and encodes a complete polyprotein of 3075 amino acids (aa). The WTMV‐Dh polyprotein shares 76.1%–82.6% nt and 85.3%–89.5% aa identities with three previously reported WTMV isolates. The complete sequence of ChiVMV‐Dh is 9736 nt in length and encodes a complete polyprotein with 3, 089 aa. ChiVMV‐Dh polyprotein shares 80.8%–92.2% nt and 85.3%–95.6% aa identities with previously reported ChiVMV isolates. Following phylogenetic analysis based on the polyprotein sequences of potyviruses revealed that WTMV‐Dh clustered with the Vietnam strain WTMV‐Laichau, while ChiVMV‐Dh clustered with several ChiVMV Sichuan isolates. The mix‐inoculation experiment showed that the mix‐infection of these two viruses has more severe symptoms than single‐infection.

Calcium nutrition nanoagent rescues tomatoes from mosaic virus disease by accelerating calcium transport and activating antiviral immunity.

As an essential structural, metabolic and signaling element, calcium shows low remobilization from old to young tissues in plants, restricting the nutrient-use efficiency and control efficacy against mosaic virus disease. Nanotechnology has been applied to prevent/minimize nutrient losses and improve the accessibility of poorly-available nutrients. Herein, the current study applied a star polycation (SPc) to prepare a calcium nutrition nanoagent. The SPc could assemble with calcium glycinate through hydrogen bond and Van der Waals force, forming stable spherical particles with nanoscale size (17.72 nm). Transcriptomic results revealed that the calcium glycinate/SPc complex could activate the expression of many transport-related genes and disease resistance genes in tomatoes, suggesting the enhanced transport and antiviral immunity of SPc-loaded calcium glycinate. Reasonably, the calcium transport was accelerated by 3.17 times into tomato leaves with the help of SPc, and the protective effect of calcium glycinate was remarkably improved to 77.40% and 67.31% toward tomato mosaic virus with the help of SPc after the third and fifth applications. Furthermore, SPc-loaded calcium glycinate could be applied to increase the leaf photosynthetic rate and control the unusual fast growth of tomatoes. The current study is the first success to apply nano-delivery system for enhanced calcium transport and antiviral immunity, which is beneficial for increasing nutrient-use efficiency and shows good prospects for field application.

Elicitation of Hyoscyamine Production in Datura stramonium L. Plants Using Tobamoviruses

Datura stramonium L. produces tropane alkaloids, and the hyoscyamine is dominant among them. Hyoscyamine is produced by hairy root cultures in vitro derived from native plants or plants with the genetically modified biosynthetic pathway for hyoscyamine. A common procedure is extraction from cultivated plants. Elicitors for increased production can be used in both cases. Live viruses are not well known for use as elicitors, therefore, D. stramonium plants grown in soil were artificially infected with the tobamoviruses Pepper mild mottle virus (PMMoV), Tomato mosaic virus (ToMV), and Tobacco mosaic virus (TMV). Differences in the content of hyoscyamine were between capsules and roots of infected and non-infected plants. Elicitation increased content of hyoscyamine in capsules 1.23-2.34 times, compared to the control. The most effective viruses were PMMoV and ToMV (isolate PV143), which increased content to above 19 mg/g of fresh weight of a capsule. The effect of each virus elicitor was expressed also in hyoscyamine content in roots. Elicited plants contained 5.41-16.54 times more hyoscyamine in roots compared to non-elicited plants. The most effective elicitor was ToMV SL-1, which raised production above 20 mg/g fresh weight of roots. It has been shown that tobamoviruses can be used as biotic elicitors.

Sequencing and Variant Detection of Eight Abundant Plant-Infecting Tobamoviruses across Southern California Wastewater.

Tobamoviruses are agriculturally relevant viruses that cause crop losses and have infected plants in many regions of the world. These viruses are frequently found in municipal wastewater, likely coming from human diet and industrial waste across wastewater catchment areas. As part of a large wastewater-based epidemiology study across Southern California, we analyzed RNA sequence data from 275 influent wastewater samples obtained from eight wastewater treatment plants with a catchment area of approximately 16 million people from July 2020 to August 2021. We assembled 1,083 high-quality genomes, enumerated viral sequencing reads, and detected thousands of single nucleotide variants from eight common tobamoviruses: bell pepper mottle virus, cucumber green mottle mosaic virus, pepper mild mottle virus, tobacco mild green mosaic virus, tomato brown rugose fruit virus, tomato mosaic virus, tomato mottle mosaic virus, and tropical soda apple mosaic virus. We show that single nucleotide variants had amino acid-altering consequences along with synonymous mutations, which represents potential evolution with functional consequences in genomes of these viruses. Our study shows the importance of wastewater sequencing to monitor the genomic diversity of these plant-infecting viruses, and we suggest that our data could be used to continue tracking the genomic variability of such pathogens. IMPORTANCE Diseases caused by viruses in the genus Tobamovirus cause crop losses around the world. As with other viruses, mutation occurring in the virus's genomes can have functional consequences and may alter viral infectivity. Many of these plant-infecting viruses have been found in wastewater, likely coming from human consumption of infected plants and produce. By sequencing RNA extracted from influent wastewater obtained from eight wastewater treatment plants in Southern California, we assembled high-quality viral genomes and detected thousands of single nucleotide variants from eight tobamoviruses. Our study shows that Tobamovirus genomes vary at many positions, which may have important consequences when designing assays for the detection of these viruses by agricultural or environmental scientists.

The Characterization of the Tobacco-Derived Wild Tomato Mosaic Virus by Employing Its Infectious DNA Clone.

Simple SummaryWild tomato mosaic virus (WTMV, genus Potyvirus, family Potyviridae) is an emerging viral pathogen that endangers Nicotiana tabacum production. The field survey conducted in this study shows that WTMV is becoming an epidemic in China. An infectious DNA clone of the tobacco-derived WTMV is constructed. It can infect wild eggplant, black nightshade, and tobacco plants but can not infect various local pepper varieties. WTMV evolves into three groups that coincide with their original hosts, tobacco, pepper, or wild eggplant. Thus, the tobacco-derived WTMV might divergently evolves to adapt to tobacco other than peppers. We show that WTMV is compatible with the coinfection of cucumber mosaic virus (CMV) or tobacco mosaic virus (TMV) in tobacco but not other potyviruses. Specifically, WTMV can interfere with the infection of other potyvirus species in tobacco, a phenomenon known as superinfection exclusion previously observed within the same potyviral species. This study contributes essential knowledge on the evolution, infectivity, and recent epidemics of WTMV, and provides the key tool for further disease-resistance and field management studies.Viral diseases of cultivated crops are often caused by virus spillover from wild plants. Tobacco (N. tabacum) is an important economic crop grown globally. The viral pathogens of tobacco are traditional major subjects in virology studies and key considerations in tobacco breeding practices. A positive-strand RNA virus, wild tomato mosaic virus (WTMV), belonging to the genus potyvirus in the family potyviridae was recently found to infect tobacco in China. In this study, diseased tobacco leaf samples were collected in the Henan Province of China during 2020–2021. Several samples from different locations were identified as WTMV positive. An infectious DNA clone was constructed based on one of the WTMV isolates. By using this clone, we found that WTMV from tobacco could establish infections on natural reservoir hosts, demonstrating a possible route of WTMV spillover and overwintering in the tobacco field. Furthermore, the WTMV infection was found to be accompanied by other tobacco viruses in the field. The co-inoculation experiments indicate the superinfection exclusion (SIE) between WTMV and other potyvirus species that infect tobacco. Overall, our work reveals novel aspects of WTMV evolution and infection in tobacco and provides an important tool for further studies of WTMV.

Bioinformatic-based approach for mutagenesis of plant immune Tm-22 receptor to confer resistance against tomato brown rugose fruit virus (ToBRFV).

Nucleotide-binding leucine-rich repeat (NLR) plant immune receptors mediate the recognition and activation of defense signaling pathways in response to intra- and extracellular pathogens. Several NLR such as Tm-2 and Tm-22 have been introgressed into commercial solanaceous varieties to confer protection against different tobamoviruses. Particularly, Tm-22 was used during recent decades to confer resistance against tobacco mosaic virus, tomato mottle mosaic virus and tomato mosaic virus, which recognizes the viral movement protein (MP). However, tomato brown rugose fruit virus(ToBRFV), a novel tobamovirus, can avoid the protection conferred by Tm-22 due to the presence of key substitutions in the MP. The aim of this work was to identify the key amino acid residues involved in the interaction between Tm-22 and ToBRFV MP through bioinformatic analyses, and to identify potential Tm-22 mutations that could generate greater binding affinity. In silico 3D structure prediction, molecular docking, and computational affinity methods were performed. We predicted that R350, H384 and K385 Tm-22 residues are relevant for the interaction with MP, and two mutations (H384W and K385L) were identified as putative sites to increase the affinity of Tm-22 to the MP with the potential elicitation of resistance against ToBRFV.

A Machine Intelligent Based Approach for the Classification and Analysis of Tomato Leaf Disease Images

Purpose: Vegetable production plays a vital role for the existence of human society. It is very much essential for the proper care of vegetable plants for better production of vegetables. However, vegetable plant leaf disease is a major concern in the current scenario. Tomato leaf disease is one of them. So, preventive measures should be taken to avoid the rise of tomatoes and other leaf diseases at the earliest for better production of vegetables. Approach: In this work, a machine intelligent (MI) based approach is proposed for the classification of tomato leaf disease images (TLDIs) into the bacterial spot (BS), early blight (EB), late blight (LB), leaf mold (LM), septoria leaf spot (SLS), tomato mosaic virus (TMV), tomato yellow leaf curl virus (TYLCV) and healthy (HL) types. The proposed approach is focused on the stacking (hybridization) of Logistic Regression (LRG), Support Vector Machine (SVMN), Random Forest (RFS) and Neural Network (NNT) methods to carry out such classification. The proposed method is compared with other machine learning (ML) based methods such as LRG, SVMN, RFS, NNT, Decision Tree (DTR), AdaBoost (ADB), Naïve Bayes (NBY), K-Nearest Neighbor (KNNH) and Stochastic Gradient Descent (SGDC) for performance analysis. Result: The proposed method and other ML based methods have been implemented using Python based Orange 3.26.0. In this work, 1600 TLDIs having 200 numbers of each type such as BS, EB, LB, LM, SLS, TMV, TYLCV and HL are taken from the Kaggle source. The performance of all the methods is assessed using the performance parameters such as classification accuracy (CA), F1, Precision (PR) and Recall (RC). From the results, it is found that the proposed method is capable of providing better classification results in terms of CA, F1, PR and RC as compared to other ML based methods such as LRG, SVMN, RFS, NNT, DTR, ADB, NBY, KNNH and SGD. Originality: In this work, a MI based approach is proposed by focusing on the stacking of LRG, SVMN, RFS and NNT methods to carry out the classification of TLDIs into several types such as BS, EB, LB, LM, SLS, TMV, TYLCV and HL. The proposed approach performs better in terms of CA, F1, PR and RC as compared to LRG, SVMN, RFS, NNT, DTR, ADB, NBY, KNNH and SGDC methods. Paper Type: Conceptual Research.

Induction of Systemic Resistance to Tobacco mosaic virus in Tomato through Foliar Application of Bacillus amyloliquefaciens Strain TBorg1 Culture Filtrate.

The application of microbe-derived products as natural biocontrol agents to boost systemic disease resistance to virus infections in plants is a prospective strategy to make agriculture more sustainable and environmentally friendly. In the current study, the rhizobacterium Bacillus amyloliquefaciens strain TBorg1 was identified based on 16S rRNA, rpoB, and gyrA gene sequences, and evaluated for its efficiency in conferring protection of tomato from infection by Tobacco mosaic virus (TMV). Under greenhouse circumstances, foliar sprays of TBorg1 culture filtrate (TBorg1-CF) promoted tomato growth, lowered disease severity, and significantly decreased TMV accumulation in systemically infected leaves of treated plants relative to untreated controls. TMV accumulation was reduced by 90% following the dual treatment, applied 24 h before and after TMV infection. Significant increases in levels of total soluble carbohydrates, proteins, and ascorbic acid were also found. In addition, a significant rise in activities of enzymes capable of scavenging reactive oxygen species (PPO and POX), as well as decreased levels of non-enzymatic oxidative stress markers (H2O2 and MDA) were observed, compared to untreated plants. Enhanced systemic resistance to TMV was indicated by significantly increased transcript accumulation of polyphenolic pathway (C4H, HCT, and CHI) and pathogenesis-related (PR-1 and PR-5) genes. Out of the 15 compounds identified in the GC-MS analysis, 1,2-benzenedicarboxylic acid mono(2-ethylhexyl) ester and phenol, 2,4-bis(1,1-dimethylethyl), as well as L-proline, N-valeryl-, and heptadecyl ester were present in the highest concentrations in the ethyl acetate extract of TBorg1-CF. In addition, significant amounts of n-hexadecanoic acid, pyrrolo [1,2-a] pyrazine-1,4-dione hexahydro-3-(2-methylpropyl)-, nonane, 5-butyl-, and eicosane were also detected. These compounds may act as inducers of systemic resistance to viral infection. Our findings indicate that the newly isolated B. amyloliquefaciens strain TBorg1 could be a potentially useful rhizobacterium for promoting plant growth and a possible source of biocontrol agents for combating plant virus infections.

Screening a collection of local and foreign varieties of Solanum lycopersicum L. in Kazakhstan for genetic markers of resistance against three tomato viruses

The tomato is one of the most important vegetable crops. The successful development of tomato cultures in Kazakhstan depends on the implementation of intensive agricultural methods, including breeding and selecting for new tomato varieties resistant to plant pathogens. Common tomato viruses, although not detected in our country to date, may potentially have a deleterious impact on agriculture if allowed to spread. The implementation of tomato breeding programs based on molecular markers of resistance is therefore an important preventive measure for protecting the agriculture and food safety of Kazakhstan. In the present work, we used nine molecular markers associated with resistance to three tomato viruses, i.e., tomato mosaic virus (ToMV), tomato spot wilt virus (TSWV), and tomato yellow leaf curl virus (TYLCV), to test the local breeding collection for the presence of genetic resistance factors. Two tomato varieties, ‘Zhiraf’ (Russia) and ‘Sunnik’ (Armenia), were revealed to possess the resistant allele marker PrRuG86-151 against ToMV; three hybrid forms had the same allele in the heterozygous state. One hybrid, based on the ‘Mirsini’ F1 variety from the Netherlands, had resistance to TSWV, which was confirmed by four markers: NCSw003, NCSw007, NCSw011, and NCSw012. Two cultivars, ‘Nicola’ and ‘Malinovyi Slon’ (Russia), and the local hybrid based on ‘Yarkiy Rumyanets’ had two to three resistant alleles of markers based on locus Tm-3 of resistance to TYLCV. The obtained results have demonstrated that the collection of tomato varieties involved in breeding programs in Kazakhstan lacks well-known genetic resistance factors to the considered tomato viruses. Thus, the prospective breeding programs require introduction of known resistant genetic resources to establish resistance to viruses using marker-assisted selection.

First report of Chili pepper mild mottle virus in calibrachoa in the United States

Beginning in January 2022, plants of the popular solanaceous ornamental calibrachoa (Calibrachoa spp.) from commercial producers in the United States were observed with various viral disease symptoms including chlorosis, purple mottling and tip necrosis of leaves, and colour-break of flowers (Figures 1, 2). Seventy cuttings of the affected plants were submitted to Agdia Testing Services (Agdia Inc., USA) for analysis and produced positive results with Tobacco mosaic virus ImmunoStrip® (lateral flow immunoassay) and ELISA, Pepper mild mottle virus ImmunoStrip® and ELISA, and Tomato mosaic virus ELISA suggesting the presence of a tobamovirus. To confirm and extend these serological results, total RNA was isolated from seven samples using a modified RNeasy protocol (Qiagen, Germany) and tested using a tobamovirus group RT-PCR (Maroon & Zavriev, 2002). The sequence of the RT-PCR amplicons indicated the presence of the recently described tobamovirus, Chili pepper mild mottle virus (CPMMoV; Vélez-Olmedo et al., 2021). For further characterisation, total RNA from four calibrachoa samples (two each from two different greenhouses located in two different states) representing four different calibrachoa varieties were selected for additional RT-PCR testing at USDA-ARS with degenerate tobamovirus primers. Amplicons of c. 200 bp were observed from all samples with the tob4404v and tob4593 primers (Adkins et al., 2018) designed to amplify a conserved portion of the replicase gene. Similarly, amplicons of c. 800 bp were observed from all samples with the SolACPv and SolACPvc primers (Chellemi et al., 2011) designed to amplify the 3′ terminus of the movement protein gene, the entire coat protein (CP) gene, and part of the 3′ UTR. Amplicons were directly sequenced (GenBank Accession Nos. ON381946-ON381953) and those from each primer set shared 99–100% nucleotide identity with each other, and 99–100% nucleotide identity with the corresponding regions of CPMMoV isolate Oxampampa4 (MN164455) confirming the presence of this tobamovirus. CPMMoV-specific CP gene primers (Vélez-Olmedo et al., 2021) also produced amplicons of the expected size, c. 1,100 bp. No other tobamovirus sequences were detected with any of these primer sets. We additionally tested the same four samples with degenerate potyvirus (Gibbs & Mackenzie, 1997) and orthotospovirus (Chu et al., 2001) primers; no amplicons were observed. CPMMoV was first reported in 2021 from field-grown pepper in Peru (Vélez-Olmedo et al., 2021). To the best of our knowledge, this is the first report of CPMMoV in calibrachoa or any other greenhouse-grown ornamental host. Further research is necessary to determine the prevalence of CPMMoV in ornamental and vegetable crop hosts, and the potential impact this tobamovirus may have on these crops. Salvador Lopez and Carrie Vanderspool are acknowledged for their excellent technical assistance.

Occurrence, Genetic Variability of Tomato Yellow Ring Orthotospovirus Population and the Development of Reverse Transcription Loop-Mediated Isothermal Amplification Assay for Its Rapid Detection.

Tomato-infecting viruses have been considered as a serious threat to tomato crops in Poland. Therefore, during 2014–2021, 234 tomato samples delivered directly by greenhouse tomato growers to Plant Disease Clinic of IPP-NRI were tested. Eight virus species: pepino mosaic virus (PepMV), tomato yellow ring orthotospovirus (TYRV), tomato spotted wilt orthotospovirus (TSWV), potato virus Y (PVY), cucumber mosaic virus (CMV), tomato black ring virus (TBRV) and tomato mosaic virus (ToMV) were detected in single or mixed infection in 89 samples. The presence of TYRV was established for the first time in Poland in 2014. Since then, its presence has been observed in single and mixed infection with TSWV and CMV. Here, we analysed the genetic variability of TYRV population based on complete nucleocapsid (N) protein gene sequence of 55 TYRV isolates. Maximum-likelihood reconstruction revealed the presence of three distinct, well-supported phylogroups. Moreover, the effect of host species on virus diversity was confirmed. Therefore, RT-LAMP assay was developed for the rapid and efficient detection of TYRV isolates that can be implemented in field and greenhouse conditions.

Transcriptome Analysis Reveals the Response Mechanism of Frl-Mediated Resistance to Fusarium oxysporum f. sp. radicis-lycopersici (FORL) Infection in Tomato.

Tomato Fusarium crown and root rot (FCRR) is an extremely destructive soil-borne disease. To date, studies have shown that only plants with tomato mosaic virus (TMV) resistance exhibit similar resistance to tomato Fusarium oxysporum f. sp. radicis-lycopersici (FORL) and have identified a single relevant gene, Frl, in Peruvian tomato. Due to the relative lack of research on FCRR disease-resistance genes in China and elsewhere, transcriptome data for FORL-resistant (cv. ‘19912’) and FORL-susceptible (cv. ‘Moneymaker’) tomato cultivars were analysed for the first time in this study. The number of differentially expressed genes (DEGs) was higher in Moneymaker than in 19912, and 189 DEGs in the ‘plant–pathogen interaction’ pathway were subjected to GO and KEGG enrichment analyses. MAPK and WRKY genes were enriched in major metabolic pathways related to plant disease resistance; thus, we focused on these two gene families. In the early stage of tomato infection, the content of JA and SA increased, but the change in JA was more obvious. Fourteen genes were selected for confirmation of their differential expression levels by qRT-PCR. This study provides a series of novel disease resistance resources for tomato breeding and genetic resources for screening and cloning FORL resistance genes.

Characterization of a ToMV isolate overcoming Tm-22 resistance gene in tomato.

Tomato mosaic virus (ToMV) is easily transmitted in soil and by contact. By these reasons, it is relatively difficult to control ToMV disease in tomato. Incorporation of the Tm-22 gene has been widely used as a control method for ToMV, but ToMV isolates that overcome this resistance gene have been reported worldwide in recent years. In this study, we determined the entire nucleotide sequences of ToMV isolate [named ToMV-KMT (LC650928)], which was isolated from tomato plants showing symptoms of systemic necrosis in Kumamoto prefecture, Japan. We also analyzed the viral gene of ToMV-KMT that overcome the Tm-22 gene by constructing its infectious cDNA clone and by generating chimeric viruses with a non-breaking strain. According to previous research, Tm-22 recognizes the viral movement protein (MP) and exerts resistance by inducing hypersensitive reaction or hypersensitive cell death. We discovered that a mutation in the 240th amino acid (aspartic acid to tyrosine) of the MP of ToMV-KMT, which may stabilize the protein's structure, is responsible for the ability of this isolate to overcome the resistance of Tm-22.

Evaluation of New Polyclonal Antibody Developed for Serological Diagnostics of Tomato Mosaic Virus.

Plant viruses threaten agricultural production by reducing the yield, quality, and economical benefits. Tomato mosaic virus (ToMV) from the genus Tobamovirus causes serious losses in the quantity and quality of tomato production. The management of plant protection is very difficult, mainly due to the vector-less transmission of ToMV. Resistant breeding generally has low effectiveness. The most practical approach is the use of a rapid diagnostic assay of the virus’ presence before the symptoms occur in plants, followed by the eradication of virus-infected plants. Such approaches also include serological detection methods (ELISA and Western immunoblotting), where antibodies need to be developed for an immunochemical reaction. The development and characterization of polyclonal antibodies for the detection of ToMV with appropriate parameters (sensitivity, specificity, and cross-reactivity) were the subjects of this study. A new polyclonal antibody, AB-1, was developed in immunized rabbits using the modified oligopeptides with antigenic potential (sequences are revealed) derived from the coat protein of ToMV SL-1. the developed polyclonal antibody. AB-1, showed higher sensitivity when compared with commercially available analogs. It also detected ToMV in infected pepper and eggplant plants, and detected another two tobamoviruses (TMV and PMMoV) and ToMV in soil rhizosphere samples and root residues, even two years after the cultivation of the infected tomato plant.

Knockout of SlTOM1 and SlTOM3 results in differential resistance to tobamovirus in tomato.

During tobamovirus–host coevolution, tobamoviruses developed numerous interactions with host susceptibility factors and exploited these interactions for replication and movement. The plant‐encoded TOBAMOVIRUS MULTIPLICATION (TOM) susceptibility proteins interact with the tobamovirus replicase proteins and allow the formation of the viral replication complex. Here CRISPR/Cas9‐mediated mutagenesis allowed the exploration of the roles of SlTOM1a, SlTOM1b, and SlTOM3 in systemic tobamovirus infection of tomato. Knockouts of both SlTOM1a and SlTOM3 in sltom1a/sltom3 plants resulted in an asymptomatic response to the infection with recently emerged tomato brown rugose fruit virus (ToBRFV). In addition, an accumulation of ToBRFV RNA and coat protein (CP) in sltom1a/sltom3 mutant plants was 516‐ and 25‐fold lower, respectively, than in wild‐type (WT) plants at 12 days postinoculation. In marked contrast, sltom1a/sltom3 plants were susceptible to previously known tomato viruses, tobacco mosaic virus (TMV) and tomato mosaic virus (ToMV), indicating that SlTOM1a and SlTOM3 are not essential for systemic infection of TMV and ToMV in tomato plants. Knockout of SlTOM1b alone did not contribute to ToBRFV and ToMV resistance. However, in triple mutants sltom1a/sltom3/sltom1b, ToMV accumulation was three‐fold lower than in WT plants, with no reduction in symptoms. These results indicate that SlTOM1a and SlTOM3 are essential for the replication of ToBRFV, but not for ToMV and TMV, which are associated with additional susceptibility proteins. Additionally, we showed that SlTOM1a and SlTOM3 positively regulate the tobamovirus susceptibility gene SlARL8a3. Moreover, we found that the SlTOM family is involved in the regulation of plant development.

RELATIVE POTENTIAL OF DIFFERENT PLANT EXTRACTS AND GERMPLASM FOR THE MANAGEMENT OF TOMATO MOSAIC VIRUS DISEASE

Tomato is an important vegetable crop grown on all continents of the world. Tomato mosaic virus disease significantly lowers the yield in the field every year. The present study was conducted to find the resistant germplasm and to evaluate the potential of different plant extracts to manage the Tomato mosaic virus (ToMV) disease in field conditions. Ten tomato genotypes were evaluated against the ToMV disease in field conditions. Out of ten varieties/lines, no one was found highly resistant and two varieties/lines (VRI-575 and Naqeeb) were evaluated as resistant to the disease. Aqueous extracts of three different plants (Azadirachta indica, Calotropis procera and Allium cepa) were potentially evaluated at 1% concentrations by three-times foliar application against the disease. In control, nothing was applied. A significant difference in disease index was observed among plant extracts. The disease significantly decreased with the number of applications. Azadirachta indica was found most effective to manage the disease as compared to the others in field conditions. Allium cepa was found least effective against the ToMV disease. From the present study, it was revealed that Naqeeb and VRI-575 varieties/lines may be used for the future breeding program and extracts of Azadirachta indica may be applied to manage the disease.

Systemic resistance induction of tomato plants against tomato mosaic virus by microalgae

BackgroundTomato mosaic virus (ToMV) is a dangerous disease of tomato (Lycopersicon esculentum) that reduces dramatically the yield. To reduce ToMV infection, microalgal isolates were utilized. Microalgal species (Chlorella vulgaris, Anabaena oryzae, Spirulina platensis, Nostoc linckia and Dunaliella salina) were shown to be responsible for the stimulation of tomato resistance against ToMV.ResultsInitial signs of discoloration and mosaic in ToMV-inoculated plants were detected and identified on inoculated leaves at 6 and 12 dpi in control and treated plants, respectively, suggesting that microalgae may inhibit ToMV growth. Treatment with microalgae resulted in a significant decrease in symptoms (up to 63% reduction in disease severity) and negative ELISA readings, indicating that the microalgae induced resistance in tomato against ToMV infection. The isolates also enhanced the activity of pathogenesis-related enzymes (PPO and POX reaching to 0.033 and 0.054 in D. salina, respectively), as well as tomato growth characters in comparison with the control. Microalgal treatments demonstrated that the salicylic acid (SA) and jasmonic acid (JA) pathways were involved in tomato plant defense responses. The relative gene expressions of PR1 and phenylalanine ammonia lyase (PAL), which are involved in the SA and JA pathways, respectively, were improved in treated plants compared to the control.ConclusionThe findings indicated that algal-induced ToMV resistance was mediated via several defense pathways in tomato. The antiviral mechanism was described, which provides a light on the potential of algae in plant viral disease management.