Cucumber Mosaic Virus Disease Research Articles

Evaluation of Pumpkin Cultivars against Cucumber Mosaic Virus Disease under Field Condition

The family Cucurbitaceae includes pumpkin (Cucurbita moschata Duch.), one of the most significant vegetable crops cultivated both in India and overseas. Various biotic and abiotic factors affect pumpkin production, and one of the biggest threats to its cultivation is the cucumber mosaic virus disease. An experiment was conducted in the experimental field of the Department of Plant Pathology, Biswanath College of Agriculture, Assam Agricultural University, Assam during 2022–2023 with the aim of screening out various varieties of pumpkin and identifying the one that was most resistant to cucumber mosaic virus in view of the disease's significance. Out of eighteen pumpkin cultivars evaluated against cucumber mosaic virus disease, six were moderately susceptible, eleven were susceptible and one cultivar was observed to be highly resistant against the disease.

Expression of defense responsive genes in tripartite interaction of cucumber mosaic virus and plant growth promoting rhizobacteria in ridge gourd (Luffa acutangula (L.) Roxb)

The mosaic caused by cucumber mosaic virus (CMV) on ridge gourd (Luffa acutangula (L.) Roxb) is an important disease. An attempt was made to use a consortium of plant growth promoting rhizobacteria to manage the disease with an aim to reduce the usage of pesticide to control its vector. Eleven isolates of Bacillus spp. were selected based on their plant gowth promotion ability on ridge gourd cv. COH1. Among these, Bacillus pumilus (BSC 4), B. subtilis (Bbv 57) and B. subtilis (BST 8) had shown their potentiality in reducing the severity of CMV disease under artificial conditions. The compatibility test showed that these isolates were compatible to each other. A Bacillus consortium was prepared and evaluated for its efficacy against CMV on ridge gourd and the results showed a reduction of 49.98 % in disease severity over control. The quantitative gene expression analysis revealed that the defense genes viz., peroxidase, polyphenol oxidase, catalase and super oxide dismutase were upregulated in consortium treated ridge gourd plants. The upregulation of these genes indicated the activation of defense pathways which witnessed the induction of systemic resistance in Bacillus consortium treated plants. All gene expressions were reached its peak nearly two to three fold in the consortium treated plants except catalase, its peak expression was found in salicylic acid treated plants which served as a positive control. Correspondingly, the quantitative enzymatic analysis of these defense enzymes at different time intervals was also reflected in similar manner. The elevated level of defense enzymes in plant growth promoting rhizobacteria consortium treated plants was the evident for the onset of systemic resistance.

Chitosan oligosaccharide as a plant immune inducer on the Passiflora spp. (passion fruit) CMV disease.

Cucumber mosaic virus (CMV), one of the main viruses, is responsible for Passiflora spp. (passion fruit) virus diseases, which negatively affect its planting, cultivation, and commercial quality. In this study, a laboratory anti-CMV activity screening model for Passiflora spp. CMV disease was first established. Then, the effects of different antiviral agents of chitosan oligosaccharide (COS), dufulin (DFL), and ningnanmycin (Ning) on CMV virulence rate in Passiflora spp. were determined. The virulence rate and anti-CMV activity in Passiflora spp. treated with COS were 50% and 45.48%, respectively, which were even better than those of DFL (66.67% and 27.30%, respectively) and Ning (83.30% and 9.17%, respectively). Field trials test results showed COS revealed better average control efficiency (47.35%) against Passiflora spp. CMV disease than those of DFL (40.93%) and Ning (33.82%), indicating that COS is effective in the control of the Passiflora spp. CMV disease. Meanwhile, the nutritional quality test results showed that COS could increase the contents of soluble solids, titratable acids, vitamin C, and soluble proteins in Passiflora spp. fruits as well as enhance the polyphenol oxidase (PPO), superoxide dismutase (SOD), and peroxidase (POD) activity in the leaves of Passiflora spp. seedlings. In addition, the combined transcriptome and proteome analysis results showed that COS mainly acted on the Brassinosteroids (BRs) cell signaling pathway, one of plant hormone signal transduction pathway, in Passiflora spp., thus activating the up-regulated expression of TCH4 and CYCD3 genes to improve the resistance to CMV disease. Therefore, our study results demonstrated that COS could be used as a potential plant immune inducer to control the Passiflora spp. CMV disease in the future.

Impact of Beauveria bassiana and Metarhizium anisopliae on the Metabolic Interactions between Cucumber (Cucumis sativus L.) and Cucumber Mosaic Virus (CMV)

In natural systems, plant–endophyte interactions are important for reducing abiotic and biotic stresses in plants by producing a variety of metabolites that protect plants from pathogens and herbivores. Biocontrol strategies are increasingly being used as a viable alternative to chemical pesticides. Entomopathogenic fungi (EPF) are one of them, and they have been touted as a successful method for biological pest control in plants. Because EPF strains are sensitive to environmental conditions when sprayed, the recently discovered endophytic behavior of several EPF strains has improved their management. Cucumber mosaic virus (CMV) is one of the most common and serious plant viruses worldwide, infecting over 1200 plant species and being spread by more than 80 aphid species. CMV control is directed towards the use of chemical insecticides to eradicate its insect vectors. Endophytic EPF is currently being studied to control plant virus infection, and antagonistic effects have been reported. Metabolomics is an emerging research field for plant metabolite profiling and is employed to study plant–endophyte interactions. In the present research, metabolomics approaches were conducted to gain information into mechanisms involved in defense against CMV in endophytes Beauveria bassiana and Metarhizium anisopliae (EPF)-treated diseased cucumber plants. In addition, CMV-induced metabolic changes in cucumber plants were investigated. Our analysis indicated large differences in cucumber metabolites due to endophytes application. In total, six hundred and thirty-one metabolites were differentially expressed in endophyte-treated CMV diseased cucumber plants. Regulation of different kinds of amino acids, organic acids, and phenylpropanoids metabolites could provide insight about plant defense mechanism against CMV pathogen. Important metabolites were found to be regulated in diseased cucumber plants due to fungal endophytes treatment that could possibly confer tolerance to CMV disease.

Effects of Cucumber Mosaic Virus on Yield Components and Yield of Bambara Groundnut

Bambara groundnut (Vigna subterranean L. Verdc) is a leguminous plant and its seeds are highly nutritious and can be considered as complete food. In addition to being a neglected crop; its production is limited by several constraints among which virus diseases are the most implicated. In order to contribute to the improvement of bambara groundnut in Nigeria, landraces of bambara groundnut were screened for resistance to Cucumber mosaic virus (CMV), one of the most damaging viruses in grain legumes. Treatments consisted of five landraces namely Black, Brown, Cream, Red nav, and Zebra coloured got from local farmers. These were arranged in Randomised Complete Block Design, with three replicates. Seedlings were infected with CMV isolate three weeks after sowing (WAS), during the 2019 and 2020 trials. The infected plants exhibited various symptoms of chlorosis, leaf deformation, growth retardation, and plant stunting. The sCMV caused significant reduction in plant height, the number of branches, leaves, pods, and seeds weight. In the 2019 and 2020 trials, 100 % incidence with the highest severity was observed in the Bambara groundnut landraces. Disease incidence varied between 41.6% in “Black” and 95.8 % in “Cream,” while disease severity was higher in “Cream” and “Red nav” with 5.0 respectively. “Black” and “Zebra” were the tallest with 16.8 cm among the infected as well as disease-free with 22.6 cm tall plants. “Black” landrace produced the highest number of pods in both CMV infections with 21 and disease-free with 33 pods respectively. Conversely, the number of days to flowering of 43 days was highest in infected plants of “Black”. The “Black” and “Zebra” landraces recorded uniform seed weights and the highest seed weight under CMV infection with 1.7 g per plant. The impact of the virus on yield loss was lowest in “Black” and “Zebra” landraces which indicated their possible use in the management of Cucumber mosaic virus disease in Bambara groundnut.

Spatio-temporal analysis of cucumber mosaic virus disease and its sustainable management

Spatio-temporal analysis of cucumber mosaic virus disease and its sustainable management

Salicylic acid and the viral virulence factor 2b regulate the divergent roles of autophagy during cucumber mosaic virus infection

ABSTRACT Macroautophagy/autophagy is a conserved intracellular degradation pathway that has recently emerged as an integral part of plant responses to virus infection. The known mechanisms of autophagy range from the selective degradation of viral components to a more general attenuation of disease symptoms. In addition, several viruses are able to manipulate the autophagy machinery and counteract autophagy-dependent resistance. Despite these findings, the complex interplay of autophagy activities, viral pathogenicity factors, and host defense pathways in disease development remains poorly understood. In the current study, we analyzed the interaction between autophagy and cucumber mosaic virus (CMV) in Arabidopsis thaliana. We show that autophagy is induced during CMV infection and promotes the turnover of the major virulence protein and RNA silencing suppressor 2b. Intriguingly, autophagy induction is mediated by salicylic acid (SA) and dampened by the CMV virulence factor 2b. In accordance with 2b degradation, we found that autophagy provides resistance against CMV by reducing viral RNA accumulation in an RNA silencing-dependent manner. Moreover, autophagy and RNA silencing attenuate while SA promotes CMV disease symptoms, and epistasis analysis suggests that autophagy-dependent disease and resistance are uncoupled. We propose that autophagy counteracts CMV virulence via both 2b degradation and reduced SA-responses, thereby increasing plant fitness with the viral trade-off arising from increased RNA silencing-mediated resistance.

Computational investigation of phytoalexins as potential antiviral RAP-1 and RAP-2 (Replication Associated Proteins) inhibitor for the management of cucumber mosaic virus (CMV): a molecular modeling, in silico docking and MM-GBSA study

The Replication Associated Proteins (RAP-1 and RAP-2) encoded by CMV ORF 1a and ORF 2a are required for the different stages of the viral replication cycle; being multi-functional, they are good inhibitory targets for anti-CMV compounds. As a new perspective for sustainable crop improvement, we investigated the natural plant-based antimicrobial phytoalexins for their anti-CMV potential. Here, we modeled and predicted the functional domains of RAP-1 and RAP-2, docked with a ligand library comprising 128 phytoalexins reported with broad-spectrum activity, determined their binding energies (BEs), molecular interactions, and inhibition constant (Ki), and compared with the reference plant antiviral compounds ribavirin, ningnanmycin, and benzothiadiazole (BTH). Further, the change in Gibb’s free energy of binding (ΔG) and the per residue contribution of the selected top-scored ligand molecules was assessed by the prime MM-GBSA approach. Our results revealed RAP-1 as a discontinuous two-domain and RAP-2 as a multi-domain protein. The compounds glyceollidin (9.8 kcal/mol) and moracin D (7.8 kcal/mol) topped the list for RAP-1 and RAP-2 protein targets respectively and also, the lead molecules had energetically more favorable and comparative ΔG values than the top-scored plant antiviral agent ningnanmycin. The evaluation of in vitro toxicity and agrochemical-like properties showed the least toxicity of these anti-CMV compounds. Taken together, our results provide new insights in understanding the inhibitory effects of phytoalexins towards the RAP proteins and could be employed as new promising anti-CMV candidate compounds for their application in agriculture as biopesticides to combat the CMV disease incidence. Communicated by Ramaswamy H. Sarma

Susceptibility of ten pepper breeding lines to cucumber mosaic virus disease

Pepper (Capsicum annuum) is a major vegetable of global importance. Its production is however affected by varying biotic and abiotic stresses. Virus infections possess a genuine danger to pepper cultivation in Nigeria and all over the world resulting in over 50 % yield losses. Thus, the need to subject available pepper germplasm to screening against virus diseases for possible identification of resistant genes which may be used in breeding programmes to obtain improved lines that are high yielding. This study was undertaken to evaluate the growth and performances of ten pepper breeding lines under cucumber mosaic virus disease. The experiment was laid out in completely randomised design with five replications. Ten pepper breeding lines were evaluated as healthy and inoculated with cucumber mosaic virus and evaluated for their responses. Data were recorded for disease incidence, severity, growth and yield attributes. The data were subjected to analysis of variance. The results revealed that NHPK/D6-1-1 which showed mild disease incidence (36.7 % on average) with an average severity (score = 2.2), produced the highest number of leaves per plant (13) and branches (8) under diseased condition was the least vulnerable. The CMV-infected breeding lines were fruitless except for NHPK/D6-1-1 and NHPK/21-4-1-2 which produced an average of 2 fruits per plant. The selection of NHPK/D6-1-1 and NHPK/21-4-1-2 for further evaluation is therefore recommended for possible CMV-tolerant genes. The identification of virus-resistant breeding lines would provide more effective control of virus diseases in pepper production.
 Keywords: Capsicum annuum; Cucumber mosaic virus; Breeding lines; NHPK

Transcriptome analysis of Luffa cylindrica (L.) Roem response to infection with Cucumber mosaic virus (CMV)

Cucumber mosaic virus (CMV) can cause serious losses in Luffa cylindrica (L.) Roem. Chemical application to control CMV is ineffective and environmentally unfriendly. The development of resistant hybrids is the best way to control CMV disease. Elucidating the virus-host interaction of CMV and molecular basis underlying Luffa spp. resistance against CMV would undoubtedly facilitate breeding for resistance against CMV disease. Transcriptome sequencing was used to analyze differentially expressed genes (DEGs) caused by CMV infection. A total of 138,336 unigenes were assembled, and 74,525 unigenes were annotated. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that the three major enrichment pathways (according to the p-values) were flavonoid biosynthesis, sulfur metabolism, and photosynthesis. Genes involved in basal defenses, probably R genes, were determined to be related to CMV resistance. Using quantitative real-time PCR, we validated the differential expression of 8 genes. A number of genes associated with CMV resistance were found in this study. This study provides transcriptomic information regarding CMV-Luffa spp. interactions and will shed light on our understanding of host-virus interactions.

Biological confirmation of resistance from segregating populations of Gherkin (Cucumis anguria L.) against cucumber mosaic virus (CMV)

Cucumber Mosaic Virus (CMV) is most widespread and destructive disease of gherkin (Cucumis anguria L.) Most of the commercial varieties are susceptible to CMV disease. Thus, identification of resistant genotypes for management of CMV disease in gherkin is essential. A total of 179 F3 progenies derived from crosses of resistant and susceptible parent’s viz., Acc.1 (susceptible) x Acc. 50 (resistant), Acc.3 (susceptible) x Acc.50 (resistant), Acc.48 (susceptible) x Acc 50 (resistant) were screened for CMV. Among 179 F3 families, 7 were Immune, 17 were Resistant, 76 were Moderately Resistant, 73 were Moderately Susceptible and 6 were Susceptible. The immune and resistant progenies were further confirmed for their resistance reaction by aphid transmission. Significant difference between the estimates of PDI or F3 progenies mapped into different response classes justified the classification.

Reactions of commercial cultivars of okra, pepper, and tomato to cucumber mosaic virus disease

Okra ( Abelmoschus esculentus ), pepper ( Capsicum spp.) and tomato ( Solanum lycopersicum ) are rich sources of minerals and vitamins required by humans for normal growth and development. However, the productivity of these vegetables is seriously constrained by Cucumber mosaic virus (CMV) disease. To date, adoption of resistant cultivars is the most effective, ecologically sound and sustainable management strategy against the disease. Therefore, selected cultivars of okra (Clemson Spineless, Ex Bassawa -2 and NHAe 47 - 4), pepper (California Wonder, Cayenne and Yolo Wonder) and tomato (Roma Savanna, Tropimech, and UC82B) were evaluated for resistance to CMV. The experiment was conducted under screenhouse and field conditions in Minna, Southern Guinea Savanna zone of Nigeria. Completely randomised design with six replications was used in screenhouse while the field trial was laid out using randomised complete block design with three replications. Seedlings were inoculated with CMV at 10 days after emergence. Disease incidence, disease severity, growth and yield characteristics were recorded. Data were subjected to analysis of variance at p ≤ 0.05. Infected plants elicited mosaic symptoms but disease severity was cultivar dependent. Plant height, leaf area, fruit length, fruit diameter and fruit weight were all reduced by CMV. The lowest disease incidence ( < 35 %), severity ( < 3), reductions in morphological and yield parameters ( < 10 %) were found in Ex- Bassawa-2, Cayenne, and Roma Savanna. This indicated that they contained CMV tolerant genes. Therefore, the three most tolerant cultivars (Ex- Bassawa-2 cultivar of okra, Cayenne of pepper and Roma Savanna of tomato) are recommended to farmers in CMV prone areas. Keywords: CMV; Disease incidence; Growth and yield; Severity; Vegetables

STUDIES ON SWEET BASIL MOSAIC VIRUS DISEASE AND ITS CONTROL BY USING SOME ESSENTIAL OILS

The current study, the mosaic virus disease of Ocimum basilicum L. (sweet basil) was identified and the different effects of three essential oils on growth, oil content and composition as well as reducing CMV disease symptoms of sweet basil plants in vivo. During 2012 season, natural occurrence of mosaic virus disease was observed on sweet basil in Assiut, Egypt. The causal agent of basil mosaic disease was detected as cucumber mosaic virus (CMV) by PCR product that revealed presence of approximately expected size (~ 781 bp) in naturally infected basil. Therefore, a field experiment was carried out during two successive seasons 2013 and 2014 on sweet basil plants at the Experimental Farm of Arab El Awamer Agricultural Research Station, Assiut Governorate, Egypt. Ten treatments of three essential oils extracted from lemongrass (Cymbopogon citratus), rosemary (Rosemarinus officinalis) and peppermint (Mentha piperita L.) plants were applied as foliar spray at 1% concentration before and after inoculation with isolated virus and two controls (healthy and infected plants) were arranged in a randomized complete block design with three replicates. Results revealed that application of essential oils under field condition improved growth and yield (branches, weight of fresh and dry plant (g/plant) as well as essential oil percentage), reduced the CMV disease symptoms compared to untreated infected control. As well as significant increase in total identified of essential oil composition of basil plant. Whereas the treatment with rosemary oil before and after inoculation respectively, was increased in myrcene, linalool when applied before inoculation and with a great increase in 1, 8-cineole when applied after inoculation. Also a great increase was related to peppermint oil treatment for eugenol, myrcene and 1, 8-cineole % before inoculation comparable to untreated infected plants. While, using of peppermint oil significantlyincreased number of branches, fresh and dry weights, essential oil content and composition when applied before inoculation with virus compared to infected and healthy controls. Lemongrass essential oils exhibited a moderate protective effects. Generally, applying of rosemary essential oil as curative seemed to be superior for improving branches, weight of fresh and dry plant (g/plant), and essential oil percentage and composition comparing to other treatments.

Effect of Pyraclostrobin Application on Viral and Bacterial Diseases of Tomato.

Quinone outside inhibitors (QoI) are powerful fungicides, which have been reported, additionally to their fungicide activity, to increase plant capacity to activate cellular defense responses and to promote plant growth. In this work, the effect of the QoI class fungicide pyraclostrobin was examined against Cucumber mosaic virus (CMV), Potato virus Y (PVY) and Pseudomonas syringae pv. tomato in tomato plants following artificial inoculation of the plants with the pathogens. Under controlled environmental conditions, pyraclostrobin delayed viral and bacterial disease development, even if P. syringae pv. tomato internal population levels were not affected significantly. In contrast, under field conditions in commercial greenhouses, a reduced CMV disease incidence throughout the tomato cultivation period was recorded. Gene expression analysis indicated an effect of pyraclostrobin application on tomato MAPKs transcript levels and a possible interference with plant stress responses.

Performance of Two Locally Adapted Okra Varieties as Influenced by Cucumber Mosaic Virus Disease

The responses of two locally adapted okra varieties (Bokungi and Ikeregi) to Cucumber mosaic virus (CMV) were evaluated under field conditions during the 2014 cropping season. Seedlings were inoculated with the virus at 1 week after emergence. Each genotype was evaluated as inoculated and uninoculated treatments. Disease incidence, severity of infection (scale 1 – 5), yield and yield related parameters were measured. Virus titre was quantified using Enzyme-Linked Immunosorbent Assay (ELISA). Data were subjected to independent t test and significance was determined at 5 % level of probability. One hundred percent infection was found in both varieties but disease severity was higher in “Bokungi” (5) than in “Ikeregi” (3). Higher virus concentration was found in the inoculated leaves of “Bokungi“(ELISA value = 0.89) compared to “Ikeregi” (ELISA value = 0.41). Reductions in plant height (8.8 %), fruit number (33.3 %) and fruit weight (37.6 %) were significantly lower in “Ikeregi” than “Bokungi”. The present data reveal that both okra varieties are susceptible to CMV infection but “Ikeregi” appears to be more tolerant. Cultivation of the more CMV-tolerant okra variety would offer some level of insurance against complete crop failure in case of disease outbreak in the study area.Keywords: Cucumber mosaic virus, disease severity, resistance, yield, okra

VIRAL SATELLITE RNA AS A BIOLOGICAL CONTROL AGENT FOR PLANTS

Biological control technology based on viral satellite mediated protection is a novel concept of the viral disease control strategies. Cucumber mosaic virus (CMV) is considered one of the most economically damaging viruses among field grown vegetables such as tomato (Solanum lycopersicum L). CMV can harbor molecular parasites known as satellite RNAs that dramatically alter the symptom phenotype induced by the virus. Two indigenous strains of CMV satellite RNA were isolated and have been sequenced. One of these strains designated as CMV‐KU1 reduced the viral disease to a virtually asymptomatic condition. The other strain was found to aggravate the symptoms and cause severe crop loss and tomato necrosis. Thus, satellites have been referred to as “natural inhibitors of crop damaging viruses’. These satellites RNAs are small nucleic acids whose nucleotide sequences are unrelated to, but are replicatively dependent upon the viral genome; they have a molecular parasitic relationship. Particularly, the KU1 strain may be used to protect plants against a particular viral strain of CMV, referred to as the KU2 strain. The attenuating properties of some satellite RNAs can be exploited to control viral diseases by preinoculating crops with an attenuating satellite RNA variant combined with virus. This technique can effectively protect against CMV disease in the field.

Benzothiadiazole-elicited defense priming and systemic acquired resistance against bacterial and viral pathogens of pepper under field conditions

Like the innate immunity in mammals, plants have developed an induced resistance, referred to as systemic acquired resistance (SAR). Recently, defense priming that is not related to the direct activation of defenses, but instead elicits more rapid induction of resistance mechanisms following trigger application, has been proposed to explain the long-lasting effect of SAR. However, the majority of previous studies have focused on understanding the molecular mechanism underlying priming under in vitro and laboratory conditions. This study examined whether defense priming occurred and was detectable with SAR marker genes by a chemical elicitor, benzothiadiazole (BTH), under field conditions. Pepper seedling application of 0.5 mM BTH was sufficient to prime the CaPR4 gene for 20 days as well as to induce SAR against bacterial spot caused by Xanthomonas axonopodis. Transcriptome analysis revealed to prime defense hormonal signaling and antimicrobial compound production genes. At the end of the season, when bacterial spot and Cucumber mosaic virus disease outbreaks naturally occurred, BTH-treated plants demonstrated less disease symptoms. Our results indicate that the priming of SAR genes plays a critical role in plant protection against pathogens under natural conditions.

Cucumber mosaic virus: viral genes as virulence determinants

Cucumber mosaic virus (CMV) is the type species of the genus Cucumovirus in the family Bromoviridae, which also encompasses the Peanut stunt virus (PSV) and the Tomato aspermy virus (TAV). Nucleotide sequence similarity among these three cucumoviruses is 60%-65%. CMV strains are divided into three subgroups, IA, IB and II, based on the sequence of the 5' untranslated region of the genomic RNA 3. Overall nucleotide sequence similarity among CMV strains is approximately 70%-98%. GEOGRAPHICAL DISTRIBUTION, HOST RANGE AND SYMPTOMATOLOGY: CMV is distributed worldwide, primarily in temperate to tropical climate zones. CMV infects more than 1200 species of 100 plant families, including monocot and dicot plants. Symptoms caused by CMV infection vary with the host species and/or CMV strain, and include mosaic, stunt, chlorosis, dwarfing, leaf malformation and systemic necrosis. CMV disease is spread primarily by aphid transmission in a nonpersistent manner. In tobacco sap, the thermal inactivation point of the viral infectivity is approximately 70 °C (10 min), the dilution end-point is approximately 10(-4) and viral infectivity is lost after a few days of exposure to 20 °C. Viral infectivity can be retained in freeze-dried tissues and in the form of virions purified using 5 mm sodium borate, 0.5 mm ethylenediaminetetraacetic acid and 50% glycerol (pH 9.0) at -20 °C. CMV particles are isometric, approximately 28-30 nm in diameter and are composed of 180 capsid subunits arranged in pentamer-hexamer clusters with T= 3 symmetry. The sedimentation coefficient (s(20) ,(w) ) is c. 98 S and the particle weight is (5.8-6.7) × 10(6) Da. The virions contain 18% RNA. The RNA-protein interactions that stabilize the CMV virions are readily disrupted by sodium dodecylsulphate or neutral chloride salts. GENOMIC PROPERTIES: The genomic RNAs are single-stranded messenger sense RNAs with 5' cap and 3' tRNA-like structures containing at least five open reading frames. The viral RNA consists of three genomic RNAs, RNA 1 (c. 3.3 kb), RNA 2 (c. 3.0 kb) and RNA 3 (c. 2.2 kb), and two subgenomic RNAs, RNA 4 (c. 1.0 kb) and RNA 4A (c. 0.7 kb). The 3' untranslated regions are conserved across all viral RNAs. CMV is often accompanied by satellite, noncoding, small, linear RNA that is nonhomologous to the helper CMV.

Virus symptom expressions on Musa landraces in 1999, 2000 and 2004 in southern Nigeria: Cucumber mosaic virus (CMV) disease incidence and subgroup differentiation

Musa landraces (469) from 73 villages in 10 states in 1999, 2000 and 2004 in southern Nigeria were visually assessed to determine virus symptoms associated with CMV disease. CMV indexing was done using dot-blot immunoassay and ELISA. Monoclonal antibodies were used to group CMV isolates in 2004. Symptoms of interveinal chlorosis and chlorotic streaks were observed in 22.4 and 17.9% of the Musa samples with CMV disease incidences of 17.1% and 14.7%, respectively. Other virus symptoms accounted for between 1.5 and 12.2% of the total leaf samples while 13.9% were asymptomatic. CMV incidence in asymptomatic leaf samples was as high as 10.4% while the virus incidence in the other symptom types were between 0.9 and 7.9%. The incidences of CMV in both the symptomatic and asymptomatic plants in 1999, 2000 and 2004 were between 1.3 and 18.7%, 1.9 and 26.9% and 4.9 and 26.4%, respectively.

Rhizobacteria-Mediated Growth Promotion of Tomato Leads to Protection AgainstCucumber mosaic virus

ABSTRACT We evaluated combinations of two strains of plant growth-promoting rhizobacteria (PGPR) formulated with the carrier chitosan for the ability to induce growth promotion of tomato plants and resistance to infection by Cucumber mosaic virus (CMV). Each PGPR combination included GB03 (Bacillus subtilis) and one of the following PGPR strains: SE34 (B. pumilus), IN937a (B. amyloliquefaciens), IN937b (B. subtilis), INR7 (B. pumilus), or T4 (B. pumilus). The PGPR combinations formulated with chitosan are referred to as biopreparations. Tomato plants treated with each of the biopreparations appeared phenotypically and developmentally similar to nonbacterized control plants that were 10 days older (referred to as the older control). When plants were challenged with CMV, all plants in the biopreparation treatments and the older control treatment had significantly greater height, fresh weight, and flower and fruit numbers than that of plants in the CMV-inoculated same age control treatment. CMV disease severity ratings were significantly lower for biopreparation-treated and older control tomato plants than for that of same age control plants at 14 and 28 days postinoculation (dpi). CMV accumulation in young noninoculated leaves was significantly less for all biopreparation-treated plants and those in the older control than for the same age control plants at 14 dpi and for four of the five biopreparation treatments at 28 dpi. In those tomato plants shown to be infected, the amount of CMV in noninoculated leaves was significantly lower for three of the biopreparation treatments and the older control treatment at 14 dpi and biopreparation G/INR7 treatment at 28 dpi when compared with the control treatment. These data show that treatment of tomato plants with biopreparations results in significant enhancement of growth and protection against infection by CMV.