Human adenovirus-associated health risk in the recreational waters of the Yal-ku lagoon in the Mexican Caribbean.

The study objective was to evaluate human faecal contamination impacts in the Yal-ku lagoon in the Mexican Caribbean and to estimate adenovirus infection and illness risks associated with recreational exposure during water activities. A total of 20 water samples (10 from each site × two sites) (50 L) were collected monthly over a period of 12 months from two selected sampling sites in the swimming area of the Yal-ku lagoon. The occurrence of faecal-associated viruses was explored, and human adenovirus (HAdV) and pepper mild mottle virus (PMMoV) concentrations were quantified. A quantitative microbial risk assessment (QMRA) model was used to estimate exposure and subsequent adenovirus infection and illness risk for 1 h of swimming or snorkelling. Somatic and F + -specific coliphages occurred in 100% of the samples. Both HAdV and PMMoV were detected at a 60% frequency thereby indicating persistent faecal inputs. PMMoV concentrations (44-370 GC/L) were relatively lower than the concentrations of HAdV (64-1,000 GC/L). Estimated mean adenovirus risks were greater for snorkelling than for swimming by roughly one to two orders of magnitude and estimated mean illness risks for snorkelling were >32/1,000. Human faecal contamination is frequent in the Yal-ku lagoon, which is associated with human gastrointestinal illness.

Variability in indigenous Pakistani tomato lines and worldwide reference collection for Tomato Mosaic Virus (ToMV) and Tomato Yellow Leaf Curl Virus (TYLCV) infection.

Local and exotic germplasm of tomato remains a major source for genetic improvement. Assessment of such lines for biotic stresses particularly viral diseases are the most important criteria for selection in Pakistan, where Tomato Yellow Leaf Curl Virus (TYLCV) and Tomato Mosaic Virus (ToMV) are the major diseases/viruses. A set of 40 accessions (including indigenous Pakistani lines and exotic germplasm from Europe, the United States, and Asia) were evaluated for their resistance/infection response to ToMV with artificial inoculation under greenhouse conditions. Infection response was quantified through disease scoring and DAS-ELISA test (for ToMV). A subset of 24 lines, was further screened for TYLCV using disease scoring and TAS-ELISA. The tested lines showed significant variability for resistance to ToMV. Only one accession (Acc-17878) was resistant to the ToMV whereas seven accessions i.e. Acc-17890, AVR-261, CLN-312, AVR-321, EUR-333, CLN-352, and CLN-362 expressed resistance to TYLCV. Correlation between phenotypic evaluation was confirmed by the ELISA results in both diseases, although both tools complemented to assess the viral infection status. In future, tomato breeding programs must consider breeding for ToMV and TYLCV resistance (using identified germplasm in our study) so as to deliver virus resistant tomato varieties.

Development of a droplet digital polymerase chain reaction (ddPCR) assay for the detection of Tomato brown rugose fruit virus (ToBRFV) in tomato and pepper seeds.

In the present study, a droplet digital PCR assay was developed for detection of Tomato brown rugose fruit virus, a new Tobamovirus of tomato and other solanaceous plants, which expands the diagnostic strategies for this pathogen. Candidate reference DNA material was also obtained to be employed as positive control in tomato and pepper samples. Recombinant plasmids encode for ToBRFV coat protein (CP-ToBRFV) gene and Solanum lycopersicum GAPDH fragments, and CP-ToBRFV and Capsicum annuum GAPDH. To our knowledge, this is the first report of ToBRFV detection in tomato and pepper seeds using ddPCR.

Tobamoviruses of two new species trigger resistance in pepper plants harbouring functional L alleles.

Tobamoviruses are often referred to as the most notorious viral pathogens of pepper crops. These viruses are not transmitted by invertebrate vectors, but rather by physical contact and seeds. In this study, pepper plants displaying mild mottle and mosaic symptoms were sampled in four different regions of Peru. Upon double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) tests, seven samples cross-reacted weakly with antibodies against pepper mild mottle virus (PMMoV), suggesting the presence of tobamoviruses. When employing RT-PCR, conserved primers amplified cDNA fragments of viruses from two putative new tobamovirus species in the samples. The complete genome of two representative isolates were, therefore, sequenced and analysed in silico. These viruses, which were tentatively named yellow pepper mild mottle virus (YPMMoV) and chilli pepper mild mottle virus (CPMMoV), shared highest nucleotide genome sequence identities of 83 and 85 % with bell pepper mottle virus (BpeMV), respectively. Mechanical inoculation of indicator plants with YPMMoV and CPMMoV isolates did not show any obvious differences in host ranges. These viruses were also inoculated mechanically on pepper plants harbouring different resistance L alleles to determine their pathotypes. Pepper plants carrying unfunctional L alleles (L0) to tobamoviruses were infected by all isolates and presented differential symptomatology for YPMMoV and CPMMoV. On the other hand, pepper plants carrying L1, L2, L3 and L4 alleles were resistant to all isolates, indicating that these viruses belong to pathotype P0.

siRNA biogenesis and advances in topically applied dsRNA for controlling virus infections in tomato plants.

A non-transgenic approach based on RNA interference was employed to induce protection against tomato mosaic virus (ToMV) infection in tomato plants. dsRNA molecules targeting the cp gene of ToMV were topically applied on plants prior to virus inoculation. Protection was dose-dependent and sequence-specific. While no protection was achieved when 0-16 µg dsRNA were used, maximum rates of resistance (60 and 63%) were observed in doses of 200 and 400 µg/plant, respectively. Similar rates were also obtained against potato virus Y when targeting its cp gene. The protection was quickly activated upon dsRNA application and lasted for up to 4 days. In contrast, no detectable antiviral response was triggered by the dsRNA from a begomovirus genome, suggesting the method is not effective against phloem-limited DNA viruses. Deep sequencing was performed to analyze the biogenesis of siRNA populations. Although long-dsRNA remained in the treated leaves for at least 10 days, its systemic movement was not observed. Conversely, dsRNA-derived siRNA populations (mainly 21- and 22-nt) were detected in non-treated leaves, which indicates endogenous processing and transport through the plant. Altogether, this study provides critical information for the development of novel tools against plant viruses; strengths and limitations inherent to the systems are discussed.

Tobamoviruses can be frequently present in the oropharynx and gut of infants during their first year of life.

Plant viruses have been reported to be common in the gut of human adults, presumably as result of food ingestion. In this work, we report that plant viruses can also be found frequently in the gut and oropharynx of children during their first year of life, even when they are exclusively breast-fed. Fecal and oropharynx samples were collected monthly, from birth to 1 year of age, from three apparently healthy children in a semi-rural community and analyzed by next generation sequencing. In 100% of the fecal samples and 65% of the oropharynx samples at least one plant virus was identified. Tobamoviruses in the Virgaviridae family were by far the most frequently detected, with tropical soda apple mosaic virus, pepper mild mottle virus, and opuntia tobamovirus 2 being the most common species. Seventeen complete virus genomes could be assembled, and phylogenetic analyses showed a large diversity of virus strains circulating in the population. These results suggest that children are continuously exposed to an extensive and highly diverse collection of tobamoviruses. Whether the common presence of plant viruses at an early age influences the infant's immune system, either directly or through interaction with other members of the microbiota, remains to be investigated.

RdDM pathway components differentially modulate Tobamovirus symptom development.

KEY MESSAGE: The crop yield losses induced by phytoviruses are mainly associated with the symptoms of the disease. DNA modifications as methylation can modulate the information coded by the sequence, process named epigenetics. Viral infection can change the expression patterns of different genes linked to defenses and symptoms. This work represents the initial step to expose the role of epigenetic process, in the production of symptoms associated with plants-virus interactions. Small RNAs (sRNAs) are important molecules for gene regulation in plants and play an essential role in plant-pathogen interactions. Researchers have evaluated the relationship between viral infections as well as the endogenous accumulation of sRNAs and the transcriptional changes associated with the production of symptoms, but little is known about a possible direct role of epigenetics, mediated by 24-nt sRNAs, in the induction of these symptoms. Using different RNA directed DNA methylation (RdDM) pathway mutants and a triple demethylase mutant; here we demonstrate that the disruption of RdDM pathway during viral infection produce alterations in the plant transcriptome and in consequence changes in plant symptoms. This study represents the initial step in exposing that DNA methylation directed by endogenous sRNAs has an important role, uncoupled to defense, in the production of symptoms associated with plant-virus interactions.

Identification and genomic characterization of a novel tobamovirus from prickly pear cactus.

In this work, we describe the complete sequence and genome organization of a novel tobamovirus detected in a prickly pear plant (Opuntia sp.) by high-throughput sequencing, tentatively named "opuntia virus 2". The full genome of opuntia virus 2 is 6,453 nucleotides in length and contains four open reading frames (ORFs) coding for the two subunits of the RNA polymerase, the movement protein, and the coat protein, respectively. Phylogenetic analysis using the complete nucleotide sequence revealed that the virus belongs to the genus Tobamovirus (family Virgaviridae), showing the highest nucleotide sequence identity (49.8%) with cactus mild mottle virus (CMMoV), being indicating that it belongs in the Cactaceae subgroup of tobamoviruses.

Development of a new tobamovirus-based viral vector for protein expression in plants.

Plants are becoming an interesting alternative system for the heterologous production of pharmaceutical proteins, providing a more scalable, cost-effective, and biologically safer option than the current expression systems. The development of plant virus expression vectors has allowed rapid and high-level transient expression of recombinant genes, and, in turn, provided an attractive plant-based production platform. Here we report the development of vectors based on the tobamovirus Pepper mild mottle virus (PMMoV) to be used in transient expression of foreign genes. In this PMMoV vector, a middle part of the viral coat protein gene was replaced by the green fluorescent protein (GFP) gene, and this recombinant genome was assembled in a binary vector suitable for plant agroinoculation. The accumulation of GFP was evaluated by observation of green fluorescent signals under UV light and by western blotting. Furthermore, by using this vector, the multiepitope gene for chikungunya virus was successfully expressed and confirmed by western blotting. This PMMoV-based vector represents an alternative system for a high-level production of heterologous protein in plants.

Occurrence of Pepper Mild Mottle Virus (PMMoV) in Groundwater from a Karst Aquifer System in the Yucatan Peninsula, Mexico.

The Yucatan Peninsula of Mexico hosts a karst aquifer system that is the only source of freshwater for the area; however, it is vulnerable to human-mediated contamination. Pepper mild mottle virus (PMMoV) is one of the most abundant RNA viruses associated with human feces, making it a viable indicator for tracking fecal pollution in aquatic environments, including groundwater. In this study, groundwater samples collected from a karst aquifer from fresh and brackish water locations were analyzed for fecal indicator bacteria, somatic and male F+ specific coliphages, and PMMoV during the rainy and dry seasons. Total coliform bacteria were detected at all sites, whereas Escherichia coli were found at relatively low levels <40 MPN/100 ml. The highest average concentrations of somatic and male F+ specific coliphages were 920 and 330 plaque forming units per 100 ml, respectively, detected in freshwater during the rainy season. PMMoV RNA was detected in 85% of the samples with gene sequences sharing 99-100% of nucleotide identity with PMMoV sequences available in GenBank. Quantification of PMMoV genome copies (GC) by quantitative real-time PCR indicated concentrations ranging from 1.7 × 101 to 1.0 × 104 GC/L, with the highest number of GC detected during the rainy season. No significant correlation was observed between PMMoV occurrence by season or water type (p > 0.05). Physicochemical and indicator bacteria were not correlated with PMMoV concentrations. The abundance and prevalence of PMMoV in the karst aquifer may reflect its environmental persistence and its potential as a fecal indicator in this karst aquifer system.

The complete genome sequence, occurrence and host range of Tomato mottle mosaic virus Chinese isolate.

BACKGROUND: Tomato mottle mosaic virus (ToMMV) is a recently identified species in the genus Tobamovirus and was first reported from a greenhouse tomato sample collected in Mexico in 2013. In August 2013, ToMMV was detected on peppers (Capsicum spp.) in China. However, little is known about the molecular and biological characteristics of ToMMV. METHODS: Reverse transcription-polymerase chain reaction (RT-PCR) and rapid identification of cDNA ends (RACE) were carried out to obtain the complete genomic sequences of ToMMV. Sap transmission was used to test the host range and pathogenicity of ToMMV. RESULTS: The full-length genomes of two ToMMV isolates infecting peppers in Yunnan Province and Tibet Autonomous Region of China were determined and analyzed. The complete genomic sequences of both ToMMV isolates consisted of 6399 nucleotides and contained four open reading frames (ORFs) encoding 126, 183, 30 and 18 kDa proteins from the 5' to 3' end, respectively. Overall similarities of the ToMMV genome sequence to those of the other tobamoviruses available in GenBank ranged from 49.6% to 84.3%. Phylogenetic analyses of the sequences of full-genome nucleotide and the amino acids of its four proteins confirmed that ToMMV was most closely related to Tomato mosaic virus (ToMV). According to the genetic structure, host of origin and phylogenetic relationships, the available 32 tobamoviruses could be divided into at least eight subgroups based on the host plant family they infect: Solanaceae-, Brassicaceae-, Cactaceae-, Apocynaceae-, Cucurbitaceae-, Malvaceae-, Leguminosae-, and Passifloraceae-infecting subgroups. The detection of ToMMV on some solanaceous, cucurbitaceous, brassicaceous and leguminous plants in Yunnan Province and other few parts of China revealed ToMMV only occurred on peppers so far. However, the host range test results showed ToMMV could infect most of the tested solanaceous and cruciferous plants, and had a high affinity for the solanaceous plants. CONCLUSIONS: The complete nucleotide sequences of two Chinese ToMMV isolates from naturally infected peppers were verified. The tobamoviruses were divided into at least eight subgroups, with ToMMV belonging to the subgroup that infected plants in the Solanaceae. In China, ToMMV only occurred on peppers in the fields till now. ToMMV could infect the plants in family Solanaceae and Cucurbitaceae by sap transmission.

Modulation of host plant immunity by Tobamovirus proteins.

BACKGROUND: To establish successful infection, plant viruses produce profound alterations of host physiology, disturbing unrelated endogenous processes and contributing to the development of disease. In tobamoviruses, emerging evidence suggests that viral-encoded proteins display a great variety of functions beyond the canonical roles required for virus structure and replication. Among these, their modulation of host immunity appears to be relevant in infection progression. SCOPE: In this review, some recently described effects on host plant physiology of Tobacco mosaic virus (TMV)-encoded proteins, namely replicase, movement protein (MP) and coat protein (CP), are summarized. The discussion is focused on the effects of each viral component on the modulation of host defense responses, through mechanisms involving hormonal imbalance, innate immunity modulation and antiviral RNA silencing. These effects are described taking into consideration the differential spatial distribution and temporality of viral proteins during the dynamic process of replication and spread of the virus. CONCLUSION: In discussion of these mechanisms, it is shown that both individual and combined effects of viral-encoded proteins contribute to the development of the pathogenesis process, with the host plant's ability to control infection to some extent potentially advantageous to the invading virus.

Hibiscus latent Fort Pierce virus in Brazil and synthesis of its biologically active full-length cDNA clone.

A Brazilian isolate of Hibiscus latent Fort Pierce virus (HLFPV-BR) was firstly found in a hibiscus plant in Limeira, SP, Brazil. RACE PCR was carried out to obtain the full-length sequences of HLFPV-BR which is 6453 nucleotides and has more than 99.15 % of complete genomic RNA nucleotide sequence identity with that of HLFPV Japanese isolate. The genomic structure of HLFPV-BR is similar to other tobamoviruses. It includes a 5' untranslated region (UTR), followed by open reading frames encoding for a 128-kDa protein and a 188-kDa readthrough protein, a 38-kDa movement protein, 18-kDa coat protein, and a 3' UTR. Interestingly, the unique feature of poly(A) tract is also found within its 3'-UTR. Furthermore, from the total RNA extracted from the local lesions of HLFPV-BR-infected Chenopodium quinoa leaves, a biologically active, full-length cDNA clone encompassing the genome of HLFPV-BR was amplified and placed adjacent to a T7 RNA polymerase promoter. The capped in vitro transcripts from the cloned cDNA were infectious when mechanically inoculated into C. quinoa and Nicotiana benthamiana plants. This is the first report of the presence of an isolate of HLFPV in Brazil and the successful synthesis of a biologically active HLFPV-BR full-length cDNA clone.

Occurrence and molecular characterization of Cucumber green mottle mosaic virus in cucurbit crops of KPK, Pakistan

Field survey of the cucurbit crops revealed a high incidence of Cucumber green mottle mosaic virus (CGMMV) in Khyber Pakhtunkhwa Province (KPK), Pakistan. Among the seven districts surveyed, average percent incidence of CGMMV was recorded up to 58.1% in district Nowshera, followed by 51.1% in district Charsada, 40.5% in district Swabi and 37.3% in district Mardan. In Swat and Dir districts average incidence CGMMV was recorded upto 31.2% and 29.4%, respectively. Among the different crops highest incidence in plain areas of KPK was recorded in bottle gourd (59.3%) followed by 56.3% in Squash, 54.5% in Pumpkin, 45.5% in Melon, 41.7% in Cucumber and 29.9% in Sponge gourd. In Northern hilly areas highest incidence of CGMMV (52.9%) was observed in pumpkin, followed by 49.6% in bottle gourd, 47.3% in squash, 45.1% in Melon 42.3% in cucumber and 41.6% in sponge gourd. Little variability was observed in the coat protein amino acid sequence identities of CGMMV Pakistan isolate, when compared with other reported isolates.

Occurrence and molecular characterization of Cucumber green mottle mosaic virus in cucurbit crops of KPK, Pakistan

Field survey of the cucurbit crops revealed a high incidence of Cucumber green mottle mosaic virus (CGMMV) in Khyber Pakhtunkhwa Province (KPK), Pakistan. Among the seven districts surveyed, average percent incidence of CGMMV was recorded up to 58.1% in district Nowshera, followed by 51.1% in district Charsada, 40.5% in district Swabi and 37.3% in district Mardan. In Swat and Dir districts average incidence CGMMV was recorded upto 31.2% and 29.4%, respectively. Among the different crops highest incidence in plain areas of KPK was recorded in bottle gourd (59.3%) followed by 56.3% in Squash, 54.5% in Pumpkin, 45.5% in Melon, 41.7% in Cucumber and 29.9% in Sponge gourd. In Northern hilly areas highest incidence of CGMMV (52.9%) was observed in pumpkin, followed by 49.6% in bottle gourd, 47.3% in squash, 45.1% in Melon 42.3% in cucumber and 41.6% in sponge gourd. Little variability was observed in the coat protein amino acid sequence identities of CGMMV Pakistan isolate, when compared with other reported isolates.

Assessment of virus removal by managed aquifer recharge at three full-scale operations.

Managed aquifer recharge (MAR) systems such as riverbank filtration and soil-aquifer treatment all involve the use of natural subsurface systems to improve the quality of recharged water (i.e. surface water, stormwater, reclaimed water) before reuse. During MAR, water is either infiltrated via basins, subsurface injected or abstracted from wells adjacent to rivers. The goal of this study was to assess the removal of selected enteric viruses and a potential surrogate for virus removal at three full-scale MAR systems located in different regions of the United States (Arizona, Colorado, and California). Samples of source water (i.e., river water receiving treated wastewater and reclaimed water) before recharge and recovered groundwater at all three sites were tested for adenoviruses, enteroviruses, Aichi viruses and pepper mild mottle virus (PMMoV) by quantitative polymerase chain reaction (qPCR). Samples of groundwater positive for any virus were also tested for the presence of infectious virus by cell culture. PMMoV was the most commonly detected virus in the groundwater samples. Infectious enteric viruses (reovirus) were only detected in one groundwater sample with a subsurface residence time of 5 days. The results suggested that in groundwater with a residence time of greater than 14 days all of the viruses are removed below detection indicating a 1 to greater than 5 log removal depending upon the type of virus. Given its behavior, PMMoV may be suitable to serve as a conservative tracer of enteric virus removal in managed aquifer treatment systems.

TMV-Cg Coat Protein stabilizes DELLA proteins and in turn negatively modulates salicylic acid-mediated defense pathway during Arabidopsis thaliana viral infection.

BACKGROUND: Plant viral infections disturb defense regulatory networks during tissue invasion. Emerging evidence demonstrates that a significant proportion of these alterations are mediated by hormone imbalances. Although the DELLA proteins have been reported to be central players in hormone cross-talk, their role in the modulation of hormone signaling during virus infections remains unknown. RESULTS: This work revealed that TMV-Cg coat protein (CgCP) suppresses the salicylic acid (SA) signaling pathway without altering defense hormone SA or jasmonic acid (JA) levels in Arabidopsis thaliana. Furthermore, it was observed that the expression of CgCP reduces plant growth and delays the timing of floral transition. Quantitative RT-qPCR analysis of DELLA target genes showed that CgCP alters relative expression of several target genes, indicating that the DELLA proteins mediate transcriptional changes produced by CgCP expression. Analyses by fluorescence confocal microscopy showed that CgCP stabilizes DELLA proteins accumulation in the presence of gibberellic acid (GA) and that the DELLA proteins are also stabilized during TMV-Cg virus infections. Moreover, DELLA proteins negatively modulated defense transcript profiles during TMV-Cg infection. As a result, TMV-Cg accumulation was significantly reduced in the quadruple-DELLA mutant Arabidopsis plants compared to wild type plants. CONCLUSIONS: Taken together, these results demonstrate that CgCP negatively regulates the salicylic acid-mediated defense pathway by stabilizing the DELLA proteins during Arabidopsis thaliana viral infection, suggesting that CgCP alters the stability of DELLAs as a mechanism of negative modulation of antiviral defense responses.

A simplified approach to construct infectious cDNA clones of a tobamovirus in a binary vector.

Infectious cDNA clones of RNA viruses are important tools to study molecular processes such as replication and host-virus interactions. However, the cloning steps necessary for construction of cDNAs of viral RNA genomes in binary vectors are generally laborious. In this study, a simplified method of producing an agro-infectious Pepper mild mottle virus (PMMoV) clone is described in detail. Initially, the complete genome of PMMoV was amplified by a single-step RT-PCR, cloned, and subcloned into a small plasmid vector under the T7 RNA polymerase promoter to confirm the infectivity of the cDNA clone through transcript inoculation. The complete genome was then transferred to a binary vector using a single-step, overlap-extension PCR. The selected clones were agro-infiltrated to Nicotiana benthamiana plants and showed to be infectious, causing typical PMMoV symptoms. No differences in host responses were observed when the wild-type PMMoV isolate, the T7 RNA polymerase-derived transcripts and the agroinfiltration-derived viruses were inoculated to N. benthamiana, Capsicum chinense PI 159236 and Capsicum annuum plants.

Occurrence and molecular characterization of Cucumber green mottle mosaic virus in cucurbit crops of KPK, Pakistan.

Field survey of the cucurbit crops revealed a high incidence of Cucumber green mottle mosaic virus (CGMMV) in Khyber Pakhtunkhwa Province (KPK), Pakistan. Among the seven districts surveyed, average percent incidence of CGMMV was recorded up to 58.1% in district Nowshera, followed by 51.1% in district Charsada, 40.5% in district Swabi and 37.3% in district Mardan. In Swat and Dir districts average incidence CGMMV was recorded upto 31.2% and 29.4%, respectively. Among the different crops highest incidence in plain areas of KPK was recorded in bottle gourd (59.3%) followed by 56.3% in Squash, 54.5% in Pumpkin, 45.5% in Melon, 41.7% in Cucumber and 29.9% in Sponge gourd. In Northern hilly areas highest incidence of CGMMV (52.9%) was observed in pumpkin, followed by 49.6% in bottle gourd, 47.3% in squash, 45.1% in Melon 42.3% in cucumber and 41.6% in sponge gourd. Little variability was observed in the coat protein amino acid sequence identities of CGMMV Pakistan isolate, when compared with other reported isolates.

Evidence for plant viruses in the region of Argentina Islands, Antarctica.

This work focused on the assessment of plant virus occurrence among primitive and higher plants in the Antarctic region. Sampling occurred during two seasons (2004/5 and 2005/6) at the Ukrainian Antarctic Station 'Academician Vernadskiy' positioned on Argentina Islands. Collected plant samples of four moss genera (Polytrichum, Plagiatecium, Sanionia and Barbilophozia) and one higher monocot plant species, Deschampsia antarctica, were further subjected to enzyme-linked immunosorbent assay to test for the presence of common plant viruses. Surprisingly, samples of Barbilophozia and Polytrichum mosses were found to contain antigens of viruses from the genus Tobamovirus, Tobacco mosaic virus and Cucumber green mottle mosaic virus, which normally parasitize angiosperms. By contrast, samples of the monocot Deschampsia antarctica were positive for viruses typically infecting dicots: Cucumber green mottle mosaic virus, Cucumber mosaic virus and Tomato spotted wilt virus. Serological data for Deschampsia antarctica were supported in part by transmission electron microscopy observations and bioassay results. The results demonstrate comparatively high diversity of plant viruses detected in Antarctica; the results also raise questions of virus specificity and host susceptibility, as the detected viruses normally infect dicotyledonous plants. However, the means of plant virus emergence in the region remain elusive and are discussed.