Groundnut Ringspot Virus Research Articles

First report of a tospovirus in a commercial crop of Cape gooseberry in Brazil

Viruses from the genus Tospovirus (family Bunyaviridae) are widespread in the Americas, where the following species have been reported: Tomato chlorotic spot virus (TCSV), Tomato spotted wilt virus (TSWV), Groundnut ringspot virus (GRSV), Chrysanthemum stem necrosis virus (CSNV), Zucchini lethal chlorosis virus (ZLCV), Impatiens necrotic spot virus (INSV), Iris yellow spot virus (IYSV) (Jones, 2005), Alstroemeria necrotic streak virus (ANSV), Melon severe mosaic virus (MeSMV) and Bean necrotic mosaic virus (BeNMV) (Ciuffo et al., 2009; Hassani-Mehraban et al., 2010; Oliveira et al., 2011). This work describes the identification of a virus isolated from a commercial crop of Cape gooseberry (Physalis peruviana) in October 2009 in Santa Maria, State of Rio Grande do Sul, Brazil. The disease was identified in a 5 ha cultivated area, where 100% of the plants were showing symptoms of stunting, mosaic, necrosis and foliar distortion (Fig. 1). Spherical particles measuring 80-100 nm in diameter were observed by electron microscopy, giving the initial evidence that a tospovirus might be involved in the disease. Sap from the infected leaves of five different Cape gooseberry plants were inoculated on healthy indicator plants: Petunia hybrida and Chenopodium amaranticolor reacted with local lesions; Datura stramonium, Solanum gilo, S. lycopersicum, S. nigrum, Physalis angulata, P. floridana and P. peruviana (Fig. 1) displayed systemic symptoms. Host reactions were typical for those caused by tospoviruses and symptoms on Physalis species reproduced those observed in the original samples. Testing by plate trapped-ELISA, a positive reaction was only obtained from all five samples using anti-TCSV antiserum (Embrapa, CNPH, Brazil). Negative ELISA results were obtained using antiserum against four other tospoviruses: Tomato spotted wilt virus, Groundnut ringspot virus, Impatiens necrotic spot virus and Chrysanthemum stem necrosis virus. RT-PCR was performed using primers designed to conserved regions of the tospoviral S RNA (Eiras et al., 2001). This generated 440 bp DNA fragments, whose sequence revealed a high degree of nucleotide identity with TCSV isolates from Argentina (98-99%) and Brazil (93-95%). Alignment of the partial coat protein nucleotide sequences showed that the Physalis TCSV isolate (GenBank Accession No. JQ034525) clustered with other TCSV isolates, sharing a clade with Argentinean isolates (Fig. 2). Cape gooseberry is a fruit crop of great nutritional and economic value, which has gradually gained acceptance in international markets, due to its flavour and medicinal properties. In Brazil, it was introduced as a commercial crop into small farms in southern Brazil (Rufato et al., 2008). To our knowledge, this is the first report of natural occurrence of TCSV in commercial crops of Cape gooseberry. To date the disease is restricted to Rio Grande do Sul State. Further epidemiological studies are necessary for understanding the spread of TCSV into this relatively new introduced crop in Brazil.

Sequence determination and analysis of the NSs genes of two tospoviruses

The tospoviruses groundnut ringspot virus (GRSV) and zucchini lethal chlorosis virus (ZLCV) cause severe losses in many crops, especially in solanaceous and cucurbit species. In this study, the non-structural NSs gene and the 5'UTRs of these two biologically distinct tospoviruses were cloned and sequenced. The NSs sequence of GRSV and ZLCV were both 1,404 nucleotides long. Pairwise comparison showed that the NSs amino acid sequence of GRSV shared 69.6% identity with that of ZLCV and 75.9% identity with that of TSWV, while the NSs sequence of ZLCV and TSWV shared 67.9% identity. Phylogenetic analysis based on NSs sequences confirmed that these viruses cluster in the American clade.

Groundnut Ringspot Virus in Florida

Groundnut ringspot virus was recently identified in tomatoes in South Florida — the first report in the United States. It can infect tomato plants at all stages of growth and lead to unmarketable fruits or plant death. This 4-page fact sheet shares what is known about the symptoms, host range, disease transmission, and management. Written by Eugene McAvoy, Scott Adkins, Craig Webster, Charles Mellinger, Loren Horsman, Galen Frantz, Stuart Reitz, and Shouan Zhang, and published by the UF Department of Plant Pathology, July 2011.

Erratum to: Molecular characterization of the RNA-dependent RNA polymerase from groundnut ringspot virus (genus Tospovirus, family Bunyaviridae)

Erratum to: Molecular characterization of the RNA-dependent RNA polymerase from groundnut ringspot virus (genus Tospovirus, family Bunyaviridae)

Molecular characterization of the RNA-dependent RNA polymerase from groundnut ringspot virus (genus Tospovirus, family Bunyaviridae)

Groundnut ringspot virus is a negative-sense single-stranded RNA virus that belongs to the genus Tospovirus and is the prevalent member of this genus in Brazil. This work presents the nucleotide sequence of the L RNA, with a single open reading frame of 2873 amino acids in the complementary strand corresponding to the RNA-dependent RNA polymerase (L protein), as well as the characterization of conserved domains of the L protein by in silico analysis. Phylogenetic analysis of different L protein domains confirmed that GRSV is a member of the American clade, and comparison with a N-protein indicates that phylogeny based on L protein sequences may be more reliable than that based on the N protein.

A natural M RNA reassortant arising from two species of plant- and insect-infecting bunyaviruses and comparison of its sequence and biological properties to parental species

Reassortment allows multicomponent viruses to exchange genome segments, a process well-documented in the vertebrate- and arthropod-infecting members of the family Bunyaviridae but not between distinct species of the plant- and insect-infecting members of the genus Tospovirus. Genome sequence comparisons of a virus causing severe tospovirus-like symptoms in Florida tomato with Groundnut ringspot virus (GRSV) and Tomato chlorotic spot virus (TCSV) demonstrated that reassortment has occurred, with the large (L) and small (S) RNAs coming from GRSV and the medium (M) RNA coming from TCSV (i.e. L GM TS G). Neither parental genotype is known to occur in the U.S. suggesting that L GM TS G was introduced as a reassortant. L GM TS G was transmitted by western flower thrips ( Frankliniella occidentalis [Pergande]), and was not able to overcome the Sw5 resistance gene of tomato. Our demonstration of reassortment between GRSV and TCSV suggests caution in defining species within the family Bunyaviridae based on their ability to reassort.

First Report of Impatiens necrotic spot virus in Gentiana macrophylla in China.

Large leaf gentian, Gentiana macrophylla Pall., known as Qin Jiao in Chinese, is a medicinal herb. Its root is most commonly used in Chinese traditional medicine to relieve rheumatic conditions and to remove damp-heat. During a survey in July 2009, large leaf gentian plants exhibiting foliar chlorotic and necrotic spots as well as severe stunting were collected in Lijiang County, Yunnan Province of China. Incidence of symptomatic plants ranged from 10 to 30% in the field. Symptomatic leaves from five different G. macrophylla plants were collected and tested for Impatiens necrotic spot virus (INSV), Tomato spotted wilt virus, Watermelon silver mottle virus, Groundnut bud necrosis virus, Tomato chlorotic spot virus, and Groundnut ringspot virus by double-antibody sandwich-ELISA kits (Agdia Inc., Elkhart, IN). All tested samples were positive only for INSV. To further confirm the presence of INSV, reverse transcription (RT)-PCR was conducted. Total RNA was extracted from the symptomatic large leaf gentian plants leaves with a RNeasy Plant Kit (Qiagen Inc., Valencia, CA) and used as a template in RT-PCR using forward (5'-CTT TGC TTT TTA GAA CTG TGC A-3') and reverse (5'-AGA GCA ATT GTG TCA CGA ATA T-3') primers specific to the partial INSV nucleoprotein (N) gene (GenBank No. DQ425096). Amplicons of the expected size (approximately 760 bp) were obtained from all ELISA-positive samples. Three clones were sequenced and the partial nucleocapsid protein genes consensus sequences of these isolates were determined (GenBank No. HQ317133). Nucleotide sequences of large leaf gentian isolates shared 98 to 99% nucleotide identity with INSV sequences of isolates from China, Italy, Japan, United States, and the Netherlands (GenBank Nos. FN400772, GQ336989, DQ425096, AB109100, D00914, AB109100, and X66972). INSV is one of the most serious viral pathogens of ornamental plants in North America, Europe, and Asia (1-3). To our knowledge, this is the first report of natural occurrence of INSV in G. macrophylla in China.

Search in Solanum (section Lycopersicon) germplasm for sources of broad-spectrum resistance to four Tospovirus species

The genus Tospovirus was considered as monotypic with Tomato spotted wilt virus (TSWV) being the only assigned species. However, extensive studies with worldwide isolates revealed that this genus comprises a number of species with distinct virulence profiles. The Neotropical South America is one center of Tospovirus diversity with many endemic species. Groundnut ringspot virus (GRSV), TSWV, Tomato chlorotic spot virus (TCSV), and Chrysanthemum stem necrosis virus (CSNV) are the predominant tomato-infecting species in Brazil. Sources of resistance were found in Solanum (section Lycopersicon) mainly against TSWV isolates from distinct continents, but there is an overall lack of information about resistance to other viral species. One-hundred and five Solanum (section Lycopersicon: Solanaceae) accessions were initially evaluated for their reaction against a GRSV isolate by analysis of symptom expression and systemic virus accumulation using DAS-ELISA. A subgroup comprising the most resistant accessions was re-evaluated in a second assay with TSWV, TCSV, and GRSV isolates and in a third assay with a CSNV isolate. Seven S. peruvianum accessions displayed a broad-spectrum resistance to all viral species with all plants being free of symptoms and systemic infection. Sources of resistance were also found in tomato cultivars with the Sw-5 gene and also in accessions of S. pimpinellifolium, S. chilense, S. arcanum, S. habrochaites, S. corneliomuelleri, and S. lycopersicum. The introgression/incorporation of these genetic factors into cultivated tomato varieties might allow the development of genetic materials with broad-spectrum resistance, as well as with improved levels of phenotypic expression.

Expansion of Groundnut ringspot virus Host and Geographic Ranges in Solanaceous Vegetables in Peninsular Florida

To the best of our knowledge, this is the first report of GRSV infecting tomatillo and eggplant, and it is the first report of GRSV infecting pepper in the United States. This first identification of GRSV-infected crop plants in commercial fields in Palm Beach and Manatee Counties demonstrates the continuing geographic spread of the virus into additional vegetable production areas of Florida. This information indicates that a wide range of solanaceous plants is likely to be infected by this emerging viral pathogen in Florida and beyond. Accepted for publication 27 June 2011. Published 25 July 2011.

Diverging Affinity of Tospovirus RNA Silencing Suppressor Proteins, NSs, for Various RNA Duplex Molecules

The tospovirus NSs protein was previously shown to suppress the antiviral RNA silencing mechanism in plants. Here the biochemical analysis of NSs proteins from different tospoviruses, using purified NSs or NSs containing cell extracts, is described. The results showed that all tospoviral NSs proteins analyzed exhibited affinity to small double-stranded RNA molecules, i.e., small interfering RNAs (siRNAs) and micro-RNA (miRNA)/miRNA* duplexes. Interestingly, the NSs proteins from tomato spotted wilt virus (TSWV), impatiens necrotic spot virus (INSV), and groundnut ringspot virus (GRSV) also showed affinity to long double-stranded RNA (dsRNA), whereas tomato yellow ring virus (TYRV) NSs did not. The TSWV NSs protein was shown to be capable of inhibiting Dicer-mediated cleavage of long dsRNA in vitro. In addition, it suppressed the accumulation of green fluorescent protein (GFP)-specific siRNAs during coinfiltration with an inverted-repeat-GFP RNA construct in Nicotiana benthamiana. In vivo interference of TSWV NSs in the miRNA pathway was shown by suppression of an enhanced GFP (eGFP) miRNA sensor construct. The ability to stabilize miRNA/miRNA* by different tospovirus NSs proteins in vivo was demonstrated by increased accumulation and detection of both miRNA171c and miRNA171c* in tospovirus-infected N. benthamiana. All together, these data suggest that tospoviruses interfere in the RNA silencing pathway by sequestering siRNA and miRNA/miRNA* molecules before they are uploaded into their respective RNA-induced silencing complexes. The observed affinity to long dsRNA for only a subset of the tospoviruses studied is discussed in light of evolutional divergence and their ancestral relation to the animal-infecting members of the Bunyaviridae.

First Report of Impatiens necrotic spot virus Infecting Phalaenopsis and Dendrobium Orchids in Yunnan Province, China.

In November 2007, leaves of 79 Phalaenopsis and two Dendrobium orchid plants in a nursery in Yunnan Province showed large chlorotic/necrotic ringspot symptoms. Eight symptomatic leaves from Phalaenopsis and two from Dendrobium were sampled and tested for Impatiens necrotic spot virus (INSV), Tomato spotted wilt virus (TSWV), Watermelon silver mottle virus (WSMoV), Groundnut bud necrosis virus (GBNV), Tomato chlorotic spot virus (TCSV), and Groundnut ringspot virus (GRSV) with double-antibody sandwich (DAS)-ELISA kits (Agdia Inc., Elkhart, IN). All samples were positive for INSV and negative for TSWV, WSMoV, GBNV, TCSV, and GRSV. Total RNA extracts were prepared from all ELISA-positive samples with the RNeasy extraction kit (Huashun Inc., Shanghai, China). Reverse transcription (RT)-PCR was carried out with specific primers to the INSV N gene (ZI2F, 5'-GTTTAGCCTTACCAAT-3' and ZI2R, 5'-TACCAACAACCGTGAA-3'), designed from a sequence of GenBank Accession No. AB109100. All ELISA-positive samples yielded an amplification product of the expected 539 bp as observed by gel electrophoresis in 1% agarose. Three clones from each isolate were sequenced and two N gene consensus sequences of the isolates from Phalaenopsis and Dendrobium were determined (GenBank Nos. GU289904 and GU289905, respectively). Nucleotide sequences of these two Chinese orchid isolates were 98 to 99% identical with sequences of isolates from the Netherlands, United States, Italy, and Japan (GenBank Nos. X66972, D00914, DQ425096 and AB109100, respectively). To our knowledge, this is the first report of INSV infecting Phalaenopsis and Dendrobium in Yunnan Province, although INSV has been reported in Oncidium in Yunnan Province previously (2), and the first time that INSV has been detected in Dendrobium. An investigation of the orchid nurseries looking for the thrips vector (1) of INSV was performed and a few thrips were found, suggesting that thrips may not be responsible for the observed prevalence of INSV in these nurseries. The orchids were imported from Taiwan and reproduced by tissue culture and it is possible that INSV found to be infecting orchids in these Yunnan nurseries may be from the infected source plant and was not eradicated completely through tissue culture. To reduce spread of INSV, virus-free tissue culture should be a priority for orchid production.

A distinct tospovirus causing necrotic streak on Alstroemeria sp. in Colombia

A tospovirus causing necrotic streaks on leaves was isolated from Alstroemeria sp. in Colombia. Infected samples reacted positively with tomato spotted wilt virus (TSWV) antiserum during preliminary serological tests. Further analysis revealed a close serological relationship to tomato chlorotic spot virus (TCSV) and groundnut ringspot virus (GRSV). A major part of the S-RNA segment, encompassing the nucleocapsid (N) protein gene, the 5′ untranslated region and a part of the intergenic region 3′ of the N gene, was cloned and sequenced. The deduced N protein sequence showed highest amino acid identity (82%) to that of TCSV, indicating that the virus represents a new tospovirus species, for which the name Alstroemeria necrotic streak virus (ANSV) is coined. Phylogenetic analysis based on the N protein sequence revealed that this Alstroemeria-infecting tospovirus clustered with tospoviruses from the American continent. Frankliniella occidentalis was identified as potential vector species for ANSV.

First Report of Groundnut ringspot virus Infecting Tomato in South Florida

To the best of our knowledge this is the first report of GRSV in the United States in any host, although TSWV has been present in Florida for many years. Although the detection of GRSV in Florida tomatoes is cause for concern, the close relationship of GRSV and TSWV may allow successful adaptation of the integrated disease management strategies currently in use for TSWV in tomatoes for management of GRSV. Accepted for publication 17 May 2010. Published 7 July 2010.

Occurrence, Prevalence, and Distribution of Viruses Infecting Peanut in Argentina.

This is the first survey to determine the occurrence, prevalence, and distribution of peanut (Arachis hypogaea) viral diseases in Argentina. It was conducted in the province of Córdoba, which has 92% of the country's peanut production. It included the main peanut viruses Peanut mottle virus (PeMoV), Peanut stripe virus (PStV), Cucumber mosaic virus (CMV), Peanut stunt virus (PSV), Tomato spotted wilt virus (TSWV), and Groundnut ringspot virus (GRSV). Leaf samples from 1,028 individual peanut plants with virus-like symptoms and 986 samples from asymptomatic plants were collected in six counties of Córdoba over 3 years and serologically tested for the presence of viruses. PeMoV was the most frequently detected virus, found in 58.8, 34.2, and 23.4% of samples from the 2003-04, 2004-05, and 2005-06 growing seasons, respectively, and it was found in all sampled counties. Also, it was the only virus detected in asymptomatic plants. Less than 4% of symptomatic plants were infected with CMV or GRSV; 0.5, 3.6, and 2% of samples were positive for CMV; and 0.5, 3.1, and 1.6% were positive for GRSV in the 2003-04, 2004-05 and 2005-06 seasons, respectively. Some mixed infections were found: CMV-PeMoV and GRSV-PeMoV. During this survey, PSV, PStV, and TSWV were not detected in any peanut samples.

Identification and characterization of a tospovirus causing chlorotic ringspots on Phalaenopsis orchids

A putative virus-induced disease showing chlorotic ringspots on leaves of Phalaenopsis orchids has been observed in Taiwan for several years. A virus culture, 91-orchid-1, isolated from a Phalaenopsis orchid bearing chlorotic ringspot symptoms was established in Chenopodium quinoa and Nicotiana benthamiana, and characterized serologically and biologically. The virus reacted slightly with the antiserum of Watermelon silver mottle virus (WSMoV) but not with those of Tomato spotted wilt virus (TSWV), Impatiens necrotic spot virus (INSV) and Groundnut ringspot virus (GRSV). Isometric particles measuring about 70–100 nm were observed. Inoculation with isolated virus was conducted to confirm that 91-orchid-1 is the causal agent of chlorotic ringspot disease of Phalaenopsis orchids. To determine the taxonomic relationships of the virus, the conserved region of L RNA and the complete nucleocapsid gene (N gene) were cloned and sequenced. The sequence of conserved region of L RNA shares 83.8, 82.5, 64.4 and 64.9% nucleotide identities and 96.5, 97.7, 67.3 and 67.6% amino acid identities with those of Peanut bud necrosis virus (PBNV), WSMoV, TSWV and INSV, respectively, indicating that 91-orchid-1 is a tospovirus related to WSMoV. The complete nucleotide sequence of the N gene determined from a cDNA clone was found to be 828 nucleotides long encoding 275 amino acids. Sequence analyses of the N gene showed that 91-orchid-1 is an isolate of Capsicum chlorosis virus (CaCV) which has been reported to infect tomato and capsicum plants in Australia and Thailand. 91-orchid-1 is therefore designated as CaCV-Ph. To our knowledge, this is the first formal report of a tospovirus infecting Phalaenopsis orchids.

Groundnut ringspot virus: an Emerging Tospovirus Inducing Disease in Peanut Crops

AbstractPeanut (Arachis hypogaea L.) plants showing Tospovirus‐like symptoms were observed in Córdoba province (central Argentina). Peanut plants were collected and tested to identify the causal agent. Tospovirus‐like particles were observed by electron microscopy and Groundnut ringspot virus (GRSV) was identified by double antibody sandwich‐enzyme‐linked immunosorbent assay (DAS‐ELISA) and reverse transcription‐polymerase chain reaction (RT‐PCR). Partial nucleotide and deduced amino acid sequences of the nucleocapsid (N) gene indicated a high degree of identity with other GRSV sequences. This is the first report of the GRSV occurrence on peanuts in Argentina.

Characterisation of cineraria strain ofTomato yellow ring virusfrom Iran

A tospovirus isolated from naturally infected cineraria plants in commercial greenhouses in Shiraz, Iran, induced rings and chlorotic and necrotic spots on leaves, growth reduction and death of the plants. The viruswas transmitted by three populations of Thrips tabaci. Antisera were produced against purified virions and viral nucleocapsids and used to study the virus host range and relationships. On the basis of enzyme-linked immunosorbent assay, tomato, anemone, Arum sp., dandelion and pepper were natural hosts of the virus. SDS-PAGE revealed three major structural proteins corresponding to the Tospovirus N, G1 and G2 proteins. Three RNA segments were resolved in a 1% agarose gel with molecular masses of 1.02×106 Da, 1.87×106 Da and 2.86×106 Da, corresponding to the virus S, M and L RNAs, respectively. No serological relationships were detected between the cineraria virus and Tomato spotted wilt virus, Tomato chlorotic spot virus and Groundnut ring spot virus using the virus nucleocapsid IgG in dot immunobinding assays. Further characterisation by nucleotide sequencing of the virus N gene revealed that it was a strain of Tomato yellow ring virus, although the cineraria isolate appears to have a different experimental host range compared to tomato isolates of the virus.

Characterization of Tomato fruit yellow ring virus: a new Tospovirus species infecting tomato in Iran

During surveys for Tomato spotted wilt virus (TSWV) in the major tomato production areas of Iran, tomato fruits showing a bright yellow ring pattern were observed, from which a tospovirus was isolated by mechanical transmission to herbaceous hosts. The virus originated from the Varamin area where >30% of the tomato crop was infected with TSWV. Although typical tospovirus virions were found by electron microscopy, a panel of antibodies used for detection and identification of tospoviruses by ELISA failed to react with this isolate. An antiserum against virus nucleoprotein preparations (DSMZ-AS0526) reacted specifically with plants infected with the new isolate, but not with other tospoviruses. Analysis of the S RNA genome comprising the N-protein gene (275 aa; GenBank accession number AJ493270) and a segment of the L gene (GenBank accession number AJ493271), to determine the taxonomic position of the virus, confirmed that this is a distinct tospovirus species, sharing 72–75% nucleoprotein amino acid identity with isolates of Iris yellow spot virus (IYSV), its closest relative. A 42–45% N-protein similarity with N-gene sequences of tospoviruses from Asia (Watermelon silver mottle virus, Melon yellow spot virus and Watermelon bud necrosis virus), and only 28–30% amino acid sequences in common with tospoviruses from Europe–Africa (TSWV, Tomato chlorotic spot virus and Groundnut ringspot virus), further confirmed its taxonomic position. The absence of any detectable serological relationships, and the limited sequence similarity with IYSV and other tospoviruses, justify the classification of this new virus as a distinct species of the genus Tospovirus for which the name Tomato fruit yellow ring virus (TFYRV) is proposed. This virus has an extensive host range (Ghotbi et al., 2005), but is found most often in tomato and in mixed virus infections with TSWV.

Evaluation of Arabidopsis thaliana response to infection by Tomato spotted wilt virusand Groundnut ringspot virus

In Brazil the occurrence of different tospovirus species such as Tomato spotted wilt virus (TSWV) and Groundnut ringspot virus (GRSV) has been reported (De Avila et al., J. Gen. Virol. 74:153. 1993; De Avila et al., Arch. Virol. 128:211. 1993). Arabidopsis thaliana is currently the most studied plant and has had its genome completely sequenced since the year 2000. The ecotype Columbia of A. thaliana has been shown to be a host to TSWV (German et al., Plant Mol. Biol. Rep. 13:110. 1995). Here we expand on this previous report by describing in detail disease symptoms on A. thaliana and evaluating the response of 20 different ecotypes to TSWV. We also describe, for the first time, the symptoms of GRSV infection on Arabidopsis plants. Arabidopsis thaliana ecotypes CS903, CS920, CS1020, CS1072, CS1084, CS1194, CS1308, CS1354, CS1438, CS1466, CS1492,CS1540, CS1566, CS1594, CS1640, CS1643, CS2223, CS3112, CS6100, CS6699 were obtained from ABRC (Ohio, U.S.A.). Three to four weeks-old plants grown under continuous fluorescent illumination (100 imol.m-2.s-1), 24 °C and 50% relative humidity were used in all experiments. Rosette leaves of all 20 ecotypes were mechanically inoculated with TSWV, isolate BR-01 (De Avila et al., J. Gen. Virol. 71:2801. 1990). Symptoms of infection appeared two weeks after inoculation and ranged from mild to strong, sometimes leading to plant death, depending on the ecotype. Common symptoms were the development of chlorotic and necrotic spots (Figure 1). Sometimes chlorotic rings and deformation of leaves with curling, as well as purpling of leaves, inhibition of plant growth and reduced fertility were observed. All ecotypes showed positive DAS-ELISA results in at least one of the timepoints tested 12, 20 or 35 days post inoculation (d.p.i.) (Clark & Adams, J. Gen. Virol. 34:475. 1977). For experiments with GRSV isolate A5, six ecotypes (CS1194, CS1298, CS1308, CS1540, CS1640 and CS6922) were selected and their rosette leaves were mechanically inoculated. Symptoms such as leaf necrosis and chlorotic and necrotic spots were noticeable two weeks after inoculation. The bolt of many plants became contorted and stunting and inhibition of silique (pod) growth were also observed (Figure 1). Wrinkling of cauline leaves indicates that GRSV infection is systemic on A. thaliana. Symptoms correlated with GRSV detection by DASELISA at 14 d.p.i. on all tested ecotypes. All ecotypes tested were susceptible to the tospoviruses studied. Arabidopsis thaliana is a great model system for performing genetic experiments. Future studies such as mutant screens for increased susceptibility or resistance to TSWV and GRSV will provide the opportunity for uncovering plant genes involved in the plant-tospovirus interaction.

Relationships between Tospovirus Incidence and Thrips Populations on Tomato in Mendoza, Argentina

AbstractThe objectives of this work were to estimate the capability of local populations of thrips as vectors of groundnut ringspot virus (GRSV) and tomato spotted wilt virus (TSWV), and to determine the species composition of vectors in tomato crops. Transmission assays were performed. Incidence of tospoviruses was estimated in commercial crops. Random samples of flowers were taken from tomato for identification of thrips. Of the five species of thrips tested, Frankliniella gemina (first record), F. occidentalis and F. schultzei transmitted GRSV and TSWV. F. schultzei was a significantly more efficient vector of GRSV than F. occidentalis under controlled assay conditions. The thrips were identified on flowers from six surveyed tomato crops. F. occidentalis was the most frequently identified species (43.0%), followed by F. schultzei (35.6%) and Thrips tabaci (10.1%). The incidence of tospoviruses was low (1.1–2.8%) in crops planted during August–September and greater (9.5–61.1%) in crops planted in December. GRSV was prevalent (85%) over TSWV (11%).