Genus Comovirus Research Articles

Biological, serological and molecular comparison between isolates of Cowpea severe mosaic virus

ABSTRACT Cowpea, Vigna unguiculata, can be affected by several diseases, and those caused by viruses are considered of great importance. Cowpea severe mosaic virus (CPSMV), which belongs to the family Comoviridae, genus Comovirus, stands out for its severity and degree of incidence. Its genetic variability can give rise to different strains around the world, including in Brazil. The objective of the present research was to establish a biological, serological and molecular comparison between five CPSMV isolates obtained from naturally infected plants in different States of the Northeast of Brazil. Isolates were obtained from cowpea: CPSMV-AL (State of Alagoas), CPSMV- CE (Ceara); CPSMV-MC (Piaui), CPSMV-PE (Pernambuco) and an isolate obtained from Crotalaria paulinea, in the State of Maranhao - CPSMV-CROT. A host range study evidenced biological differences among the virus isolates, especially in cowpea genotypes. The isolates were showed to be serologically and molecularly related by polymerase chain reaction �� PCR, using degenerated primers which amplified two conserved regions in the coat protein and in the replicase genes. Cloning and sequence of CPSMV-PE made possible its comparison with other CPSMV isolates and other virus species from the genus Comovirus.

Studies on the tolerance of soybean (Glycine max,/i> (l.) Merrill) to Bean Pod Mottle Virus (BPMV) (genus Comovirus) in humid tropical zone of Nigeria

The reaction of twenty soybean varieties to inoculation with Bean Pod Mottle Virus (BPMV) (Genus comovirus) was studied for two consecutive years both in the field and in the greenhouse. Randomized Complete Block Design (RCBD) with three replications was used for the field studies while completely Randomized Design (CRD) with three replications was used for the greenhouse studies. The tolerance of soybean varieties to BPMV was investigated using Bean Leaf Beetle (Cerotoma trifurcata) and Gross Wounding Inoculation Technique (GWIT). The twenty soybean varieties studied differed significantly (P = 0.05) in the incidence and disease severity ratings of BPMV disease. TGX 1835-3E produced the highest (73.8%) incidence, while TGX 1864-25F gave the lowest (8.80%) incidence of BPMV disease in the field. TGX 1875-2E had the highest (3.9) disease severity rating of BPMV while TGX 1843-3E and TGX 1448-1E had the lowest (2.3 each) rating. BPMV was transmitted to soybean varieties by Gross Wounding Inoculation Technique (GWIT) (61.7%) and by bean leaf beetle (Cerotoma trifurcata) (51.5%). Keywords: Bean leaf beetle, Gross wounding inoculation technique, Transmission, Incidence, Bean pod mottle virusPlant Product Research Journal Vol. 12 2008: pp. 14-18

Virus-induced gene silencing in Medicago truncatula and Lathyrus odorata

Virus-induced gene silencing (VIGS) has become an important reverse genetics tool for functional genomics. VIGS vectors based on Pea early browning virus (PEBV, genus Tobravirus) and Bean pod mottle virus (genus Comovirus) are available for the legume species Pisum sativum and Glycine max, respectively. With the aim of extending the application of the PEBV VIGS vector to other legumes, we examined susceptibility of 99 accessions representing 24 legume species including 21 accessions of Medicago truncatula and 38 accessions Lotus japonicus. Infectivity of PEBV was tested by agro-inoculation with a vector carrying the complete β-glucuronidase (GUS) coding sequence. In situ histochemical staining analysis indicated that 4 of 21 M. truncatula and three of three Lathyrus odorata accessions were infected systemically by GUS tagged PEBV, while none of 38 L. japonicus accessions displayed GUS staining of either inoculated or uninoculated leaves. Agro-inoculation of plants representing PEBV-GUS susceptible M. truncatula and L. odorata accessions with PEBV carrying a fragment of Phytoene desaturase (PDS) resulted in development of a bleaching phenotype suggesting a down-regulation of PDS expression. In M. truncatula this was supported by quantification of PDS mRNA levels by real-time PCR.

Turnip ringspot virus recognised on Chinese cabbage in Russia

The nucleotide sequence of the 3′-terminal part of the RNA1 genome segment of the M12 isolate of comovirus Turnip ringspot virus (TuRSV) was established. This isolate originated in 1989 in Moscow (Russia) from Chinese cabbage with Radish mosaic virus-like symptoms. Comparison of the M12 RNA polymerase amino acid sequence with that of Radish mosaic virus (RaMV) revealed significant differences; these proteins are of different length and are only about 75% identical. On the other hand, the amino acid sequence of the M12 RNA polymerase was more than 94% identical with that of TuRSV recently described in Toledo (USA). We conclude that TuRSV occurs in Europe as well as in America and probably represents a new species of the genus Comovirus.

Molecular Characterization of Naturally Occurring RNA1 Recombinants of the Comovirus Bean pod mottle virus

ABSTRACT The Bean pod mottle virus, a member of the genus Comovirus, has a bipartite genome consisting of RNA1 and RNA2. We previously reported the occurrence in nature of two distinct subgroups of BPMV strains (subgroups I and II), as well as reassortants between the two subgroups. Here, we report on the isolation and molecular characterization of RNA1 recombinants from soybean plants infected with the partial diploid reassortant strain IL-Cb1, which induces very severe symptoms on soybean. cDNA cloning and sequencing of RNA1 from strain IL-Cb1 revealed the presence of chimeric and mosaic recombinant RNA1s. The full-length mosaic and chimeric recombinant RNA1s were infectious and induced mild symptoms on soybean. Although the recombinant RNA1 accumulated to high levels in the absence of wild-type RNA1, its accumulation level was low in mixed infections with wild-type RNA1. Recombinant RNA1 molecules with similar structures to the naturally occurring recombinant RNA1s were generated in soybean after four passages following inoculation with RNA1 transcripts derived from cDNAs of two distinct strains. This suggests that recombination events are frequent and that a recombination hot spot exists. Sequence analysis of the recombination region showed that it has AU-rich sequences characteristic of recombination hot spots.

No-Choice Preference of <I>Cerotoma trifurcata</I> (Coleoptera: Chrysomelidae) to Potential Host Plants of Bean Pod Mottle Virus (<I>Comoviridae</I>) in Iowa

To better understand the naturally occurring host range of Bean pod mottle virus (family Comoviridae, genus Comovirus, BPMV) and its principal vector Cerotoma trifurcata (Förster) (Coleoptera: Chrysomelidae), 18 field-collected perennial plant species were tested for the presence of BPMV. By using no-choice assays, we determined the preference of these plants by bean leaf beetle, by measuring their level of herbivory relative to soybean, Glycine max (L.). New food hosts for adult bean leaf beetles include Lespedeza capitata (Michaux), Lotus corniculatus L., Trifolium alexandrinum L., Trifolium ambiguum Bieberstein, and Trifolium incarnatum L. Desmodium illinoense Gray is discovered as a new naturally occurring host for BPMV.

Genome sequence of a Japanese isolate of Radish mosaic virus: the first complete nucleotide sequence of a crucifer-infecting comovirus

The complete nucleotide sequences of RNA1 and RNA2 of a Japanese isolate of Radish mosaic virus (RaMV-J), a crucifer-infecting comovirus, were determined. RNA1 is 6064 nucleotides long and encodes a 210-kDa polyprotein containing conserved motifs that are required for replication. RNA2 is 4020 nucleotides long and encodes a 123-kDa polyprotein containing the putative movement protein and two coat proteins. Comparisons of the encoded proteins confirmed that RaMV-J and a Czech RaMV isolate are isolates of the same species in the genus Comovirus. A phylogenetic analysis of RaMV-J and other comoviruses revealed that legume-infecting comoviruses constitute a single branch to which RaMV is distantly related.

First Report of Japanese Beetle (Popillia japonica) as a Vector of Southern bean mosaic virus and Bean pod mottle virus

The Japanese beetle, Popillia japonica (Coleoptera: Scarabaeidae), was introduced into the United States in New Jersey in 1916 and now commonly occurs in the eastern and mid-western United States. The Japanese beetle has a wide host range and feeds on more than 300 plant species within 79 families (2), but it has not been reported to be a vector of plant viruses. Southern bean mosaic virus (SBMV; genus Sobemovirus) and Bean pod mottle virus (BPMV; family Comoviridae, genus Comovirus) are transmitted by several species of leaf-feeding beetles in the families Coccinelidae and Chrysomelidae (1). Japanese beetles, collected in northwestern Arkansas with a JB Jumbo insect trap (Great Lakes IPM, Inc., Vestaburg, MI), were tested to determine if they are able to transmit SBMV and BPMV. The beetles were given a 24-h acquisition access (individually in plastic petri dishes) to detached trifoliolate leaves of Phaseolus vulgaris 'Black Valentine' systemically infected with either BPMV or SBMV. Beetles that had fed on the infected bean leaves (as evidenced by feeding damage to the leaves) were caged individually in clear plastic cups on healthy 'Black Valentine' bean seedlings for a 24-h transmission access period. The test plants were grown in the greenhouse for 2 weeks after which they were evaluated for virus infection. In the first trial, BPMV was not transmitted (0 of 11 bait plants with feeding damage), whereas SBMV was efficiently transmitted (6 of 6 bait plants with feeding damage) as determined by agar-gel double-diffusion serology of test plants using polyclonal antibodies to SBMV and BPMV. In a second trial, with a different set of beetles, the transmission rate for BPMV was 3 of 46 (6.5%) and 33 of 43 (77%) for SBMV, and the test plants were evaluated for virus infection using Protein A ELISA. The higher transmission efficiency of SBMV by Japanese beetles when compared with BPMV is characteristic of these two viruses when they are transmitted by other leaffeeding beetles (1). These results are in contrast to an earlier report that Japanese beetles were not able to transmit BPMV from infected soybeans to healthy soybeans in Illinois (3). To our knowledge, this is the first report that the Japanese beetle, an introduced insect with a wide host range in the United States, is a vector of plant viruses.

Controlling bean pod mottle virus (BPMV) (Genus <i> Comovirus </i> of soybean with spatial arrangement of maize-soybean in southeastern Nigeria

Field cultural practices of controlling Bean Pod Mottle Virus (BPMV) (genus comovirus) disease, involving thirteen spatial arrangements of maize/soybean (M:S) were studied for 2 years in Nsukka agro-ecological zone of Nigeria. Factorial arrangement of treatments in a randomized complete block design with three replications was used. Thirteen spatial arrangements of maize/soybean (M:S) constituted a factor while the health conditions of soybean plants (healthy and infected) constituted another factor. The thirteen spatial arrangements of maize/soybean (M:S) studied differed significantly in the incidence of BPMV disease. Spatial arrangement of 2:4 recorded the highest (82.5%) incidence, though statistically similar with spatial arrangements of 0:4(sole soyabean) (71.3%), 1:4 (76.3%) and 3:4 (70.0%). spatial arrangement of 3:1 recorded the lowest (7.5%) incidence though statistically similar with spatial arrangement of 1:1 (13.8%) and 1:2 (18.9%). Spatial arrangement of 1:2 recorded the highest (69.4) number of pods and grain yields (1.42t/ha), while the spatial arrangement, 3:1 recorded the lowest (40.80) number of pods and grain yield. Health conditions of the soybean plant affected significantly the yield. Healthy soybean plant produced the highest (1.49t/ha) grain yield while infected soybean plant produced the lowest grain yield.of 0..82 t / ha. Keywords : Spatial arrangement, Bean leaf beetle, Bean pod Mottl virus, Maize, Soybean. Agro-Science Vol. 3 (2) 2006: pp. 27-34

Genes diferentes podem conferir resistência ao Cowpea severe mosaic virus em caupi

O caupi (Vigna unguiculata) é uma importante leguminosa cultivada principlamente por pequenos agricultores da região Nordeste. Doenças ocasionadas por vírus podem constituir o principal fator limitante da produção do caupi, destacando-se, nesse aspecto, o mosaico severo, causado pelo Cowpea severe mosaic virus (CpSMV), família Comoviridae, gênero Comovirus. A resistência tem sido considerada como a melhor alternativa no controle dessa virose e diversas fontes promissoras têm sido relatadas, como as cultivares Macaibo e CNC 0434, e a linhagem L254.008. As investigações sobre a base genética da resistência ao CpSMV nesses materiais têm conduzido a resultados semelhantes, sendo a resistência herdada como uma característica monogênica recessiva. No entanto, até então, nenhum trabalho havia investigado o alelismo dos genes de resistência dessas fontes. No presente trabalho foram realizados estudos visando esclarecer essa questão nas três fontes de resistência; 'Macaibo', 'CNC0434' e L254.008. Plantas dos referidos genótipos foram cruzadas de maneira direta e recíproca originando seis populações F1 e F2. Inoculações controladas dessas populações com o isolado CpSMV-Re1 permitiram concluir que o gene de resistência de 'Macaibo' é o mesmo de 'CNC-0434', distinto daquele encontrado na linhagem L254.008.

Occurrence of Radish mosaic virus on Cauliflower and Turnip Crops in Iran.

During the spring and summer of 2003, symptoms of mosaic, mottle, and crinkle were observed in cauliflower (Brassica oleracea) and turnip (Brassica rapa) fields in the Qazvin and Esfahan provinces of Iran, respectively. Leaf extracts of these plants, made infective by mechanical inoculation, caused necrotic local lesions on Chenopodium amaranticolor, chlorotic ring spot on Nicotiana tabacum cv. Samsun, and chlorotic local lesions followed by systemic mosaic on Brassica rapa (1). Using double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and specific polyclonal antibodies (As-0120 and PV-0355) that were kindly prepared by S. Winter (DSMZ, Braunschweig, Germany), the samples were tested for the presence of Radish mosaic virus (RaMV) (family Comoviridae, genus Comovirus). ELISA results showed that the original leaf samples and inoculated indicator plants reacted positively to RaMV antibodies. RaMV has been reported in the United States, Japan, and Europe on turnip and other crucifers (1,2). To our knowledge, this is the first report of RaMV occurring in Iran.

First record of Chickpea chlorotic dwarf virus (CpCDV) affecting faba bean (Vicia faba) crops in Egypt

A field visit was conducted in March 2002 to identify viruses infecting the faba bean ( Vicia faba ) crop in four governorates (Fayoum, Beni Suef, El-Nobareia and Bihera) in Egypt. A total of 71 faba bean samples with symptoms of viral infection (leaf rolling, yellowing and mosaic) were collected. These were tested at the Virology Laboratory of ICARDA, Syria, for seven viruses using the tissue-blot immunoassay procedure (Makkouk & Comeau, 1994). Specific rabbit polyclonal antisera were used to test for Chickpea chlorotic dwarf virus (CpCDV, genus Mastrevirus , family Geminiviridae ; provided by H. J. Vetten, BBA, Braunschweig, Germany); for Broad bean stain virus (BBSV, genus Comovirus , family Comoviridae ); for Bean yellow mosaic virus (BYMV, genus Potyvirus , family Potyviridae ) and for Pea seed borne mosaic virus (PSbMV, genus Potyvirus , family Potyviridae ). In addition, three specific monoclonal antibodies were used to detect Faba bean necrotic yellows virus (FBNYV, genus Nanovirus , family Nanoviridae ) (Franz et al ., 1996); Bean leaf roll virus (BLRV, family Luteoviridae ) (4B10; Katul, 1992) and Beet western yellows virus (BWYV, genus Polerovirus , family Luteoviridae ) (ATCC PVAS-647; American Type Culture Collection, Manassas, VA, USA). Serological tests showed that BYMV, an aphid-transmitted and seedborne virus that was identified in 89% of samples tested, was the most common virus. In most of the fields surveyed, BYMV symptoms were noted to occur at high levels (80–100% infection). PSbMV was detected in nine samples (one from Fayoum and eight from Beni Suef); FBNYV was detected in 11 samples (all from Beni Suef). CpCDV, a leafhopper-transmitted virus, was, by contrast, detected in only two samples collected from the El-Nobareia governorate showing leaf rolling, yellowing and stunting. BWYV, BLRV and BBSV were not detected in any of the samples tested. In Egypt, FBNYV, BYMV and PSbMV have previously been reported in faba bean (Makkouk et al ., 1994), but this is the first record of CpCDV affecting faba bean in Egypt. CpCDV is the only member of the Geminivirus that is reported to naturally infect faba bean.

Diversity Among Isolates ofBean pod mottle virus

ABSTRACT Isolates of Bean pod mottle virus (BPMV), a member of the genus Comovirus, collected from soybean fields in Kentucky, Virginia, Arkansas, and Iowa were classified into two distinct subgroups, I and II, based on nucleic acid hybridization analysis using cloned cDNA probes to RNA-1 from BPMV strains K-G7 and K-Ha1. Slot blot hybridization analysis using cloned cDNA probes to RNA-2 from the same two strains (K-G7 and K-Ha1), however, revealed that some of the isolates, initially classified as belonging to subgroup I after analysis with RNA-1 probes, are in fact natural reassortants between the two strain subgroups. This was corroborated by nucleotide sequence analysis of full-length cDNA clones of both RNA-1 and RNA-2 from a putative reassortant strain (K-Ho1). These results indicate that BPMV strain diversity is more complex than initially anticipated, and that the use of cloned probes to both genomic RNAs during nucleic acid hybridization analysis is required to unravel the extent of such diversity. In a field plot experiment, BPMV isolates that belong to distinct strain subgroups induced symptoms that varied in severity and in the level of yield losses. In this regard, the reassortant strain K-Ho1 caused the most serious damage compared with four other BPMV isolates tested. Furthermore, the soybean alleles Rsv(1) and Rsv(4), known to confer resistance against Soybean mosaic virus, a member of the genus Potyvirus, did not provide any protection against BPMV. Additionally, we developed a reverse transcription-polymerase chain reaction procedure based on the sequence of a highly conserved region in the capsid polyprotein coding sequence that provides efficient and highly sensitive detection of all BPMV isolates tested, regardless of their strain classification.

Survey of Faba Bean ("Vicia faba" L.) Virus Diseases in Ethiopia

Surveys conducted in 1996 and 1997 to assess the status of virus diseases affecting faba bean in the major growing areas of Ethiopia indicated that leaf yellowing, rolling, necrosis and stunting were the most common disease symptoms. The highest visually-observed disease incidence in a field was 85%, recorded in the Wello region (north-eastern Ethiopia). When 3049 symptomatic samples collected from 211 fields from all over Ethiopia were tested by the tissue blot immunoassay (TBIA) for 14 viruses, 1592 samples (52.2%) were found to be infected with at least one virus. Faba bean necrotic yellows virus (FBNYV, genus Nanovirus) was the most frequent (63.2%), followed by luteoviruses (28.5%) [such as Beet western yellows virus (BWYV, genus Polerovirus, family Luteoviridae) and Bean leaf roll virus (BLRV, family Luteoviridae)] and Chickpea chlorotic dwarf virus (CCDV, genus Mastrevirus, family Geminiviridae) (3.1%). Mosaic/mottling symptoms were observed in some fields but incidence was always very low (<1%). The mosaic/mottling causing viruses identified were Broad bean stain virus (BBSV) and Broad bean true mosaic virus (BBTMV) (genus Comovirus, family Comoviridae), Pea seed-borne mosaic virus (PSbMV) and Bean yellow mosaic virus (BYMV) (genus Potyvirus, family Potyviridae). Testing of 3035 random samples collected in 1997 from 37 fields in the Shewa and Arsi regions revealed 1.6% luteovirus and 0.6% FBNYV infection, indicating that the incidence of these viruses on faba bean is very low in central Ethiopia. The survey suggested that virus diseases are currently of economic importance on faba bean in north-eastern Ethiopia and potentially important in the other areas, with FBNYV and luteoviruses being the most important.

Comovirus isolation and RNA extraction.

Comoviruses are small, icosahedral viruses with a diameter of approx 28 nm (Fig. 1). Presently the genus Comovirus is comprised of 15 different viruses, of which the type species, cowpea mosaic virus (CPMV), is the most thoroughly studied (,). All viruses are transmitted by beetles and have a rather narrow host range. Most comoviruses have legumes as their natural hosts and usually cause mosaic or mottling symptoms. Comoviruses are mechanically transmissible, and can replicate to high levels in infected cells. Purified preparations of comoviruses consist of two, sometimes three, distinguishable particles, which can be separated by centrifugation on sucrose density gradients. These particles are designated as bottom (B), middle (M), and top (T) component, corresponding to their position in the centrifuge tube. The B- and M-component are nucleoprotein particles, each containing a segment of the single-stranded, bipartite RNA genome (denoted RNA-1 and RNA-2, respectively); T-component consists of empty protein shells. Both B- and M-components, or their RNAs, are necessary for infectivity (). Open image in new window Fig. 1. Genetic organization of the CPMV genome. The icosahedral virus particles consist of two components, denoted B and M, that contain RNA-1 and RNA-2, respectively. The ORFs in the RNA molecules are indicated with open bars and VPg with a black square. The RNAs are translated into polyproteins that are proteolytically processed at six specific sites, indicated below the ORFs, into several stable intermediate and nine final cleavage products. These latter products are indicated in the ORFs. Functions of the different domains in the polyproteins are shown above the ORFs with the following abbreviations: MP, movement protein; CO-PRO, cofactor required for proteinase; HEL?, putative helicase; PRO, proteinase; POL, RNA-dependent RNA polymerase.