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Sugar beet cultivation is dependent on an effective control of beet necrotic yellow vein virus (BNYVV, family Benyviridae), which causes tremendous economic losses in sugar production. As the virus is transmitted by a soilborne protist, the use of resistant cultivars is currently the only way to control the disease. The Rz2 gene product belongs to a family of proteins conferring resistance towards diverse pathogens in plants. These proteins contain coiled-coil and leucine-rich repeat domains. After artificial inoculation of homozygous Rz2 resistant sugar beet lines, BNYVV and beet soilborne mosaic virus (BSBMV, family Benyviridae) were not detected. Analysis of the expression of Rz2 in naturally infected plants indicated constitutive expression in the root system. In a transient assay, coexpression of Rz2 and the individual BNYVV-encoded proteins revealed that only the combination of Rz2 and triple gene block protein 1 (TGB1) resulted in a hypersensitive reaction (HR)-like response. Furthermore, HR was also triggered by the TGB1 homologues from BSBMV as well as from the more distantly related beet soilborne virus (family Virgaviridae). This is the first report of an R gene providing resistance across different plant virus families.

Background Plant viral diseases are difficult to control and have caused serious damage to the agricultural industry. Recently, botanical biopesticides characterized by environment friendly, safe to non-target organism and not as susceptible to produce drug resistance, have exhibited great potential to be developed as antiviral agents. To screen the natural products with antiviral effect, three alkaloids possessed anti-tobacco mosaic virus (TMV) activity were isolated from Chelidonium majus and the modes of action were investigated. Result The anti-TMV effect of crude extracts at 10 mg mL-1 was 51.73%. Bioassay-guided fractionation and isolation of the compounds with anti-TMV activity were performed on the methanol extract of C. majus yielding three bioactive alkaloids namely: chelerythrine (1), chelidonine (2), and sanguinarine (3). The results of bioassay showed that chelerythrine exhibited great inactivation, proliferation inhibition and protection effects against TMV at 0.5 mg mL-1 with the efficiency of 72.67%, 77.52% and 59.34%, respectively. Chelidonine at 0.1 mg mL-1 can provide 54.90% and 64.45% inhibitions on TMV through inducing resistance in two kinds of tobacco. Sanguinarine showed a weaker protection for resisting TMV in comparison to chelerythrine and chelidonine. Conclusion Chelerythrine and chelidonine displayed significant inhibitions on TMV with different modes of action. These results provided important evidence that the extracts in C. majus might be a potential source of new drugs in controlling virus disease agriculturally.

Following a request from the EU Commission, the Panel on Plant Health addressed the pest categorisation of the viruses and viroids of Vitis L. determined as being either non-EU or of undetermined standing in a previous EFSA opinion. These infectious agents belong to different genera and are heterogeneous in their biology. With the exclusion of grapevine virus 101-14.N.23.9.1/South Africa/2009 for which very limited information exists, the pest categorisation was completed for 30 viruses or viroids having acknowledged identities and available detection methods. All these viruses are efficiently transmitted by vegetative propagation techniques, with plants for planting representing the major pathway for long-distance dispersal and thus considered as the major pathway for potential entry. Depending on the virus, additional pathway(s) can also be seeds, pollen and/or vector(s). Most of the viruses categorised here are known to infect only one or few plant genera, but some of them have a wide host range, thus extending the possible entry pathways. Grapevine yellow speckle viroid 2, blueberry leaf mottle virus, grapevine Ajinashika virus, grapevine Anatolian ringspot virus, grapevine berry inner necrosis virus, grapevine deformation virus, grapevine fabavirus, grapevine red blotch virus, grapevine stunt virus, grapevine Tunisian ringspot virus, grapevine vein-clearing virus, temperate fruit decay-associated virus, peach rosette mosaic virus, tobacco ringspot virus, tomato ringspot virus meet all the criteria evaluated by EFSA to qualify as potential Union quarantine pests (QPs). With the exception of impact for the EU territory, on which the Panel was unable to conclude, blackberry virus S, grapevine geminivirus A, grapevine leafroll-associated virus 7, grapevine leafroll-associated virus 13, grapevine satellite virus, grapevine virus E, grapevine virus I, grapevine virus J, grapevine virus S, summer grape enamovirus, summer grape latent virus satisfy all the other criteria to be considered as potential Union QPs. Australian grapevine viroid, grapevine cryptic virus 1, grapevine endophyte endornavirus and wild vitis virus 1 do not meet all the criteria evaluated by EFSA to be regarded as potential Union QPs because they are not known to cause an impact on Vitis. For several viruses, especially those recently discovered, the categorisation is associated with high uncertainties mainly because of the absence of data on their biology, distribution and impact. Since this opinion addresses specifically non-EU viruses, in general these viruses do not meet the criteria assessed by EFSA to qualify as a potential Union regulated non-quarantine pests.

A new virus tentatively named watermelon green mottle mosaic virus (WGMMV) was isolated from watermelon leaves showing mottle, mosaic and leaf crinkling symptoms in Taiwan. Electron microscopy identified tobamovirus‐like, rod‐shaped particles measuring about 18 nm × 300 nm in the crude saps. The enzyme‐linked immunosorbent assay (ELISA) tests of symptomatic watermelon leaves using an antiserum against Cucumber green mottle mosaic virus (CGMMV) resulted in negative reactions. Genomic fragments of WGMMV were amplified by reverse transcription‐polymerase chain reaction (RT‐PCR) using degenerate primers of cucurbit‐infecting tobamovirus. Sequence analysis revealed that WGMMV genome contains 6,482 nucleotides (Gen Bank accession no. MH837097). WGMMV coat protein (CP) gene shares 55.9–82.2% nucleotide identities and 42.6–87.7% amino acid sequence identities and its complete genome shares 62.0–80.9% nucleotide sequence identities with other cucurbit‐infecting tobamoviruses. Thus, WGMMV is a new tobamovirus. The virion origin of assembly sequence (OAS) containing a conserved GAGGUUG was found in the CP‐coding region of CGMMV, WGMMV and Cucumber mottle virus (CuMoV). A comparison of genome organisation has revealed that both WGMMV and CuMoV, belonging to the sub‐subgroup III, have a 29‐nt overlap between the movement protein and CP coding genes. Full‐length nucleotide sequence of WGMMV shares 80.9% identity with that of CuMoV. Watermelon seedlings inoculated with WGMMV showed similar symptoms with the diseased plants observed in the field. WGMMV proliferated in the inoculated seedlings as evidenced by the ELISA and western blotting analyses. Mechanical inoculation assays revealed that WGMMV caused mosaic symptoms in a wide array of cucurbitaceous plants. A primer pair specifically complementary to the WGMMV CP‐coding gene was designed and used to successfully detect WGMMV using RT‐PCR. The primers and WGMMV‐specific antiserum will be useful for rapid detection of WGMMV.

Begomoviruses (whitefly-transmitted, single-stranded DNA plant viruses) are among the most damaging pathogens causing epidemics in economically important crops worldwide. Besides cultivated plants, many weed and wild hosts act as virus reservoirs where recombination may occur, resulting in new species. The aim of this study was to further characterise the diversity of begomoviruses infecting two major weed genera, Sida and Leonurus. Total DNA was extracted from samples collected in the states of Rio Grande do Sul, Parana and Mato Grosso do Sul during the years 2009–2011. Viral genomes were enriched by rolling circle amplification (RCA), linearised into unit length genomes using various restriction enzymes, cloned and sequenced. A total of 78 clones were obtained: 37 clones from Sida spp. plants and 41 clones from Leonurus sibiricus plants. Sequence analysis indicated the presence of six bipartite begomovirus species and two alphasatellites. In Sida spp. plants we found Sida micrantha mosaic virus (SiMMV), Euphorbia yellow mosaic virus (EuYMV), and three isolates that represent new species, for which the following names are proposed: Sida chlorotic mottle virus (SiCMoV), Sida bright yellow mosaic virus (SiBYMV) and Sida golden yellow spot virus (SiGYSV), an Old World-like begomovirus. L. sibiricus plants had a lower diversity of begomoviruses compared to Sida spp., with only Tomato yellow spot virus (ToYSV) and EuYMV (for the first time detected infecting plants of the genus Leonurus) detected. Two satellite DNA molecules were found: Euphorbia yellow mosaic alphasatellite, for the first time detected infecting plants of the genus Sida, and a new alphasatellite associated with ToYSV in L. sibiricus. These results constitute further evidence of the high species diversity of begomoviruses in non-cultivated hosts, particularly Sida spp.

Rye production in European growing areas is constrained by the soilborne cereal mosaic virus (SBCMV) and the wheat spindle streak mosaic virus (WSSMV). To date, no European rye cultivars are known to exhibit resistance against these viruses. In this study, we pursued a quantitative trait locus (QTL) mapping strategy to identify genomic regions for resistance to SBCMV and WSSMV in rye. Three populations, each comprising 100 lines segregating for resistance to SBCMV and/or WSSMV, were evaluated for disease response at two years in three locations in Germany where soils are naturally infested with SBCMV and WSSMV. In the combined analysis across environments, one QTL for SBCMV resistance on chromosome 5R explained 31.9% of the phenotypic variation in one of the populations. For WSSMV resistance, one QTL explaining up to 64.0% of the phenotypic variation was detected on chromosome 7R in each of the three populations. On the Triticeae homoeologous group 5, we found evidence for synteny of the major QTL for SBCMV resistance between the wheat and rye genomes.

The shrinkage of fossil fuel resources motivates many countries to search alternative energy sources. Jatropha curcas is a small drought-resistant shrub from whose seeds a high grade fuel biodiesel can be produced. It is cultivated in many tropical countries including India. However, the plant is affected by the mosaic virus (Begomovirus) through infected white-flies (Bemisia tabaci) which causes mosaic disease. Disease control is an important factor to obtain healthy crop but in agricultural practice, farming awareness is equally important. Here, we propose a mathematical model for media campaigns for raising awareness among people to protect this plant in small plots and control disease. In order to archive high crop yield, we consider the awareness campaign to be arranged in impulsive way to make people aware from infected white-flies to protect Jatropha plants from mosaic virus. The study reveals that the spread of mosaic disease can be contained or even eradicated by the awareness campaigns. To attain an effective eradication, awareness campaign should be implemented at sufficiently short time intervals. Copyright © 2016 John Wiley & Sons, Ltd.

The Panel on Plant Health performed a pest categorisation of Longidorus diadecturus (Nematoda: Longidoridae) for the EU. The nematode is a well‐defined taxon and was described from Ontario, Canada and later reported from some states in the USA. The nematode is not present in the EU. It is regulated by Council Directive 2000/29/EC, listed in Annex I A I as L. diadecturus Eveleigh and Allen. It is a migratory ectoparasitic nematode species puncturing cells of plant roots thereby able to transmit the nepovirus Peach rosette mosaic virus (PRMV). The pest is found in soil associated with plant species belonging to different families. L. diadecturus is able to cause direct damage to plants, but its main damage is caused by vectoring PRMV. Soil is a potential pathway for this nematode for entry into the EU. The nematode is able to survive adverse conditions, but the virus may not persist inside the nematode for extended periods. Climatic conditions in the EU are similar to those found in the countries where the pest is currently present. Hosts of the nematode (and the associated virus) are, e.g. peaches and grapes; those crops are also widely cultivated in the EU. The nematode only moves short distances (around 1 m) but may be spread with soil moving activities. Measures are available to inhibit entry via soil as such. Entry of the nematode with soil attached to plants for planting that are not regulated is possible. L. diadecturus does satisfy all the criteria that are within the remit of EFSA to assess to be regarded as a potential Union quarantine pest.

Cowpea (Vigna unguiculata) is one of the most important legumes cultivated in many parts of the world. The diseases caused by Cowpea severe mosaic virus (CPSMV) and Cowpea aphid-borne mosaic virus (CABMV) are considered among the most important constraints on yield and quality, especially in Latin America and Africa. Here, the concept of using an RNA interference construct to silence the CPSMV proteinase cofactor gene and the CABMV coat protein gene is explored, in order to generate resistant transgenic cowpea plants. Ten cowpea transgenic lines were produced, presenting a normal phenotype and transferring the transgene to the next generation. Plants were tested for resistance to both CABMV and CPSMV by mechanical co-inoculation. Seven lines presented milder symptoms when compared to the control and three lines presented enhanced resistance to both viruses. Northern analyses were carried out to detect the transgene-derived small interfering RNA (siRNA) in leaves and revealed no correlation between siRNA levels and virus resistance. Additionally, in the symptomless resistant lines the resistance was homozygosis-dependent. Only homozygous plants remained uninfected while hemizygous plants presented milder symptoms.

Three new chromones are isolated and shown to exhibit anti-tobacco mosaic virus activities.

The outbreak of a severe mosaic disease with a significant incidence was noticed on Jatropha curcas plants growing in Lucknow, Northern India. The causal virus was successfully transmitted by whiteflies (Bemisia tabaci) and grafting from naturally infected to healthy J.curcas plants. The association of Begomovirus with the mosaic disease of J.curcas was detected by PCR using primers specific to DNA-A of Begomoviruses. Further, full-length DNA-A genome of 2.7 kb was amplified by RCA followed by digestion with Bam HI restriction enzyme. Cloning and sequencing of obtained amplicons resulted in 2740 nucleotides of complete DNA-A consisting of six ORFs and IR region (GenBank Accession HM230683). The sequence analysis revealed highest 85% similarities with Jatropha curcas mosaic virus, 7784% with Indian cassava mosaic virus and 7376% with Sri Lankan cassava mosaic virus isolates. Phylogenetic analysis of the Begomovirus isolate also showed a clear-cut distinct relationship with earlier reported Begomoviruses from Jatropha curcas and other Begomoviruses. On the basis of the guidelines of the International Committee on Taxonomy of Viruses (ICTV-2008), our virus isolate was identified as a possible strain of Indian cassava mosaic virus, and its name Jatropha mosaic India virus (JMIV) is proposed.

Two new 4-hydroxyisoflavanes, cordifoliflavanes A and B (1 and 2), were isolated from the roots of Codonopsis cordifolioidea. Their structures were elucidated by spectroscopic methods, including extensive 1D- and 2D-NMR techniques. Compounds 1 and 2 were tested for their anti-HIV-1 activities and anti-tobacco mosaic virus activities. The results showed that compounds 1 and 2 have modest anti-HIV-1 activities and anti-tobacco mosaic virus activities, respectively.

Large cardamom (Amomum subulatum), an important spice crop grown in eastern sub-Himalayan mountains of India, is affected by a viral disease commonly known as ‘chirke’, which is characterised by light and dark green streaks on the leaf lamina. Although chirke has been known to affect large cardamom for over 50 years, its distribution in large cardamom growing regions and aetiology have remained unaddressed. In this study for the first time, distribution of chirke in the major large cardamom growing regions in India has been determined. North Sikkim and eastern region of Darjeeling hills were endemic region with average disease incidence of 19.2–35%, whereas, Mirik region of Darjeeling hills were free from the disease. Suckers, the commonly used planting material, were the major source for spread of the disease. The virus was sap transmissible to the popular large cardamom cultivars Golsey, Ramsey, Swaney and Varlangey and vectored by Rhopalosiphum maidis and Myzus persicae in a non-persistent manner. Flexuous virus particles measuring 625–650 × 12.5 nm were observed consistently associated with the diseased samples. Polyclonal antiserum to the purified virus showed serological affinity with a macluravirus, cardamom mosaic virus (CdMV) associated with a similar disease known as katte disease of small cardamom (Elettaria cardamomum) occurring in southern India. The 3 � terminal genome sequence (1776 nucleotides) of the virus was determined, which revealed a close sequence identity and phylogenetic relationships with the members of the genus Macluravirus. The deduced amino acid sequence of putative coat protein (CP) gene showed maximum similarity of 65.7% with the CdMV. Phylogenetic analysis based on CP and 3 � UTR showed that the virus was closer to Alpinia mosaic virus ,C dMV andChinese yam necrotic mosaic virus subclade. The results suggest that the virus associated with the chirke disease of large cardamom is a new species under the genus Macluravirus in the family Potyviridae for which the name large cardamom chirke virus (LCCV) is proposed.

NE01481' (Reg. No. CV-1061, PI 659689) hard red winter wheat (Triticum aestivum L.) was developed cooperatively by the Nebraska Agricultural Experiment Station and the USDA-ARS and released in April 2010. NE01481 will be marketed as Husker Genetics brand McGill. In addition to superior agronomic performance, Nebraska wheat growers would like to have increased resistance to Wheat soilborne mosaic virus. NE01481 was selected from the cross NE92458/'Ike' that was made in 1995. The pedigree of NE92458 is OK83201/'Redland' and the pedigree of OK83201, an experimental line developed by Oklahoma State University is 'Vona'//'Chisholm'/'Plainsman V'. NE01481 was selected with the bulk- breeding method as an F 3:4 line in 1999, and in 2001 it was assigned experimental line number NE01481. NE01481 was released because of its superior grain yield in rainfed wheat production systems in southeastern, south central, and southwestern Nebraska and that it is the fi rst modern release from our program with resistance to Wheat soilborne mosaic virus.

Cowpea aphid-borne mosaic virus (CABMV) causes major diseases in cowpea and passion flower plants in Brazil and also in other countries. CABMV has also been isolated from leguminous species including, Cassia hoffmannseggii, Canavalia rosea, Crotalaria juncea and Arachis hypogaea in Brazil. The virus seems to be adapted to two distinct families, the Passifloraceae and Fabaceae. Aiming to identify CABMV and elucidate a possible host adaptation of this virus species, isolates from cowpea, passion flower and C. hoffmannseggii collected in the states of Pernambuco and Rio Grande do Norte were analysed by sequencing the complete coat protein genes. A phylogenetic tree was constructed based on the obtained sequences and those available in public databases. Major Brazilian isolates from passion flower, independently of the geographical distances among them, were grouped in three different clusters. The possible host adaptation was also observed in fabaceous-infecting CABMV Brazilian isolates. These host adaptations possibly occurred independently within Brazil, so all these clusters belong to a bigger Brazilian cluster. Nevertheless, African passion flower or cowpea-infecting isolates formed totally different clusters. These results showed that host adaptation could be one factor for CABMV evolution, although geographical isolation is a stronger factor.

Hepatitis B virus (HBV) is classified into seven major genotypes (A-H). Brazil, a country of continental proportions, has three prevailing lineages of HBV genotypes A, D, and F. Distinct HBV genotypes have been associated with differential risk of disease progression. Pre-S gene deletions and single nucleotide polymorphisms have also been linked to progression to liver diseases. In this study, the molecular epidemiology of HBV was examined in Southern Brazil. The occurrence of multiple HBV infections, HBV recombination, and genetic markers of disease progression were also evaluated. Seventy-eight persons infected with HBV had their viruses characterized molecularly by nested PCR, DNA sequencing, and phylogenetic inference. Multiple infections and recombinant viruses were evaluated by clonal and bootscanning analyses. The vast majority (96%) of the strains belonged to different D subgenotypes. Three of the four strains with unresolved genotypic classification showed evidence of dual infections with distinct D subgenotypes by clonal analysis. There was also evidence of intragenotype mosaic viruses. While four viruses had pre-S deletions as major variants, another two displayed minor variants with such characteristics. One strain carried the F141L mutation, associated recently with increased risk of hepatocellular carcinoma. These results emphasize the need for monitoring HBV genotype distribution around South America, as well as for the presence of genetic markers of disease progression in subjects diagnosed with HBV recently.

SUMMARY Citrus tristeza virus (CTV), a phloem-restricted closterovirus infecting citrus, encodes three different silencing suppressors (p25, p20 and p23), one of which (p23) is a pathogenicity determinant that induces aberrations resembling CTV symptoms when expressed ectopically in transgenic citrus hosts. In this article, the effect of p23 ectopic expression on virus infection was examined in sweet orange (SwO), a highly susceptible host, and sour orange (SO), which severely restricts CTV cell-to-cell movement.Transgenic plants of both species ectopically expressing p23, or transformed with an empty vector, were graft inoculated with the mild CTV isolate T385 or with CTV-BC1/GFP, a clonal strain derived from the severe isolate T36 carrying the gene for the green fluorescent protein (GFP). CTV distribution in infected tissues was assessed by direct tissue blot immunoassay and fluorescence emission, and virus accumulation was estimated by quantitative real-time reverse transcriptasepolymerase chain reaction. CTV accumulation in p23-expressing and control SwO plants was similar, whereas the viral load in transgenic SO expressing p23 was 10‐10 5 times higher than in the cognate control plants. Although few infection foci composed of a single cell were observed in the phloem of CTVinfected control SO, the number of foci in p23-expressing plants was higher and usually comprised two to six cells,indicating viral cell-to-cell movement. CTV was detected in mesophyll protoplasts and cells from infected SO and SwO expressing p23, but not in similar protoplasts and cells from infected control plants. Our results show that the ectopic expression of p23 enables CTV to escape from the phloem and, in addition, facilitates systemic infection of the resistant SO host. This is the first report of a viral-encoded protein that enhances virus accumulation and distribution in woody hosts.

A small open reading frame, termed 'pipo', is embedded in the P3 cistron of potyviruses. Currently, knowledge on pipo and its role(s) in the life cycle of potyviruses is limited. The P3 and helper-component proteinase (HC-Pro) cistrons of Soybean mosaic virus (SMV) harbour determinants affecting virulence on functionally immune Rsv1-genotype soybeans. Interestingly, a key virulence determinant of SMV on Rsv1-genotype soybeans (i.e. soybeans containing the Rsv1 resistance gene) that resides at polyprotein codon 947 overlaps both P3 and a pipo-encoded codon. This raises the question of whether PIPO or P3 is the virulence factor. To answer this question, the corresponding pipo of an avirulent and two virulent strains of SMV were studied by comparative genomics, followed by syntheses and analyses of site-directed mutants. Our data demonstrate that the virulence of SMV on Rsv1-genotype soybeans is affected by P3 and not the overlapping pipo-encoded protein.

Begomoviruses were found to be the major viruses infecting tomato plants in the Philippines based on the surveys conducted from 2005 to 2006. Pepper-infecting begomoviruses were also detected. Isolates of four distinct begomovirus species, Ageratum yellow vein virus (AYVV), Tomato leaf curl Cebu virus (ToLCCeV), Tomato leaf curl Mindanao virus (ToLCMiV) and Tomato leaf curl Philippines virus (ToLCPV), were characterised at the DNA sequence level by comparing 20 DNA-As from tomato samples comprising 13 from Luzon, 2 from Cebu and 5 from Mindanao Islands, along with 3 DNA-As from pepper samples, 1 each from Luzon, Cebu and Mindanao Islands. Two of these species (ToLCCeV and ToLCMiV) were distinct novel begomoviruses, while AYVV was detected for the first time in the Philippines. By geographic distribution, two tomato begomoviruses (ToLCPV and ToLCCeV) were detected in Luzon and Cebu Islands. The ToLCMiV was also detected in Luzon Island. The three tomato begomoviruses, AYVV, ToLCCeV and ToLCMiV, were detected in Mindanao Island. A ToLCPV isolate infecting pepper was also detected in Luzon Island, while ToLCCeV was detected in pepper samples from Cebu and Mindanao Islands. The diversity of viruses and their distinct geographic distribution need to be taken into consideration in the development and deployment of resistance against begomoviruses in the Philippines. Strategies for the use of post-transcriptional gene silencing for the control of tomato-infecting begomoviruses in the Philippines are discussed.

A total of 983 cowpea accessions obtained from the University of California, Riverside (UCR) Cowpea Repository were analysed for seedborne viruses. A majority of the accessions originated from 11 countries representing different agroclimatic zones in sub-Saharan Africa, and included landraces, local cultivars and breeding lines. Following the initial grow-out tests, 69 cowpea accessions, mostly with symptoms of virus infection, were selected for further evaluation using a combination of host range, reverse transcription-polymerase chain reaction (RT-PCR) and sequence analyses. The analyses revealed that samples from 46 (67%) accessions harboured one or more known seedborne viruses of cowpea. These included seed samples of accessions originating from Botswana (13 accessions), Ghana (6), Nigeria (6), Mali (1), Kenya (5), Cameroon (7), Niger (4), Cote d'lvoire (1), Benin (1), India (1) and China (1). Viruses were identified by RT-PCR analysis of total RNAs extracted from suspected virus-infected samples using virus species-specific primers, as well as the cloning and sequencing of RT-PCR products amplified using virus genus- and family-specific degenerate oligonucleotide primers. The viruses identified included Cowpea aphid-borne mosaic virus (CABMV), Cucumber mosaic virus (CMV) and Southern bean mosaic virus (SBMV). Phylogenetic analysis of the deduced coat protein (CP) amino acid sequences of selected CMV isolates recovered from five agroclimatically distinct locations confirmed their affiliations as new members of CMV subgroup IB. This is the first time that seedborne viruses of cowpea accessions in a major collection (UCR) have been identified using RT-PCR and sequencing approaches.

Twenty-four isolates of Chilli veinal mottle virus (ChiVMV) from China, India, Indonesia, Taiwan and Thailand were analysed to determine their genetic relatedness. Pathogenicity of virus isolates was confirmed by induction of systemic mosaic and/or necrotic ringspot symptoms on Capsicum annuum after mechanical inoculation. The 3′ terminal sequences of the viral genomic RNA were determined. The coat protein (CP) coding regions ranged from 858 to 864 nucleotides and the 3′ untranslated regions (3′UTR) from 275 to 289 nucleotides in length. All isolates had the inverted repeat sequence GUGGNNNCCAC in the 3′UTR. The DAG motif, conserved in aphid-transmitted potyviruses, was observed in all isolates. All 24 isolates were considered as belonging to ChiVMV because of their high CP amino acid and nucleotide identity (more than 94·8 and 89·5%, respectively) with the reported ChiVMV isolates including the pepper vein banding virus (PVBV), the chilli vein-banding mottle virus (CVbMV) and the CVbMV Chiengmai isolate (CVbMV-CM1). Based on phylogenetic analysis, ChiVMV isolates including all 24 isolates tested, PVBV, CVbMV and CVbMV-CM1 can be classified into three groups. In addition, a conserved region of 204 amino acids with more than 90·2% identity was identified in the C terminal of the CP gene of ChiVMV and Pepper veinal mottle virus (PVMV), and may explain the serological cross reaction between these two viruses. The conserved region may also provide useful information for developing transgenic resistance to both ChiVMV and PVMV.

In a survey to detect viruses affecting Centrosema species in two agroecological zones in Nigeria (the derived and northern guinea savanna zones: DSZ and NGSZ), enzyme-linked immunosorbent assay of leaf samples of four species (C. brasilianum, C. pascuorum, C. pubescens and C. macrocarpum) revealed infections of two Potyviruses – Bean common mosaic virus and Cowpea aphid-borne mosaic virus – and three Comoviruses – Cowpea mosaic virus, Cowpea severe mosaic virus and Bean pod mottle virus. Other viruses detected included: a Carmovirus, Cowpea mottle virus; a Cucumovirus, Cucumber mosaic virus (CMV); a Sobemovirus, Southern bean mosaic virus; and a Tobamovirus known as Tobacco mosaic virus (TMV). While no viruses were detected in leaf samples of C. brasilianum and C. pubescens collected from NGSZ, leaf samples of the same species collected from DSZ were highly infected, with the former being infected with seven viruses and the latter with all nine viruses tested for. Seed transmission studies of these viruses in Centrosema species showed CMV to be the most frequently detected, followed by TMV, and four different viruses were found in seeds of C. brasilianum in DSZ. The paper discusses the implications of these results for cropping of Centrosema legumes. Copyright © 2008 John Wiley & Sons, Ltd

SUMMARY The yellow mosaic diseases of a number of legumes across Southern Asia are caused by four species of whitefly-transmitted geminiviruses (genus Begomovirus, family Geminiviridae): Mungbean yellow mosaic virus, Mungbean yellow mosaic India virus, Dolichos yellow mosaic virus and Horsegram yellow mosaic virus. They cause losses to a number of important pulse crops, a major source of dietary protein in the region. The viruses have host ranges limited to plants of the family Fabaceae and efforts to limit losses are hampered by limited availability of conventional resistance sources and/or the lack of durability of the resistance that has been identified. There is ample evidence for genetic interaction between these begomoviruses within the legumes, in the form of both classical recombination and component exchange, but little evidence for interaction with viruses that infect other plants. This is indicative of genetic isolation, the viruses in legumes evolving independently of the begomoviruses in plant species of other families. This has implications for the development of engineered resistance in legumes, which holds the promise of durability but has yet to be transferred to the field. Taxonomy: The viruses causing yellow mosaic diseases of legumes across southern Asia, four of which have been identified so far, are bipartite begomoviruses (genus Begomovirus, family Geminiviridae): Mungbean yellow mosaic virus, Mungbean yellow mosaic India virus, Horsegram yellow mosaic virus and Dolichos yellow mosaic virus. Physical properties: The legume yellow mosaic viruses (LYMVs), like all members of the Geminiviridae, have geminate (twinned) particles, 18–20 nm in diameter, 30 nm long, apparently consisting of two incomplete T = 1 icosahedra joined together in a structure with 22 pentameric capsomers and 110 identical protein subunits. Disease symptoms: Symptoms caused by LYMVs are largely dependent on host species and susceptibility. Initially symptoms appear as small yellow specks along the veins and then spread over the leaf. In severe infections the entire leaf may become chlorotic. In blackgram the chlorotic areas sometimes turn necrotic. Infections of French bean usually do not produce a mosaic but instead induce a downward leaf curling. Disease control: Control is based mainly on preventing the establishment of the whitefly vector, Bemisia tabaci, in the crop by application of insecticides. Changes in agricultural practices, such as moving the cropping period out of periods of high vector incidence (the wet period in late summer) to times of low vector incidence (dry season in early summer) have met with some, albeit short-term, benefits. The use of natural, host plant resistance is efficacious, although the available sources of resistance in most legume crops are limited. In mungbean the resistance is attributed to two recessive genes which are used effectively to control the disease. Useful websites: http://www.danforthcentre.org/iltab/geminiviridae/, http://www.iwglvv.org/

Three distinct viruses, named chloris striate mosaic virus (CSMV), paspalum striate mosaic virus (PaSMV) and digitaria didactyla striate mosaic virus (DDSMV), have been identified among the five Gramineae-infecting geminiviruses from Australia using polyclonal antisera. An isolate from Microlaena was confirmed as a strain of CSMV, and an isolate from Bromus catharticus was identified as PaSMV-BC. Enzyme-linked immunosorbent assay (ELISA) detected relationships between all but one of the viruses tested, the exception being miscanthus streak virus (MiSV) from Japan. The Australian viruses proved to be distantly related to similar viruses from Africa, digitaria streak virus (DSV) from Vanuatu, and wheat dwarf virus (WDV) from Europe. Three distinct groups of viruses from Africa, Australia and Europe were distinguished by phylogenetic analysis.

Development of a method to identify field tolerance to bean pod mottle and soybean mosaic viruses (BPMV and SMV) in soybean [Glycine max (L.) Merr.] allowed evaluation of 33 soybean accessions for field response to BPMV and SMV. Based on measurement of parameters that included relative level of virus antigen in seed and mottling of soybean seed coats, three accessions showed tolerance to SMV and BPMV (PI 561353, M90-18411, PI 507353), eight were tol­ erant to SMV (MN 1301, M92-160047, M91-113037, PI 423826A, A99­ 216031, NE 3001, U96-2408, Colfax), and four were tolerant to BPMV (PI 184042, M93-326056, M95-255017, Spansoy 201). Treatment of seed with the insecticide imidacloprid (1-[(6-chloro-3-pyridinyl)­ methyl]-N-nitro-2-imidazolidinimine) did not effect disease control. The relative level of virus antigen in seed harvested from experimental plots was shown to correlate significantly with virus incidence in plots. The data suggest that quantitative assay of virus seed antigen may provide a useful estimate of relative virus incidence in test plots and aid identification of field tolerance to seed-borne viruses.

Two new flavones, 5-hydroxy-8-hydroxymethyl-7,4′-dimethoxy-flavone (1) and 6-hydroxy-8-hydroxymethyl-7,4′-dimethoxy-flavone (2), together with six known flavones (3–8), were isolated from the bark of Lindera caudata. The structures of 1–8 were elucidated by spectroscopic methods including extensive 1D and 2D NMR techniques. Compounds 1–8 were evaluated for their anti-tobacco mosaic virus (anti-TMV) activity. The results showed that Compounds 1 and 2 showed high anti-TMV activity with inhibition rates of 31.2 and 28.8%, respectively. These values are close to those of positive control.

Wheat (Triticum aestivum L.) yellow mosaic virus (WYMV) is transmitted by a fungal vector through soil and causes serious wheat yield losses due to yellow mosaic disease, with yellow-streaked leaves and stunted plants. In the present study, the amplified fragment length polymorphisms (AFLP) and simple sequence repeat (SSR) were used to identify the molecular linkages with the resistance gene against WYMV. Bulked segregant analysis was performed with an F2 population derived from the cross of cultivar Ningmai 9 (resistant) × cultivar Yangmai 10 (susceptible). By screening among the resistant or susceptible parents, the F2 pools and the individuals in the F2 population with 64 combined selective AFLP primers (EcoRI/MseI) or 290 reported SSR primers, a polymorphic DNA segment (approximately 120 bp) was amplified using the primer pair E2/M5, and an SSR marker (approximately 180 bp) was located on wheat chromosome 2 A using the primer Xgwm328. Analysis with MAPMAKER/Exp Version 3.0b (Whitehead institute for Biomedical Research, Cambridge, MA, USA) indicated that these two markers were dominantly associated with the resistance gene at distances of 5.4 cM or 17.6 cM, respectively. The resistance gene to WYMV derived from Ningmai 9, is temporarily named YmNM, and was mapped to wheat chromosome 2A. (Managing editor: Li-Hui ZHAO)

Surveys were conducted during the cool-dry months of June-August 1997 and June-July 1998 for the presence of viruses in irrigated wheat in Central, Copperbelt, Lusaka and Southern Provinces of Zambia in 14 commercial farms and four wheat cultivar plots. Virus symptoms were observed on nine wheat cultivars (Triticum aestivum 'Deka', 'Gamtoos', 'Lorie II', 'MM2', 'Nata', 'Nkwazi', 'P7', 'Scan' and 'Sceptre') of South African, Zambian and Zimbabwean origin. Several viruses were identified on the basis of field symptomatology, symptoms developing on mechanically inoculated indicator plant species or cultivars and serology (DAS-ELISA). The study revealed the occurrence ofBrome mosaic virus (BMV), Barley stripe mosaic virus (BSMV), Barley yellow dwarf virus and its strains (BYDV-PAV and RPV), Soil-borne wheat mosaic virus (SBWMV), Wheat dwarf virus (WDV), Wheat streak mosaic virus (WSMV) and Wheat spindle streak mosaic virus (WSSMV). DSA-ELISA tests confirmed these identifications. The prevalence of viruses varied annually and from field to field. BSMV, BYDV-PAV, SBWMV, WDV, WSMV and WSSMV were found to be the most prevalent viruses. Viruses generally occurred in mixed infections of 3-6 viruses and the most common virus complex consisted of 4 viruses (50%), viz. BYDV, SBWMV, WDV and WSSMV. Five- and six-virus complexes were relatively less common (20% each) whereas 3-virus complex was noticed in only 10% cases. SBWMV and WSSMV have been found to be new to Africa and Zambia and are reportedly vectored by a fungal protist -Polymyxa graminis. BYDV strains MAV and SGV were also tested but gave negative results against their antisera.

Summary Purified Tomato leaf curl Bangalore virus (ToLCBV) was injected into mice and the splenocytes were used for establishing hybridoma lines. Initial screening of culture supernatants showed that 13 lines produced antibody, and after further screening four produced functional monoclonal antibodies. Upon characterisation, these were found to be of low affinity, probably due to host protein contamination and poor yield of native virus in the original preparations. In order to circumvent these problems, the coat protein of ToLCBV was over-expressed in Escherichia coli. Fusion experiments using recombinant coat protein as antigen yielded two primary hybridoma clones G 11 and E4 that exhibited good affinity of binding to the antigen. Sub-cloning yielded four monoclonal antibodies G 11 E 7 E 7, G 11 E 7 G 12, E 4 E 2 and E 4 G 6 . G 11 E 7 E 7 and G 11 E 7 G 12 successfully detected ToLCBV in infected leaf extracts of tomato and Nicotiana benthamiana, viruliferous whiteflies and weed samples. These monoclonal antibodies could also detect other type III geminiviruses such as Pumpkin yellow vein mosaic virus and Bhendi yellow vein mosaic virus. Thus these monoclonal antibodies can be used for testing field-collected samples.

Several wheat genotypes, including eight with known field responses, were evaluated for their reaction to Soil-borne cereal mosaic virus (SBCMV, genus Furovirus) by growing in naturally infested soil under controlled environment conditions. Virus antigen titres in the foliage 8–9 weeks after sowing mostly reflected the field responses, showing that growth chamber-based tests can be used to improve the speed and reliability of germplasm screening. Such tests were used to determine the mode of inheritance of the SBCMV resistance in cv. Cadenza, commonly used in UK wheat-breeding programmes. One hundred and eleven doubled haploid (DH) lines derived from an F1 of a cross between cvs Cadenza (resistant) and Avalon (susceptible) were evaluated. This DH population segregated for the reaction to SBCMV in a ratio of 1 : 1 (resistant : susceptible). This suggests that the SBCMV resistance is controlled by a single gene locus. As a first step towards identification of new sources of improved SBCMV resistance (e.g. immunity) as well as sources of the resistance to the virus vector, Polymyxa graminis, a set of 26 Triticum monococcum lines of diverse geographical origin was also screened. Most lines were susceptible to SBCMV, but one line of Bulgarian origin was resistant to the virus and possibly partially resistant to the virus vector.

There are claims that at least 11 genes confer resistance in barley (Hordeum vulgaris) to one or more components of the soilborne barley mosaic virus complex but, apart from the immunity conferred by the widely used gene rym4, little is known about their mode of action. This study used mechanical (sap) and plasmodiophorid vector-inoculation techniques combined with ELISA, RT-PCR, symptom development and virus transmission to investigate the response of different genotypes to Barley mild mosaic virus (BaMMV). Barley genotypes were grown at 20 and 12°C to test for temperature sensitivity. Plants with the genes rym3 or rym6 were fully susceptible to the virus, whereas those with genes rym1, Rym2, rym5 or rym11 appeared to be immune, as BaMMV was never detected in any tissue type nor was the virus transmitted from them to susceptible genotypes. The remaining genotypes could all be infected to some extent by BaMMV using one or both inoculation methods, and virus could be transmitted from their roots by the plasmodiophorid vector Polymyxa graminis. Plants with the rym7 gene had delayed symptoms compared to susceptible controls at 12°C. Plants with the rym8 gene could be infected by both inoculation methods, but there was no virus in the leaves at 12°C. Plants with the rym9 gene could be infected only by vector inoculation, and virus remained localized in the roots. Plants with the rym10 gene appeared susceptible by mechanical inoculation at both temperatures, but after vector inoculation virus moved to leaves only at 20°C. This suggests the operation of translocation resistance in plants with the rym8, rym9 or rym10 genes, which is temperature-sensitive in rym8 and rym10 and perhaps tissue-specific in rym9. No resistance to P. graminis was observed in any of the genotypes.

SUMMARY Transgenic peas containing a copy of the Pea seed-borne mosaic virus (PSbMV) isolate DPD1 NIb sequence develop a 'recovery' phenotype when challenged with either the homologous (DPD1) or a heterologous (NY) PSbMV isolate. However, the specificity of the subsequent resistance differs with respect to the initiation by and targeting of different virus isolates. Analysis of tissue in which recovery had been induced by either of the isolates, revealed the presence of low molecular RNA molecules (siRNA) derived from degradation of the NIb transgene mRNA. When non-transgenic scions were grafted on to transgenic stocks in which recovery had been induced, all the scions became infected, indicating that the virus can be exported from recovered tissue. Experiments in which recovered scions were grafted on to non-transgenic stocks revealed that the recovery phenotype could be maintained in the apparent absence of a source of virus. However in a number of cases, side-shoots which developed on the non-transgenic stock became infected. These results indicate that recovered tissue contains extremely low levels of infectious virus with the potential, directly or indirectly, to confer the observed resistance specificity. Indirectly, the viral genome could act as a source of specific siRNA molecules, which are present in infected tissues but are below the level of detection in recovered tissues. These could act in conjunction with siRNAs derived from the transgene mRNA to maintain a level of PTGS (post-transcriptional gene silencing) activity which is effective in preventing further accumulation of homologous or related viruses. We suggest a model to explain the differential specificity.

Yellow vein mosaic disease symptoms occur frequently in pumpkin in India. Diseased plants show vein yellowing, which sometimes coalesces to form chlorotic patches. Infected plants are stunted and flowers drop prematurely, greatly reducing yields. Diseased plants are infected by a begomovirus, designated pumpkin yellow vein mosaic virus (PYVMV), which is transmitted readily and in a persistent manner by the whitefly, Bemisia tabaci. Transmission of PYVMV requires minimum acquisition and inoculation access periods of 30 min and 10 min, respectively. The minimum latent period in the insect is 6 h and the virus persists in the vector for at least 8 days. PYVMV has a narrow host range consisting of a small number of cucurbit species and some tobacco cultivars. It was detected serologically in diseased plants and in viruliferous B. tabaci using polyclonal antibodies in a double-antibody sandwich enzyme-linked immunosorbent assay. Reactions with monoclonal antibodies in a triple-antibody sandwich ELISA showed that PYVMV has an epitope profile distinct from those of other begomoviruses from the Indian sub-continent. Polymerase chain reaction amplified fragments from the putative viral coat and movement protein genes. Based on comparative phylogeny of complete coat protein gene sequences, PYVMV was most similar to to the bipartite Tomato leaf curl New Delhi virus from India and appears to be a new strain of this virus.

SUMMARY Taxonomy: Alfalfa mosaic virus (AMV) is the type species of the genus Alfamovirus and belongs to the family Bromoviridae. In this family, the tripartite RNA genomes of bromo-, cucumo- and probably oleaviruses are infectious as such, whereas infection with the three genomic RNAs of alfamo- and ilarviruses requires addition to the inoculum of a few molecules of coat protein (CP) per RNA molecule. RNAs 1 and 2 encode the replicase proteins P1 and P2, RNA 3 encodes the movement protein and CP. CP is translated from the subgenomic RNA 4. Physical properties: RNAs 1 (3.65 kb), 2 (2.6 kb) and 3 (2.2 kb) are separately encapsidated into bacilliform particles which are 19 nm wide and 35–56 nm long. In addition, the virus preparations contain spheroidal particles each containing two copies of RNA 4 (0.88 kb). Virus particles contain 16–17% RNA and are mainly stabilized by protein–RNA interactions. The 3′-termini of the viral RNAs contain a homologous sequence of 145 nucleotides that can adopt two alternative conformations: one represents a high-affinity binding site for CP, the other resembles a tRNA-like structure and is required for minus-strand promoter activity. Hosts: AMV mostly infects herbaceous plants, but several woody species are included in the natural host range. The experimental and natural host ranges include over 600 species in 70 families. At least 15 aphid species are known to transmit the virus in the stylet-borne or non-persistent manner. Economic importance: AMV is a significant pathogen in alfalfa and sweet clover and can spread from these forages to neighbouring crops like pepper, tobacco or soybean. The recent introduction of the soybean aphid (Aphis glycines) in the mid-west states of the USA has increased the incidence of AMV in soybean. AMV occurs world-wide in potato and is referred to as ‘calico mosaic’ because of its characteristic symptoms on the foliage. However, the economic importance of AMV in potato is limited. Useful websites: review paper; host range and physical properties; structural information.

Pigeonpea sterility mosaic virus (PPSMV) is transmitted by the eriophyid mite, Aceria cajani, and is very closely associated with sterility mosaic disease (SMD) of pigeonpea (Cajanus cajah) in the Indian subcontinent. Antiserum produced to purified PPSMV preparations detected a virus-specific 32 kDa protein in sap of SMD-affected pigeonpea plants by ELISA and Western blotting. PPSMV was transmitted mechanically in sap of SMD-affected pigeonpea leaves to Nicotiana benthamiana. Ultrastructural studies of symptom-bearing leaves of two pigeonpea cultivars, (ICP8863 and ICP2376) and N. benthamiana infected with PPSMV, detected quasi-spherical, membrane bound bodies (MBBs) of c. 100–150 nm and amorphous electron-dense material (EDM). These structures were distributed singly or in groups, in the cytoplasm of all cells, except those in conductive tissues. Fibrous inclusions (FIs), composed of randomly dispersed fibrils with electron lucent areas, were present in the cytoplasm of palisade cells and rarely in mesophyll cells of the two pigeonpea cultivars but were not detected in infected TV. benthamiana plants. In the PPSMV-infected pigeonpea cultivars and TV. benthamiana, immuno-gold labelling, using antiserum to PPSMV, specifically labelled the MBBs and associated EDM, but not the FIs. The MBBs and associated inclusions are similar in appearance to those reported for plants infected with the eriophyid mite-transmitted High Plains virus and the agents of unidentified aetiology associated with rose rosette, fig mosaic, thistle mosaic, wheat spot chlorosis and yellow ringspot of budwood. The nature of these different inclusions is discussed

Geminiviruses have spread worldwide and have become increasingly important in crop plants during recent decades. Recombination among geminiviruses was one major source of new variants. Geminiviruses replicate via rolling circles, confirmed here by electron microscopic visualization and two-dimensional gel analysis of Abutilon mosaic virus (AbMV) DNA. However, only a minority of DNA intermediates are consistent with this model. The majority are compatible with recombination-dependent replication (RDR). During development of naturally infected leaves, viral intermediates compatible with both models appeared simultaneously, whereas agro-infection of leaf discs with AbMV led to an early appearance of RDR forms but no RCR intermediates. Inactivation of viral genes ac2 and ac3 delayed replication, but produced the same DNA types as after wild-type infection, indicating that these genes were not essential for RDR in leaf discs. In conclusion, host factors alone or in combination with the viral AC1 protein are necessary and sufficient for the production of RDR intermediates. The consequences of an inherent geminiviral recombination activity for the use of pathogen-derived resistance traits are discussed.

Summary Taxonomy: Tobacco mosaic virus (TMV) is the type species of the Tobamovirus genus and a member of the alphavirus-like supergroup. Historically, many tobamoviruses are incorrectly called strains of TMV, although they can differ considerably in sequence similarities and host range from each other and from TMV. Physical properties: TMV virions are 300 × 18 nm rods with a central hollow cavity (Fig. 1) and are composed of 95% capsid protein (CP), and 5% RNA. Each CP subunit interacts with 3-nts in a helical arrangement around the RNA. Virions are stable for decades; infectivity in sap survives heating to 90 °C. Figure 1. Electron micrograph of TMV virions stained with uranyl acetate. Courtesy of Dr J.N. Culver, University of Maryland Biotechnology Institute. Download figure to PowerPoint Hosts: The natural host range of TMV is limited; however, a broad range of weed and crop species, mostly Solanaceae that includes tobacco, pepper and tomato can be infected experimentally [Holmes, F.O. (1946) A comparison of the experimental host ranges of tobacco etch and tobacco mosaic viruses. Phytopathology, 36, 643–657]. TMV distribution is worldwide. No biological vectors are known. Useful website: http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/71010001.htm

An outline is given of results for the transfer of new resistances against leaf rust and barley mosaic viruses from Hordeum bulbosum into winter barley. Progenies from backcrosses of barley cultivars with H. bulbosum hybrids were tested both in conventional breeding trials and in additional tests under controlled conditions. Resistance to both pathogens proved to be stable and of good heritability, with differences occurring which depended on the combinations used. Lines with resistance to all leaf rust and mosaic viruses tested, or to either one, were selected. Both resistances segregated independently.

Summary A yam potyvirus was isolated from Dioscorea alata samples collected in Nigeria. The virus was not transmissible mechanically but was transmitted by Aphis craccivora to four cowpea cultivars (Ife Brown, IT84S-2114, IT82E-10 and TVu2657), and from which it could be mechanically transmitted between the cowpea cultivars. In infectivity- tests using cowpea extracts, the virus had a dilution end point of 10-4, a thermal inactivation point of 60–65°C and longevity in vitro of 2 days at room temperature. The virus coat protein had an estimated molecular weight of 32 100 daltons. The virus was identified as an isolate of Dioscorea alata virus (DAV; syn. yam virus 1) due to its biological characteristics and its serological reaction with antiserum raised against DAV. The virus is not related to yam mosaic virus, but distantly related to blackeye cowpea mosaic virus and cowpea aphid-borne mosaic virus.

The present work describes the identification and characterization of a potyvirus isolated from siratro (Macroptilium atropurpureum Urb.) in the north-west region of the State of Sao Paulo, Brazil. The virus was transmitted by mechanical inoculation. Its host range was restricted mainly to members of the Fabaceae. A cDNA fragment of about 930 bp was amplified by RT/PCR, cloned and sequenced. The fragment, which included the coat protein gene, had amino acid identity percentages between 88 and 98% with isolates of Bean common mosaic virus (BCMV). Phylogenetic analysis grouped the siratro potyvirus and BCMV isolates in 99% of the replicates, including Azuki mosaic virus, Dendrobium mosaic virus, Blackeye cowpea mosaic virus and Peanut stripe virus, which have been classified as BCMV strains. This is the first citation on the presence of BCMV in siratro plants in Brazil.

Summary. Symptoms associated with infection by Omithogalum mosaic virus (OMV) were documented among horticulturally important Omithogalum spp. grown in commercial greenhouses and open fields in Israel. OMV was mechanically transmitted to Chenopodium quinoa and C. amaranticolor. The virus was purified from infected C. quinoa using CsCl step gradient centrifugation. Virus yield of 18–24 mg kg“1 were obtained. Antiserum produced to the purified virus was highly specific in immunoblots and immunosorbent electron microscopy. Reverse transcription - polymerase chain reaction (RT-PCR) utilising potyvirus-specific primers and the viral RNA resulted in the amplification of a DNA product of 1275 nucleotides. This PCR product was cloned and sequenced; it encoded an open reading frame of 333 codons and a 3‘ non-coding region of 275 nucleotides. Analysis of the amino acid sequences of the putative CP of the Israeli isolate of OMV showed 95% similarities to the South African isolate.

Monocyclic components (development rate during the incubation period or latent period, lesion density, lesion size and disease severity) of rust (Uromyces appendiculatus) and of angular leaf spot (Phaeoisariopsis griseola) in two bean (Phaseolus vulgaris) cultivars (Rosinha G-2 and Carioca), pre-infected or not with bean line pattern mosaic virus (BLPMV), were determined. Trials were conducted at temperatures in the range from 9 to 27°C for rust and from 12 to 30°C for angular leaf spot. Regardless of viral pre-infection, the effect of temperature on the four monocyclic components followed an optimum curve and could be described by a generalized beta function. Generally, angular leaf spot was favoured by higher temperatures with an optimum for disease severity between 24.2 and 28.3°C compared with 15.9–18.5°C for rust. Pre-infection with BLPMV did not change the shape of the optimum curves for all components, but significantly reduced lesion density and disease severity on both cultivars. The development rates during incubation and latent periods for both fungal diseases were not affected by BLPMV. Pre-infection with virus did not alter the ranking of cultivars with respect to resistance to both fungal diseases.

Summary A panel of 25 monoclonal antibodies (MAbs) raised against particles of two heterologous whitefly-transmitted geminiviruses (begomoviruses) was used in triple antibody-sandwich ELISA (TAS-ELISA) to determine the detectability and epitope profiles of 26 Indian isolates of tobacco leaf curl virus (TLCV) and 13 of croton yellow vein mosaic virus (CYVMV). Stock cultures of the two viruses had indistinguishable epitope profiles although they differ in symptomatology and particle stability. Their epitope profiles also strongly resembled those of Indian isolates of bhendi (okra) yellow vein mosaic and Indian cassava mosaic (ICMV) viruses. TLCV isolates from Andhra Pradesh, Gujarat and Karnataka States differed slightly in epitope profile: they reacted with at least eight out of 10 MAbs raised to ICMV but only one to four out of 15 MAbs raised to African cassava mosaic virus (ACMV). Virus isolates serologically indistinguishable from TLCV were detected in symptom-bearing weeds (Acanthospermum hispidum, Ageratum conyzoides, Euphorbia geniculata, Parthenium hysterophorus) found in leaf curl-affected tobacco fields and shown previously to be experimental hosts of TLCV. Indian TLCV isolates had small, consistent differences in epitope profile from Pakistani isolates but large differences from isolates from Burkina Faso, Malawi or Uganda. Isolates from the three African countries reacted with four or five of the ACMV MAbs but only one or two of the ICMV MAbs, and there were small but consistent inter-country differences. CYVMV isolates from three Indian States showed less epitope variation than did Indian isolates of TLCV. TAS-ELISA with MAb SCR 18 was a more sensitive test for detecting Indian TLCV isolates than was double antibody-sandwich ELISA with polyclonal antibodies.

'Endurance' hard red winter wheat was released to certified seed growers with permission of the Oklahoma Agricultural Experiment Station and the USDA-ARS in 2004. This cultivar is derived from the three-way cross HBY756A/'Siouxland'//'2180'. Its name derived from the unique ability to endure and recover from extended and intensive grazing in a dual-purpose management system common to Oklahoma and surrounding states. Endurance is a moderately tall semidwarf wheat with late arrival to first-hollow-stem stage and intermediate maturity. It is resistant to leaf rust (Puccinia triticina [P. recondita]) and moderately resistant to stripe rust (P. striiformis) and Wheat soilborne mosaic virus. Endurance is adapted to the irrigated and dryland production areas throughout the southern Great Plains.

Summary The severity and persistence of symptoms of mosaic virus disease were monitored during the first six months of two growing seasons in cassava of the African cassava mosaic virus (ACMV)-resistant cv. TMS 30572 either inoculated by grafting with a mild or severe strain or infected from the planted cutting. Symptomless shoots developed between January and March 1995 in two field trials differing in age by c. 6 months; this recovery occurred during particularly hot weather. Recovery was often only temporary in the plants inoculated with the severe strain and occurred later compared with those inoculated with the mild. In 1996, the weather was cooler and recovery that year was delayed until flowering, c. 7 months after planting, when recovered shoots were often produced from buds in the axils of symptomless leaves produced amongst diseased leaves. Most cuttings taken from the upper parts of diseased plants produced symptomless (reverted) progenies whereas most cuttings taken from the base of diseased plants produced diseased progenies. Reversion seemed to be associated with the recovery that had already occurred in the upper stems of the parent plants.

Potato viruses are prevalent worldwide and cause substantial economical losses in the potato crop (Solanum tuberosum L.). Therefore, various types of resistance to potato viruses identified in cultivated and wild potato species are used in potato breeding programs and are briefly reviewed in this paper. However, the current nomenclature of virus resistance specificities is confusing because it was adopted at an earlier time when several virus strain groups were believed to represent individual virus species and because it does not distinguish between strain-specific and comprehensive resistance specificities. A consistent nomenclature is desirable to distinguish both currently known virus resistances and any novel virus resistances detected in the future. A descriptive and systematic nomenclature for resistance specificities is proposed which denotes (1) type of resistance (2) identity of virus (3) the virus strain group(s) against which the resistance is effective (4) the virus strain group(s) against which the resistance is not effective, and (5) the potato species in which the resistance is described.

The 3' terminal region of the genomic RNA of a potyvirus isolated from Brachiaria spp. which is related to guinea grass mosaic virus (GGMV), was compared to that of members of the sugarcane mosaic subgroup of poty viruses. Reverse transcription-polymerase chain reaction (RT-PCR) of total nucleic acid extracted from infected B. brizantha resulted in the amplification of a DNA product of c. 0.9 kb. This product was cloned and sequenced; it has an open reading frame of 149 amino acid residues, and a 3' untranslated region (UTR) of 474 nucleotides. Optimal alignments of the 3' UTRs of the Brachiaria potyvirus and members of the sugarcane mosaic subgroup of potyviruses showed that it has nucleotide sequence similarities of c. 42, 46, 46, and 46% to maize dwarf mosaic virus strain A, sugarcane mosaic virus strains SC and MDB, and sorghum mosaic virus strain SCH, respectively. It had higher nucleotide sequence similarities of c. 88, 89, and 92% with Johnsongrass mosaic virus (JGMV) strains MDO, MDKSI and JG, respectively. Analyses of the deduced amino acid sequence of the Brachiaria potyvirus coat protein fragment revealed a 97.3% similarity to the JG strain of JGMV to which it is serologically related. We propose that the Brachiaria potyvirus now be considered a strain of JGMV (designated JGMV-Brac).

The occurrence of cucumber mosaic (CMV) and tomato spotted wilt (TSWV) viruses in the main vegetable producing regions of northeastern Spain was studied during the growing seasons of 1992 and 1993, by sampling in July and September. Both viruses were found widely distributed in field tomato crops and surrounding weeds. Coastal areas were the most affected by both CMV and TSWV, whereas inland TSWV was nearly absent. Higher levels of infection were found in autumn for TSWV in tomato crops and weeds, and for CMV in tomatoes. From the 51 weed species of 19 families collected, 25 species were found infected with CMV and 15 with TSWV. Among them, Convolvulus arvensis, Malva sylvestris and Sonchus tenerrimus could be of special importance as local reservoirs; commonly associated with tomato crops, they were infected quite frequently with CMV and/or TSWV, and being perennial, could maintain the viruses between cropping seasons.