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The cotton leafroll dwarf virus (CLDV), an important viral pathogen responsible for substantial losses in cotton crops, has recently emerged in the United States (US). Although CLDV shares similarities with other members of the genus Polerovirus in terms of encoded proteins, their functional characteristics remain largely unexplored. In this study, we expressed and analyzed each protein encoded by CLDV to determine its intracellular localization using fluorescence protein fusion. We also evaluated their potential to induce plant responses, such as the induction of hypersensitive response-like necrosis and the generation of reactive oxygen species. Our findings show that the proteins encoded by CLDV exhibit comparable localization patterns and elicit similar robust plant responses as observed with cognate proteins from other viruses within the genus Polerovirus. This study contributes to our understanding of the functional repertoire of genes carried by Polerovirus members, particularly to CLDV that has recently emerged as a widespread viral pathogen infecting cotton in the US. [ABSTRACT FROM AUTHOR]

Crocus sativus L. leaf samples were serologically tested for the presence of beet western yellows virus (BWYV) and 17.6% of samples showed positive reaction. The partial genome sequence of the BWYV isolate-Saf-Th16 from saffron was closely related to that of BWYV isolates from citron in the USA. This is the first report of BWYV on saffron plants from Iran. [ABSTRACT FROM AUTHOR]

This article reports the first case of Pod pepper vein yellows virus (PoPeVYV) infecting Solanum nigrum L. plants in China. PoPeVYV is a polerovirus that causes pepper vein yellows disease in peppers, leading to symptoms such as interveinal leaf yellowing and curling. The researchers extracted RNA from diseased plants and used reverse transcription PCR to confirm the presence of PoPeVYV. The amplicons obtained showed high nucleotide identity with a PoPeVYV isolate from Yunnan Province. This study provides important information about the spread of PoPeVYV and its impact on Solanum nigrum L. plants in China. [Extracted from the article]

Two near complete polerovirus genomes were assembled using high throughput sequencing (HTS) data from two separate samples of garlic cultivar 'Glenlarge' grown in Gatton, Queensland, Australia. Whole genome sequence comparisons showed that one contig shared 96.7% nucleotide identity with phasey bean mild yellows virus (MT966032.1) and the other, 99.8% nucleotide identity with turnip yellows virus (MT586581.1). Phylogenetic analyses further revealed that the isolates fell within the PBMYV group 2 and TuYV group 2 clades, respectively. This is the first report of these poleroviruses infecting garlic. [ABSTRACT FROM AUTHOR]

Transcriptome datasets available in public domain serve as valuable resource for identification and characterization of novel viral genomes. Poleroviruses are economically important plant-infecting RNA viruses belonging to the family Solemoviridae. In the present study, we explored the plant transcriptomes available in public domain and identified five putative novel poleroviruses tentatively named as Foeniculum vulgare polerovirus (FvPV), Kalanchoe marnieriana polerovirus (KmPV), Paspalum notatum polerovirus (PnPV), Piper methysticum polerovirus (PmPV), Trachyspermum ammi polerovirus (TaPV) and a novel enamovirus named as Celmisia lyallii enamovirus (ClEV) in Foeniculum vulgare, Kalanchoe marnieriana, Paspalum notatum, Piper methysticum, Trachyspermum ammi and Celmisia lyallii, respectively. Coding-complete genomes (5.56–5.74 kb) of CIEV, KmPV, PnPV, PmPV and TaPV were recovered while only the partial genome of FvPV could be recovered. The genome organization of identified viruses except ClEV is 5'–ORF0–ORF1–ORF2–ORF3a–ORF3–ORF4–ORF5–3' while that of ClEV is 5'–ORF0–ORF1–ORF2–ORF3–ORF5–3'. Phylogenetic analysis revealed that poleroviruses of apiaceous plants formed a monophyletic clade within the genus Polerovirus. [ABSTRACT FROM AUTHOR]

Cotton bunchy top disease causes sporadic but serious losses in cotton (Gossypium hirsutum) in Australia but little has been reported about the diversity, distribution, host range and detection of the causal agent, cotton bunchy top virus (CBTV). We have obtained the complete coding sequence of two poleroviruses from symptomatic cotton to cover all seven putative open reading frames. These species are called CBTV-1 and CBTV-2 and all seven predicted gene products differ by 25% to 49% amino acid identity, indicating they are distinct polerovirus species. A multiplex PCR for CBTV-1 and CBTV-2 was used to screen more than 700 plant samples from 36 species to identify 16 new field and experimental host species. Serological detection by tissue blot immune assay was successful when the two viruses were transmitted to chickpea (Cicer arietinum), but was unreliable for detecting the viruses in cotton. Volunteer and ratoon cotton were identified as common reservoirs of CBTV nearby to cotton cropping areas. Other species that may be regionally important reservoirs include Malva parviflora, Euphorbia hirta and Gossypium sturtianum. Both CBTV species were common and widespread in all major cotton production regions and the genetic diversity within each species was low for the genome region spanning from the 3' end of open reading frame (ORF) 2 and complete ORF 3. From a total of 257 cotton plants displaying symptoms typical of cotton bunchy top, 256 (99.6%) were positive for CBTV-2 and 93 of these (36%) were mixed infections of CBTV-2 and CBTV-1. As a single infection, CBTV-1 was non-symptomatic, indicating that CBTV-2 is the causal agent of typical cotton bunchy top disease. [ABSTRACT FROM AUTHOR]

Maize yellow mosaic virus (MaYMV) is a single-stranded RNA polerovirus first identified in China. MaYMV was recently reported from West and East Africa, however it had not yet been reported from southern Africa. RNA-seq data from South African field-grown fungal-infected maize was mined for viral sequences by de novo assembly of reads that did not map to the maize or fungal genomes. Predicted proteins from the de novo-assembled unmapped reads matched MaYMV proteins with regions of 96–100% identity. MaYMV was detected in maize RNAseq data from 2009, 2012 and 2013. Complete South African MaYMV genome sequences (5642 nt) were determined by RT-PCR and Sanger sequencing of samples from two different maize genotypes, years, and sites. Phylogenetic analysis confirmed the species identity as MaYMV, and showed separate clustering of isolates between Africa, Asia and South America. Some MaYMV positive samples had reads matching Potyviridae (Johnson grass mosaic virus and Sugarcane mosaic virus), and mycoviruses (Setosphaeria turcica hypovirus 1, Bipolaris maydis partitivirus 1, and Pleospora typhicola fusarivirus 1). A 2016/2017 RT-PCR survey of maize plants exhibiting virus-like symptoms, such as yellowing and streaking patterns, revealed MaYMV in 39 samples from six provinces in South Africa. This report documents the earliest known MaYMV infection world-wide, and indicates that the virus is widespread throughout Africa. [ABSTRACT FROM AUTHOR]

Three novel viruses were detected from Japanese persimmon 'Reigyoku' (Diospyros kaki), which grows poorly when top-grafted onto some interstocks. The genomic characterization and the phylogenetic analysis of these viruses indicated that they are likely new members of the genera Ampelovirus, Polerovirus, and Waikavirus, tentatively named Persimmon ampelovirus (PAmpV), Persimmon polerovirus (PPolV), and Persimmon waikavirus (PWaiV). The alignment of two PAmpV variants with Plum bark necrosis stem pitting–associated virus isolates had 72.5%–79.0% amino acid sequence identities with RNA-dependent RNA polymerase, 71.6%–79.2% with a heat shock protein 70 homolog, and 66.2%–69.8% with coat protein, respectively. Two PPolV variants showed the highest amino acid sequence identities (46.6%) with the P1–P2 fusion protein of Brassica yellows virus. PWaiV had the highest amino acid sequence identity (41.9%) with the conserved domain between proteinase and polymerase of Rice tungro spherical virus. Reverse-transcription and polymerase chain reaction detected Persimmon virus A, Apple crinkle fruit viroid, and Citrus viroid VI from the mother clone with good growth, and PAmpV, PPolV, and Persimmon latent viroid (PLVd) additionally from 20 trees with poor growth. PAmpV, PPolV, and PLVd were detected from four, 10, and 10 of 14 trees with good growth, respectively, and the grafting of budwood harboring these three pathogens caused significant stunt in mother clones. [ABSTRACT FROM AUTHOR]

Chlorosis and yellowing with green-vein banding on older leaves were observed in surveys of cultivated cucumber fields in 2016 in Java, Indonesia. Initial dot immuno-binding assays detected seven different viruses varying in frequency among over 500 samples from 27 locations. Cucurbit aphid-borne yellows virus (CABYV) was detected at a frequency approaching 100% in four provinces in Java. The coat protein nucleotide and amino acid sequences of four isolates had highest identity with that of CABYV isolate Aileu in East Timor. This is the first report of CABYV infection of cucumber in Indonesia. [ABSTRACT FROM AUTHOR]

This article reports the first occurrence of the cucurbit aphid-borne yellows virus (CABYV) infecting Indian round gourd (Praecitrullus fistulosus) in India. The virus causes yellowing, interveinal chlorosis, and thickening of mature leaves in affected plants. The study used Enzyme Linked Immunosorbent Assay (ELISA) and RT-PCR assays to confirm the presence of CABYV in symptomatic plants, while asymptomatic plants tested negative for all viruses. The sequence of the virus obtained from the study was found to be closely related to other CABYV isolates. This finding suggests that CABYV poses a potential threat to cucurbit cultivation in India. [Extracted from the article]

In Western Australia (WA) viruses belonging to the Luteoviridae have been identified infecting crops, including Barley yellow dwarf virus, Cereal yellow dwarf virus, Phasey bean mild yellows virus, Potato leaf roll virus, and Turnip yellows virus (TuYV). It is thought there are other viruses of the Luteoviridae in WA, however efforts to determine their presence have been greatly hindered by the very close serological relationship of many virus species within the Luteoviridae. Research on TuYV in Australia has predominantly been on canola (Brassica napus) but it has also been detected on other hosts. Between 2006 and 2014, virus isolates from a range of hosts and locations were obtained following serological testing using antisera for Beet western yellows virus (BWYV). Molecular characterisation using next generation sequencing (NGS) produced whole genome sequences of ten virus isolates with seven new TuYV and three Soybean dwarf virus (SbDV) genomes identified. In addition, biological studies of two TuYV isolates were done. We discuss the relationship of these ten new isolates within the Luteoviridae and determined BWYV not to be present in WA. [ABSTRACT FROM AUTHOR]

Brassica yellows virus (BrYV), prevalently distributed throughout mainland China and South Korea while triggering serious diseases in cruciferous crops, is proposed to be a new species in the genus Polerovirus within the family Luteoviridae. There are three distinct genotypes (BrYV-A, BrYV-B and BrYV-C) reported in cabbage and radish. Here, we describe a new BrYV isolate infecting tobacco plants in the field, which was named BrYV-NtabQJ. The complete genome sequence of BrYV-NtabQJ is 5741 nt in length, and 89% of the sequence shares higher sequence identities (about 90%) with different BrYV isolates. However, it possesses a quite divergent region within ORF5, which is more close to Beet western yellows virus (BWYV), Beet mild yellowing virus (BMYV) and Beet chlorosis virus (BChV). A significant recombination event was then detected among BrYV-NtabQJ, BrYV-B Beijng isolate (BrYV-BBJ) and BWYV Leonurus sibiricus isolate (BWYV-LS). It is proposed that BrYV-NtabQJ might be an interspecific recombinant between BrYV-BBJ and BWYV-LS, and the recombination might result in the successful aphid transmission of BrYV from cruciferous crops to tobacco. And it also poses new challenges for BrYV diagnosis and the vegetable production. [ABSTRACT FROM AUTHOR]

These symptoms resemble those caused by an aphid-borne polerovirus (cucurbit aphid-borne yellows virus, CABYV) and three whitefly-transmitted criniviruses (beet pseudo-yellows virus, BPYV; cucurbit yellow stunting disorder virus, CYSDV; cucurbit chlorotic yellows virus, CCYV). Keywords: Polerovirus; CABYV; Cucumber; Albania EN Polerovirus CABYV Cucumber Albania 367 368 2 03/16/23 20230201 NES 230201 During autumn 2021, a limited survey was conducted for viruses in cucumber crops in Albania. References 1 Knierim D, Deng TC, Tsai WS, Green SK, Kenyon L. Molecular identification of three distinct Polerovirus species and a recombinant Cucurbit aphid-borne yellows virus strain infecting cucurbit crops in Taiwan. [Extracted from the article]

Maize yellow dwarf virus-RMV2 (MYDV-RMV2) causes dwarfing and yellowing symptoms on leaves in field-grown maize plants in Anhui province in China. Herein, we evaluated the RNA silencing suppressor (RSS) activity of the P0 protein from MYDV-RMV2 by co-infiltration assays using wild-type and GFP-transgenic Nicotiana benthamiana (line 16C). The P0 of MYDV-RMV2 exhibited RSS activity and inhibited RNA silencing both locally and systemically. MYDV-RMV2 P0 acts as an F-box-like motif, and mutations to Ala at positions 67, 68, and 81 in the F-box-like motif (67LPxx81P) abolished the RSS activity of P0. However, MYDV-RMV2 P0 failed to interact with AGO1 from Arabidopsis thaliana. Expressing P0 induced developmental defects. P0 was targeted to both the nuclei and cytoplasm of plant cells. These findings expand our knowledge of the role of polerovirus P0 proteins in RNA silencing. [ABSTRACT FROM AUTHOR]

Since 2011-2012, Maize lethal necrosis (MLN) has emerged in East Africa, causing massive yield loss and propelling research to identify viruses and virus populations present in maize. As expected, next generation sequencing (NGS) has revealed diverse and abundant viruses from the family Potyviridae, primarily sugarcane mosaic virus (SCMV), and maize chlorotic mottle virus (MCMV) (Tombusviridae), which are known to cause MLN by synergistic co-infection. In addition to these expected viruses, we identified a virus in the genus Polerovirus (family Luteoviridae) in 104/172 samples selected for MLN or other potential virus symptoms from Kenya, Uganda, Rwanda, and Tanzania. This polerovirus (MF974579) nucleotide sequence is 97% identical to maize-associated viruses recently reported in China, termed ‘maize yellow mosaic virus’ (MaYMV) and maize yellow dwarf virus (MaYMV; KU291101, KU291107, MYDV-RMV2; KT992824); and 99% identical to MaYMV (KY684356) infecting sugarcane and itch grass in Nigeria; 83% identical to a barley-associated polerovirus recently identified in Korea (BVG; KT962089); and 79% identical to the U.S. maize-infecting polerovirus maize yellow dwarf virus (MYDV-RMV; KT992824). Nucleotide sequences from ORF0 of 20 individual East African isolates collected from Kenya, Uganda, Rwanda, and Tanzania shared 98% or higher identity, and were detected in 104/172 (60.5%) of samples collected for virus-like symptoms, indicating extensive prevalence but limited diversity of this virus in East Africa. We refer to this virus as “MYDV-like polerovirus” until symptoms of the virus in maize are known. [ABSTRACT FROM AUTHOR]

Overall, 244 samples of cucurbit crops with yellowing symptoms and selected weed species, from 15 provinces in Thailand, were screened by RT-PCR using primers Polero-CP-F and Polero-CP-R. A total of 160 samples (~66%) were infected by poleroviruses. Analysis of a 1.4 kb region covering the 3' RNA-dependent RNA polymerase (RdRp) gene, the intergenic non-coding region (iNCR), and the coat protein (CP), showed that four poleroviruses, namely, cucurbit aphid-borne yellows virus (CABYV), luffa aphid-borne yellows virus (LABYV), melon aphid-borne yellows virus (MABYV) and suakwa aphid-borne yellows virus (SABYV) were associated with the yellowing symptoms in cucurbit crops. Further analyses indicated presence of putative recombinant viruses referred to as CABYV-R and SABYV-R. CABYV-R was derived from the recombination between MABYV and the common strain of CABYV (CABYV-C). SABYV-R was derived from the recombination of MABYV and SABYV. [ABSTRACT FROM AUTHOR]

Occurrence of yellowing viruses (Beet pseudo-yellows virus, Cucurbit yellow stunting disorder virus and Cucurbit aphid-borne yellows virus) affecting cucurbits in Greece. Keywords: Polerovirus; CABYV; Muskmelon; Cucurbit; India EN Polerovirus CABYV Muskmelon Cucurbit India 383 383 1 03/16/23 20230201 NES 230201 Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/s42161-022-01302-z. [Extracted from the article]

Co-infection of Carrot red leaf virus (CtRLV), Carrot mottle virus (CMoV) and Carrot red leaf virus associated RNA (CtRLVaRNA) causes Carrot motley dwarf (CMD) disease. This study examined the capacity of the aphid Myzus persicae at transmitting viruses associated with CMD. M. persicae exposed to CMD-infected chervil plants transmitted CtRLV-, CMoV-and CtRLVaRNA to diseasefree chervil, fennel, celery, carrot, cilantro, and parsley, as shown by RT-PCR using specific primers. Recipient plants developed typical CMD symptoms. Sequence analysis of the amplified virus genes showed high sequence diversity with corresponding sequences available in GenBank. This study expands on Cavariella aegopodii, the only previously recognized aphid vector of CMD-causing viruses. [ABSTRACT FROM AUTHOR]

Although poleroviruses are known to infect a broad range of higher plants, carnivorous plants have not yet been reported as hosts. Here, we describe the first polerovirus naturally infecting the pitcher plant Nepenthes mirabilis. The virus was identified through bioinformatic analysis of NGS transcriptome data. The complete viral genome sequence was assembled from overlapping PCR fragments and shown to share 91.1 % nucleotide sequence identity with the US isolate of beet western yellows virus (BWYV). Further analysis of other N. mirabilis plants revealed the presence of additional BWYV isolates differing by several insertion/deletion mutations in ORF5. [ABSTRACT FROM AUTHOR]

Cotton bunchy top (CBT) is an aphid transmitted Polerovirus disease and a significant threat to the Australian cotton industry. Symptoms include stunted plant growth, and leaves often display pale green angular patterns at the leaf margins and dark green centers with a leathery texture. Resistance to CBT was evaluated in 206 F plants and 76 F families derived from the resistant cultivar 'Delta Opal' crossed to the susceptible cultivar 'Sicot 70', and in 25 other cultivars the majority susceptible to CBT. CBT resistance in 'Delta Opal' was shown to be controlled by a single dominant locus designated Cbt. A combination of AFLP and single nucleotide polymorphism markers located Cbt on chromosome A10, close to the mapped resistance locus in 'Delta Opal' to another Polerovirus disease of cotton; cotton blue disease. The markers identified flanking CBT resistance will provide useful tools for breeders for marker-assisted selection to alleviate the impact of this disease on cotton production. [ABSTRACT FROM AUTHOR]

Vegetable crops species from areas of Turkey where beet western yellows virus (BWYV), genus Polerovirus, family Luteoviridae was previously detected in pepper were surveyed for poleroviruses. Leaf samples were tested by DAS-ELISA, RT-PCR with degenerate primers for poleroviruses, and sequencing. Blast analysis of sequenced PCR amplicons revealed the presence of BWYV in broad bean (Vicia faba) and squash (Cucurbita pepo). These are new records of this virus on these two species in Turkey. [ABSTRACT FROM AUTHOR]

Five Potato leafroll virus (PLRV) isolates were collected from five states representing different potato growing parts of India. The ssRNA genome sequences of these isolates were determined. The genome comprised of 5,883 nucleotides and deduced genome organization resembled other PLRV isolates. About 97.6-98.7 % similarities was observed within the Indian isolates and were more close to European, Canadian, African, American and Czech isolates (95.8-98.6 %) than to an Australian isolate (92.9-93.4 %). These isolates were 43.7-53.1 % similar to other poleroviruses and 29.1-29.3 % to Barley yellow dwarf virus, a luteovirus. Out of five isolates, the isolate PBI-6 was recombinant one as detected by RDP3 software. Multiple sequence alignment of nucleotide and amino acid sequences of different ORFs indicated that the ORF 3 and ORF 4, corresponding to coat protein and movement proteins are more conserved than other ORFs. Amino acid changes specific to Indian isolates were observed and it was more in ORF 2 than in ORF 0, ORF 3 and ORF 4. This is the first report of complete genome sequence of PLRV isolates from India, which reveals low level genetic diversity. [ABSTRACT FROM AUTHOR]

Open-field pepper crops were sampled in 2011 in Turkey and Tunisia and surveyed for the major pepper-infecting viruses. As expected, potato virus Y and cucumber mosaic virus (in both countries), and tobacco etch virus (in Turkey only) were quite frequent. However, poleroviruses were the most common viruses, with prevalences above 70 %. Partial sequence analyses revealed the occurrence of poleroviruses resembling either beet western yellows virus (BWYV) or pepper vein yellows virus in the sampled areas, with BWYV being predominant in Turkey but in the minority in Tunisia. Poleroviruses should therefore be taken into account in disease control of pepper crops in the Mediterranean area. [ABSTRACT FROM AUTHOR]

The plant protein ARGONAUTE1 (AGO1) functions in multiple RNA-silencing pathways, including those of microRNAs, key regulators of growth and development. Genetic analysis of ago1 mutants with informative defects has provided valuable insights into AGO1's biological functions. Tomato encodes two AGO1 homologs (SlAGO1s), but mutants have not been described to date. To analyze SlAGO1s' involvement in development, we confirmed that both undergo decay in the presence of the Polerovirus silencing suppressor P0 and produce a transgenic responder line ( OP:P0HA) that, upon transactivation, expresses P0 C-terminally fused to a hemagglutinin (HA) tag (P0HA) and destabilizes SlAGO1s at the site of expression. By crossing OP:P0HA with a battery of driver lines, constitutive as well as organ- and stage-specific SlAGO1 downregulation was induced in the F1 progeny. Activated plants exhibited various developmental phenotypes that partially overlapped with those of Arabidopsis ago1 mutants. Plants that constitutively expressed P0HA had reduced SlAGO1 levels and increased accumulation of miRNA targets, indicating compromised SlAGO1-mediated silencing. Consistent with this, they exhibited pleiotropic morphological defects and their growth was arrested post-germination. Transactivation of P0HA in young leaf and floral organ primordia dramatically modified corresponding organ morphology, including the radialization of leaflets, petals and anthers, suggesting that SlAGO1s' activities are required for normal lateral organ development and polarity. Overall, our results suggest that the OP:P0HA responder line can serve as a valuable tool to suppress SlAGO1 silencing pathways in tomato. The suppression of additional SlAGOs by P0HA and its contribution to the observed phenotypes awaits investigation. [ABSTRACT FROM AUTHOR]

Potato leafroll virus (PLRV) is a destructive virus of potatoes and responsible for high yield losses wherever potatoes are grown. In this study, DNA fragments containing ORF0 from each of nine PLRV isolates was sequenced. Sequence analysis data using 36 isolates from 12 different countries including 14 Iranian isolates showed that the identities of ORF0 at both nucleotide and amino acid levels between the Iranian isolates were 96-100 % and these isolates were more similar to the European PLRV isolates than to the other isolates. Furthermore, phylogenetic and population genetic analysis were carried out on the basis of full-length ORF0 and overlapping and non-overlapping regions of ORF0 and ORF1 (ORF0/1) which revealed that PLRV isolates were not geographically resolved. Also, we identified negative selection with different ratios for each of the mentioned genomic regions suggesting effects of F-box motif and -1 frameshift on ORF0 non-overlapping region and ORF0/1 in the selection pressure, respectively. Five recombination events were detected in the Iranian, Australian, and European isolates suggesting an important role for this phenomenon in influencing genetic diversity within this virus population. [ABSTRACT FROM AUTHOR]

The worldwide distribution of Sugarcane yellow leaf virus (SCYLV) has led several research groups to study the function of the viral genome, the role of open reading frames (ORFs), their influence on virus accumulation and methods for diagnosis. The detection of SCYLV is usually based on the viral coat protein whether using serological and/or molecular techniques. In this study, ORF0 has been used as a diagnostic segment for SCYLV due to its highly conserved region in all SCYLV isolates. The results revealed that, ORF0 was expressed more consistently in all cultivars. In contrast, the expression of the coat protein varied. The RNA poleroviruses sequences of ORF0 were variable compared with the same segment of SCYLV populations. Analysis of the amino acid sequence of the ORF0 translation product revealed the presence of a potential transmembrane domain. The relatively high content of hydrophobic amino acids in the ORF0 protein further suggests that it may serve as a membrane anchor for the replication complex. [ABSTRACT FROM AUTHOR]

Tasmanian vegetable crops (broccoli, carrots, cauliflower, common bean, and pea) were tested for virus infection with Potyviruses (all crops), members of the Luteoviridae (all except carrot), Alfalfa mosaic virus (all except brassicas), Cucumber mosaic virus (all except carrot and cauliflower), Subterranean clover stunt virus (legumes only), Tomato spotted wilt virus (legumes only) and Cauliflower mosaic virus (brassicas only) over three seasons (2007-2010). Low (and sporadic) incidence of each virus (or virus group) was found in pea crops. Only Luteovirid and SCSV infections were found in bean crops at low frequency and incidence. Virus infection was not detected in carrot crops. Broccoli crops recorded generally low incidence of all four viruses or groups tested for, whilst cabbage crops recorded very low incidence of CaMV only. In the pea and broccoli crops members of the Luteoviridae were the most prevalent viruses detected. Samples that tested positive for generic Potyvirus and Luteoviridae tests were retested using virus specific antiserum and/or RT-PCR. Potyvirus detections (from pea crops in the first year of testing) were due to infection with Pea seed-borne mosaic virus (PSbMV). These samples were all sourced from a single imported seed line. Subsequent testing over the next two seasons failed to show evidence of PSbMV which may have been eliminated with destruction of the seed source. Molecular analyses of a selection of Luteovirid isolates revealed most infections were due to Turnip yellows virus with five isolates from pea belonging to a putative novel Polerovirus species with closest homology to Cucurbit aphid-borne yellows virus. [ABSTRACT FROM AUTHOR]

During 2010, yellowing symptoms were frequently observed in cultivated squash fields in Egypt. A total of 717 symptomatic squash leaf samples were collected from four regions where squash cultivation is of economic importance for the country: Kafrelsheikh, El-Behira, El-Sharkia and El-Ismailia. Serological analysis showed that 95.6% of the symptomatic squash samples were infected by Cucurbit aphid-borne yellows virus (CABYV), and visual estimation of the incidence of yellowing symptoms suggested a very high incidence of CABYV in the fields. Twelve CABYV isolates were characterized by sequencing two regions of the viral genome, open reading frame (ORF) 3 and ORFs 4/5. Overall, Egyptian isolates were very similar among them, and had higher similarity values with a French than with a Chinese isolate. The average nucleotide diversity for ORF 3 was significantly higher than for the other two regions, indicating that variability is not evenly distributed along the viral genome. The ratios between nucleotide diversity values in non-synonymous ( d) and synonymous ( d) positions ( d/ d) for each ORF showed that the three ORFs are evolving under different pressures, although predominantly under purifying selection. Phylogenetic analyses revealed that these Egyptian isolates, with only one exception, shared the same clade with a French isolate. Moreover, these analyses suggested that Egyptian isolates belong to the Mediterranean group described previously. [ABSTRACT FROM AUTHOR]

Plant viruses and aphids can interact via contest competition for plant resources and induce changes in plant physiology, which can have effects on a third trophic level. The aim of this study was to determine how the interactions between a circulative plant virus and its aphid vector may affect the performance of an endoparasitoid and how parasitism may affect the efficiency of virus transmission by its aphid vector. The timing when parasitized aphids were transferred to virus-infected lettuce leaves was critical for the performance of A. ervi. Higher parasitoid larvae mortality, longer developmental times and lower percentages of mummification were detected on viruliferous/parasitized aphid nymphs when the time lag between parasitism and exposure to the virus was less than 24 h. No significant differences were detected in virus transmission rate between parasitized and non-parasitized M. euphorbiae aphids. [ABSTRACT FROM AUTHOR]

Tobacco bushy top disease is caused by tobacco bushy top virus (TBTV, a member of the genus Umbravirus) which is dependent on tobacco vein-distorting virus (TVDV) to act as a helper virus encapsidating TBTV and enabling its transmission by aphids. Isometric virions from diseased tobacco plants were purified and disease symptoms were reproduced after experimental aphid transmission. The complete genome of TVDV was determined from cloned RT-PCR products derived from viral RNA. It was 5,920 nucleotides (nts) long and had the six major open reading frames (ORFs) typical of a member of the genus Polerovirus. Sequence comparisons showed that it differed significantly from any of the other species in the genus and this was confirmed by phylogenetic analyses of the RdRp and coat protein. SDS-PAGE analysis of purified virions gave two protein bands of about 26 and 59 kDa both of which reacted strongly in Western blots with antiserum produced to prokaryotically expressed TVDV CP showing that the two forms of the TVDV CP were the only protein components of the capsid. [ABSTRACT FROM AUTHOR]

The 5803 nt genomic sequence of a Sugarcane yellow leaf virus (SCYLV) isolate (SCYLV-chn1) from China was determined. It covered more than 98% of the complete viral genome and contained all the six ORFs and the entire intergenic untranslated region. This isolate was most closely related to SCYLV genotype CUB (isolates CUB-YL1 and CB86010) with identities of 95.2–97.4% (nt) (93.2–97.2% aa) in ORF0, ORF1, and ORF2. Sequence comparison and phylogenetic analyses supported the view that this isolate represents a new genotype; SCYLV CHN1 was suggested as the name for this new genotype. [ABSTRACT FROM AUTHOR]

Highlights from the article: To identify the pathogen, total RNA of 13 symptomatic samples from different tomato plants was extracted, and RT-PCR was carried out using the general polerovirus primers Pol-G-F and Pol-G-R (Knierim et al. [1]), whereas samples from asymptomatic tomato plants were used as negative controls. Tomato, Beet western yellows virus, Polerovirus.