Leafroll Virus Research Articles

Diagnóstico serológico y molecular del Potato leafroll virus (PLRV) en tubérculos-semilla de papa en Antioquia, Colombia

<p>Las virosis son uno de los problemas fitosanitarios más limitantes para la producción de papa, siendo los virus Potato leafroll virus (PLRV), Potato virus Y (PVY), Potato virus S (PVS) y Potato ye-llow vein virus (PYVV) los que generan mayores pérdidas económicas en la región andina. Gene-ralmente estos virus son transmitidos por insectos hemípteros y por tubérculos-semilla. En esta investigación se evaluó la presencia y distribución del PLRV en tubérculos de <em>Solanum tuberosum</em> variedad Diacol-Capiro y S. phureja variedad Criolla-Colombia obtenidos en Antioquia, utilizando pruebas serológicas y moleculares. Mediante DAS-ELISA se evaluaron 128 muestras consisten-tes en tres tipos de tejidos (piel, yemas latentes y brotes), mientras que con RT-PCR en tiempo real (RT-qPCR), se utilizó un subgrupo de 12 muestras de cada variedad. Utilizando DAS-ELISA, el PLRV se encontró en el 3,1% y 10,1% de las muestras de Diacol-Capiro y Criolla-Colombia, respectivamente; siendo evidente una mayor detección del virus en la piel de los tubérculos de ésta última variedad. Las pruebas de RT-qPCR detectaron el PLRV en 83,3% y 91,6% de las 12 muestras de Diacol-Capiro y de Criolla-Colombia, respectivamente; con valores de Ciclo umbral (CT) entre 17,72 y 30,59. La naturaleza de los amplicones obtenidos por RT-qPCR fue confirmada por secuenciación como parte de una región codificante de la cápside del PLRV (Identidad=99%-100%). Estos resultados enfatizan en la necesidad de utilizar tubérculo-semilla certificados por su sanidad viral en los cultivos de papa del país y de fortalecer dichos programas a partir del empleo de técnicas de detección altamente sensibles como RT-qPCR.</p>

Visualization of Host-Polerovirus Interaction Topologies Using Protein Interaction Reporter Technology.

Demonstrating direct interactions between host and virus proteins during infection is a major goal and challenge for the field of virology. Most protein interactions are not binary or easily amenable to structural determination. Using infectious preparations of a polerovirus (Potato leafroll virus [PLRV]) and protein interaction reporter (PIR), a revolutionary technology that couples a mass spectrometric-cleavable chemical cross-linker with high-resolution mass spectrometry, we provide the first report of a host-pathogen protein interaction network that includes data-derived, topological features for every cross-linked site that was identified. We show that PLRV virions have hot spots of protein interaction and multifunctional surface topologies, revealing how these plant viruses maximize their use of binding interfaces. Modeling data, guided by cross-linking constraints, suggest asymmetric packing of the major capsid protein in the virion, which supports previous epitope mapping studies. Protein interaction topologies are conserved with other species in the Luteoviridae and with unrelated viruses in the Herpesviridae and Adenoviridae. Functional analysis of three PLRV-interacting host proteins in planta using a reverse-genetics approach revealed a complex, molecular tug-of-war between host and virus. Structural mimicry and diversifying selection-hallmarks of host-pathogen interactions-were identified within host and viral binding interfaces predicted by our models. These results illuminate the functional diversity of the PLRV-host protein interaction network and demonstrate the usefulness of PIR technology for precision mapping of functional host-pathogen protein interaction topologies. The exterior shape of a plant virus and its interacting host and insect vector proteins determine whether a virus will be transmitted by an insect or infect a specific host. Gaining this information is difficult and requires years of experimentation. We used protein interaction reporter (PIR) technology to illustrate how viruses exploit host proteins during plant infection. PIR technology enabled our team to precisely describe the sites of functional virus-virus, virus-host, and host-host protein interactions using a mass spectrometry analysis that takes just a few hours. Applications of PIR technology in host-pathogen interactions will enable researchers studying recalcitrant pathogens, such as animal pathogens where host proteins are incorporated directly into the infectious agents, to investigate how proteins interact during infection and transmission as well as develop new tools for interdiction and therapy.

Effect of antiviral chemicals on in vitro regeneration response and production of PLRV-free plants of potato

Potato leaf roll virus (PLRV) is causing serious loss in yield and quality of potatoes. In the present study, the effect of seven antiviral chemicals viz. Acyclovir, 5-Azacytidine, Cytarabine, 5-Bromouracil, Ribavirin, 2-Thiouracil and Zidovudine on regeneration response and production of PLRV-free plants under in vitro conditions is reported. MS medium supplemented with 0.1 mg L−1 GA3, 0.1 mg L−1 NAA and 500 mg L−1 malt extract was used for regeneration of plantlets from nodal explants. DAS-ELISA and RT-PCR was used for virus indexing of the mother plant and in vitro-regenerated plantlets. Explants of PLRV positive potato plants were cultured on this medium containing different concentrations (5 – 30 mg L−1) of antiviral chemicals. Shoot regeneration response varied between tested antiviral chemicals and was decreased with increase in concentration of antiviral chemicals from 5 to 30 mg L−1. Antiviral chemicals at 30 mg L−1 concentration showed strong inhibitory effect on regeneration response of shoots. In vitro regenerated plantlets tested negative in both ELISA and RT-PCR were only considered as virus free. When regeneration response and number of virus-free plants produced was compared, 2- thiouracil and ribavirin (25 mg L−1) were found to be effective. 2- thiouracil (25 mg L−1) gave 38.68% PLRV free plants with 30.55% cultures showing shoot regeneration and ribavirin (25 mg L−1) gave 39.62% PLRV-free plants with 36.80% cultures showing shoot regeneration. Regeneration response of explants was better on 5-Bromouracil at 30 mg L−1 concentrations but it was found least effective in production of PLRV-free potato plants.

Molecular diversity of turncurtoviruses in Iran.

Turnip curly top virus (TCTV) is the only member of the newly established genus Turncurtovirus (family Geminiviridae). As part of an ongoing study to identify additional plant hosts and the diversity of turncurtoviruses, between 2012 and 2014, we sampled symptomatic turnip plants and other crops in the provinces Fars and Khorasan Razavi (southern and northeastern Iran, respectively). Infection by turncurtoviruses was tested by PCR and/or rolling-circle amplification (RCA) coupled with restriction enzyme digests. Turncurtoviruses were identified in turnip as well as seven other field crops, including eggplant, basil, radish, lettuce, sugar beet, red beet and spinach. Full turncurtovirus genomes were recovered from 25 of these samples, leading to the identification of TCTV and a new putative turncurtovirus, turnip leaf roll virus (TLRV; 13 isolates), which shares <80% genome-wide pairwise identity with TCTV. Agroinoculation of plants with an infectious clone of TLRV demonstrated that this virus could infect several plant hosts under greenhouse conditions and could be transmitted by the leafhopper Circulifer haematoceps (Mulsant and Rey, 1855) from agroinoculated to healthy plants.

Detection of arabis mosaic virus and grapevine leafroll virus I during the period of vegetation

A b s t r a c t : In 1987, at 13 different dates leaf samples from vines infected with AMY and GLRYI were collected from different positions in the plants. All results showed that the Tris extraction buffer system produced better results than the Nicotin buffer system. Before flowering AMY could be detected in young leaves better than in elder ones with all buffer systems, whereas after flowering the results changed and it was possible to detect AMY only with the Tris system in elder leaves. For GLR VI only the T ris buffer system was us.ed. GLRYI could only be detected from the end of August to the end of the vegetation period. Samples from elder leaves produced higher extinction than those from younger ones for GLRYI. A correlation between the results in ELISA test and the tempe~arures before the sampling dates could nor be proved.

Development and Reproduction of Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) Fed on Myzus persicae (Sulzer) (Hemiptera: Aphididae) Vectoring Potato leafroll virus (PLRV).

The aim of this study was to evaluate the biological parameters of Chrysoperla externa (Hagen) while feeding on Myzus persicae (Sulzer) acting as a vector of potato leafroll virus (PLRV). In laboratory experiments, three different diets were offered ad libitum to C. externa during the larval period: M. persicae fed on PLRV-infected potato leaves, M. persicae fed on uninfected potato leaves, and eggs of the factitious prey Anagasta kuehniella (Zeller) as the control. The following parameters were studied: the developmental time and survival rate of the larval and pupal stages, the sex ratio, the proportion of fertile females, female fecundity and egg viability, and the survival curve of the first 30 days after adult emergence. PLRV-infected aphids influenced the C. externa larval developmental time and survival compared to PLRV-uninfected aphids and A. kuehniella eggs. The pupal developmental time of C. externa was shorter when fed on aphids compared to A. kuehniella eggs, but no differences were recorded between the PLRV-infected and uninfected aphid diets. Additionally, no differences were observed for pupal survival and reproduction. However, adult survival was affected by the prey type, as 75% of C. externa control adults remained alive at an age of 30 days compared to 51 and 54% for those fed on PLRV-uninfected and infected aphids, respectively.

First report of Chickpea chlorotic dwarf virus naturally infecting chickpea in Tunisia

Chickpea ( Cicer arietinum ) is one of three important legume species grown in Tunisia. Five viral species are known to infect chickpea in Tunisia: Bean leaf roll virus , Beet mosaic virus , Beet western yellows virus , Chickpea chlorotic stunt …

Potato leafroll virus structural proteins manipulate overlapping, yet distinct protein interaction networks during infection.

Potato leafroll virus (PLRV) produces a readthrough protein (RTP) via translational readthrough of the coat protein amber stop codon. The RTP functions as a structural component of the virion and as a nonincorporated protein in concert with numerous insect and plant proteins to regulate virus movement/transmission and tissue tropism. Affinity purification coupled to quantitative MS was used to generate protein interaction networks for a PLRV mutant that is unable to produce the read through domain (RTD) and compared to the known wild-type PLRV protein interaction network. By quantifying differences in the protein interaction networks, we identified four distinct classes of PLRV-plant interactions: those plant and nonstructural viral proteins interacting with assembled coat protein (category I); plant proteins in complex with both coat protein and RTD (category II); plant proteins in complex with the RTD (category III); and plant proteins that had higher affinity for virions lacking the RTD (category IV). Proteins identified as interacting with the RTD are potential candidates for regulating viral processes that are mediated by the RTP such as phloem retention and systemic movement and can potentially be useful targets for the development of strategies to prevent infection and/or viral transmission of Luteoviridae species that infect important crop species.

Insights into the polerovirus-plant interactome revealed by coimmunoprecipitation and mass spectrometry.

Identification of host proteins interacting with the aphidborne Potato leafroll virus (PLRV) from the genus Polerovirus, family Luteoviridae, is a critical step toward understanding how PLRV and related viruses infect plants. However, the tight spatial distribution of PLRV to phloem tissues poses challenges. A polyclonal antibody raised against purified PLRV virions was used to coimmunoprecipitate virus-host protein complexes from Nicotiana benthamiana tissue inoculated with an infectious PLRV cDNA clone using Agrobacterium tumefaciens. A. tumefaciens-mediated delivery of PLRV enabled infection and production of assembled, insect-transmissible virus in most leaf cells, overcoming the dynamic range constraint posed by a systemically infected host. Isolated protein complexes were characterized using high-resolution mass spectrometry and consisted of host proteins interacting directly or indirectly with virions, as well as the nonincorporated readthrough protein (RTP) and three phosphorylated positional isomers of the RTP. A bioinformatics analysis using ClueGO and STRING showed that plant proteins in the PLRV protein interaction network regulate key biochemical processes, including carbon fixation, amino acid biosynthesis, ion transport, protein folding, and trafficking.

Agronomic characterization variety Quebranta in the Ica region, Peru

The study was to identify the best strains of the Quebranta variety cultivated in Peruvian region of Ica during campaigns 2011 to 2014. The evaluations were conducted in fourteen vineyards and the criteria to evaluate each one of them was that the same owner vineyard, would identify the best strain Quebranta for their good performance and sanitary quality. Productive parameters as grape weight and number of bunches per vine, average cluster weight, length and width of cluster and Berry weight were evaluated. Within the parameters of vegetative growth was assessed Ravaz index and as parameter for the composition of the grape was evaluated the concentration soluble solids (°Brix), total acidity and pH. Four phenological stages were recorded and defined from observed events in the branch of the year: Phase I comprising bud of winter to sprouting; Phase II of sprouting to full bloom; Phase III of full bloom to veraison and Phase IV of veraison to maturity. At the time of fruit setting were taken leaf samples to assess the State of health of each strain to Grapevine fanleaf virus, Grapevine fleck virus, Grapevine leafroll virus 1, Grapevine leafroll virus 3 and Tomato ringspot virus. The variables average bunch weight (22%), berry weight (20%), bunch length (13%) and bunch width (11%) presented the lowest values coefficient of variation. The variables of weight of grape per vine (52%), number of bunch (42%) and index of Ravaz (60%) has the highest values of coefficient of variation. Four variables were used that showed lower values (25%) coefficient of variation for the weighted average. The variables that presented perfect correlation were berry weight and width of bunch, berry weight and Ravaz index, length of bunch and Ravaz index. The analysis of conglomerate allowed to group the strains in study in two groups which showed a significant difference between them (p < 0.0001). The principal component analysis identified that the variable of weight per bunch, index Ravaz and berry weight distinguished the 77 strains studied. Soluble solids, acidity and pH of the grapes from the fourteen vineyards present significant difference. The phenology of the 77 study strains does not present significant difference. Samples of tender leaves were used for virus scanning. Only the variables of length and width of bunch showed a coefficient of variation acceptable accuracy. The weighted average analysis allowed choosing the best strains which are: QT1; QT5; QCH2; QCH3; QYJ1; QT2; QT3; QYJ4; QT4; QCH1 which will serve as base material for future certifications and improvement of this variety. The variables such as the number of bunch and bunch width feature the highest perfect correlation (0.89%). The grape presented in average 24.67 °Brix, acidity 4.14 g/L tartaric acid and 3.92 of pH. The phenological period total average of the 77 strains was 202 days and shows no significant difference. The results of the analysis of virus were negative for the 77 strains and for the five viruses that were analyzed.

First Report of Potato mop top virus Causing Potato Tuber Necrosis in Colorado and New Mexico.

Potato mop top virus (PMTV) is considered the type member of the genus Pomovirus. PMTV is an important pathogen of potato vectored by the plasmodiophorid Spongospora subterranea f. sp. subterranea (Sss), which causes powdery scab of potato (1). Sss and PMTV are usually associated with cool and humid environments. PMTV-infected potato tubers generally exhibit internal hollow necrotic spots or concentric rings, and the virus is known to cause significant economic losses in Northern Europe, North and South America, and Asia (4). PMTV in the United States was first reported in Maine (2). Potato (Solanum tuberosum L.) tubers cv. FL2048 and cv. Atlantic were sent to our laboratory from fields in Saguache County in Colorado and in San Juan County in New Mexico, respectively, during the spring of 2013. The tubers from both locations had multiple, internal, concentric, necrotic arcs and circles. Internal tissue with necrotic lesion from six symptomatic tubers from each location were crushed in liquid nitrogen followed by ribonucleic acid extraction using a Total RNA Isolation kit (Promega Corp., Madison, WI). These extracts were tested by reverse transcription (RT)-PCR using three different sets of previously published primers for molecular detection of PMTV. The primer set H360/C819 targeting the coat protein (CP) on RNA 3 of PMTV yielded an amplicon (H360-CO and H360-NM) of 460 bp (4). The second set of primers, pmtF4/pmtR4 (5), amplified a 417-bp product (PMTF-CO and PMTF-NM) in RNA 2, and the third set, PMTV-P9/PMTV-M9 (3), designed to amplify the region encoding an 8-KD cysteine-rich protein in RNA 3 of PMTV, yielded a 507-bp amplicon (PMTV9-CO and PMTV9-NM). The amplicons generated from RT-PCR using all three sets were cloned (PGEMT-easy) and sequenced. Since the sequences from symptomatic tuber extracts from each location were identical to their respective primer sets, a consensus sequence from each primer set was submitted to National Center for Biotechnology Information (NCBI) GenBank. Sequences obtained from the H360/C819 primer set (GenBank Accession Nos. KM207013 and KM207014 for H360-CO and H360-NM, respectively) were 100% identical to the corresponding CP regions of PMTV isolates from North Dakota (HM776172). Sequences from the pmtF4/pmtR4 primer set (KM207015 and KM207016 for PMTF-CO and PMTF-NM, respectively) were 100% identical to the corresponding protein in RNA2 of PMTV isolates from North Dakota (GenBank HM776171), and sequences from the PMTV-P9/PMTV-M9 primer set (KM207017 and KM207018 for PMTV9-CO and PMTV9-NM respectively) were 99% identical to the corresponding protein in RNA3 of PMTV isolates (AY187010). The 100-99% homology of the sequences from this study to the corresponding PMTV sequences published in NCBI confirmed the occurrence of symptoms in the tubers from both Colorado and New Mexico due to PMTV. None of the symptomatic tubers tested positive for Tobacco rattle virus, Tomato spotted wilt virus, Alfalfa mosaic virus, Potato leafroll virus, or the necrotic strains of Potato virus Y by RT-PCR. To our knowledge, this is the first report of PMTV in potato in states of Colorado and New Mexico.

Eliminating Potato Virus Y (PVY) and Potato Leaf Roll Virus (PLRV) Using Cryotherapy of in vitro-grown Potato Shoot Tips

Potato virus Y (PVY) and potato leafroll virus (PLRV) are among the most damaging potato viruses and prevalent in most potato growing areas. In this study, cryopreservation was used to eradicate PVY and PLRV using two cryogenic methods. Potato shoot tips proliferated in vitro were cryopreserved through droplet-vitrification and encapsulation-vitrification using plant vitrification solution 2 (PVS2; 30% glycerol + 15% dimethyl sulfoxide + 15.0% ethylene glycol + 13.7% sucrose) and modified PVS2. Both cryogenic procedures produced similar rates of survival and regrowth, which were lower than those from shoot tip culture alone. The health status of plantlets regenerated from shoot tip culture alone and cryopreservation was checked by reverse transcription-polymerase chain reaction. The frequency of virus-free plants regenerated directly from highly proliferating shoot tips reached 42.3% and 48.6% for PVY and PLRV, respectively. In comparison, the frequency of PVY and PLRV eradication after cryopreservation was 91.3~99.7% following shoot-tip culture. The highest cryopreserved shoot tip regeneration rate was observed when shoot tips were 1.0~1.5 mm in length, but virus eradication rates were very similar (96.4~99.7%), regardless of shoot tip size. This efficient cryotherapy protocol developed to eliminate viruses can also be used to prepare potato material for safe long-term preservation and the production of virus-free plants.

Detection of Multiple Potato Viruses in the Field Suggests Synergistic Interactions among Potato Viruses in Pakistan.

Viral diseases have been a major limiting factor threating sustainable potato (Solanum tuberosum L.) production in Pakistan. Surveys were conducted to serologically quantify the incidence of RNA viruses infecting potato; Potato virus X (PVX), Potato virus Y (PVY), Potato virus S (PVS), Potato virus A (PVA), Potato virus M (PVM) and Potato leaf roll virus (PLRV) in two major potato cultivars (Desiree and Cardinal). The results suggest the prevalence of multiple viruses in all surveyed areas with PVY, PVS and PVX dominantly widespread with infection levels of up to 50% in some regions. Co-infections were detected with the highest incidence (15.5%) for PVX and PVS. Additionally the data showed a positive correlation between co-infecting viruses with significant increase in absorbance value (virus titre) for at least one of the virus in an infected plant and suggested a synergistic interaction. To test this hypothesis, glasshouse grown potato plants were challenged with multiple viruses and analyzed for systemic infections and symptomology studies. The results obtained conclude that multiple viral infections dramatically increase disease epidemics as compared to single infection and an effective resistance strategy in targeting multiple RNA viruses is required to save potato crop.

IMPROVED DETECTION OF ILARVIRUSES AND NEPOVIRUSES AFFECTING FRUIT TREES USING QUANTITATIVE RT-qPCR

Reverse transcription quantitative PCR (RT-qPCR) assays were developed for the detection of the ilarviruses Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV), Apple mosaic virus (ApMV), and American plum line pattern virus (APLPV), and the nepoviruses Tomato ringspot virus (ToRSV) and Cherry leafroll virus (CLRV). These viruses affect various stone fruits such as apricots, cherries, peaches, plums, and almonds. The goal of this work was to improve the RT-qPCR detection of PNRSV, PDV, and ApMV in addition to developing three new RT-qPCR assays for the detection of APLPV, ToRSV and CLRV. Primers for conventional RT-PCR as well as primers and probes for RT-qPCR assays were designed after aligning coat protein (CP) gene sequences of geographically diverse isolates with the corresponding CP gene sequences from GenBank, targeting regions with 100% sequence identity. The efficiency of each RT-qPCR assay, as well as the intra- and inter-assay variability, were determined. These conventional RT-PCR and RT-qPCR assays were validated using purified total RNAs from 221 trees from the USDA Clonal Germplasm Repository orchards. The data showed that more isolates were detected by RT-qPCR than by RT-PCR.

First Report of Potato leaf roll virus (PLRV) Naturally Occurring on Jute (Corchorus olitorius) in India.

Jute (Corchorus olitorius L.) is an important bast fiber crop that is mainly grown in the Southeast Asian countries like India, Bangladesh, Nepal, China, Indonesia, Thailand, Myanmar, and a few South American countries. In June 2013, symptoms suggestive of a viral disease were noticed on jute (cv. JRO524) in an experimental field of the CRIJAF research farm, Barrackpore, India, and the incidence of the disease was less than 2%. The infected plants showed stunted growth and short height. Mostly the upper leaves elongated with curling and coiling of lamina. Puckering and shoe string effect were also noticed. Petioles and stipules of the affected leaves were exceptionally longer. Although initially the incidence was low, it may spread to larger areas in subsequent years. Because the jute fiber is extracted from the stem, stunted growth and short height would badly affect the fiber yield and quality. Ten symptomatic and ten asymptomatic healthy looking samples were collected from the field. Corchorus golden mosaic begomovirus is common in jute; therefore, all the samples were tested by PCR using JMFL-AF/JMFL-AR, DNA-A component specific primer pair and JMFL-BF/JMFL-BR, DNA-B component specific primer pairs (1). However, there was no amplification. Because the aphid Aphis gossypii was often noticed in the jute field, all the samples were tested by double-antibody sandwich (DAS)-ELISA for common aphid transmitted viruses, e.g., Cucumber mosaic virus, Bean common mosaic virus, Cowpea mosaic virus, Papaya ring spot virus, Potato leaf roll virus (PLRV), Potato virus Y, and Watermelon mosaic virus using commercial diagnostic kits (Agdia). The symptomatic samples showed positive reaction only for PLRV. Five ELISA-positive samples and five asymptomatic healthy samples were used for RNA extraction. Total RNA was extracted by using QIAGEN RNeasy mini kit. RT-PCR was carried out with PLRV CP gene specific primer pair (3) which generated a cDNA amplicon of 627 bp in all ELISA-positive symptomatic samples. PLRV was not detected in symptomless samples. The five purified cDNA products were cloned in a pGEM-T Easy vector (Promega) and were sequenced. One of the five identical sequences was deposited in GenBank (Accession No. KF233880). The consensus sequence was analyzed by NCBI BLAST and found to share 99% similarity with the coat protein sequence of PLRV reference strain (S77421). Nucleotide span and ORF finder (NCBI) analysis indicated the 627-bp PCR amplicon coded part of a coat protein gene that had 100% identity with translated gene product (Protein ID AAB33483). PLRV is a small isometric RNA virus with worldwide distribution belonging to the family Luteoviridae whose natural host range is mainly restricted to solanaceous plants and few plants of other families (2,4). To the best of our knowledge, this is the first report of PLRV naturally occurring on jute (C. olitorius).

Aphid behavioral responses to virus‐infected plants are similar despite divergent fitness effects

AbstractWe compared the settling preferences and reproductive potential of an oligophagous herbivore, the pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae), in response to pea plants, Pisum sativum L. cv. ‘Aragorn’ (Fabaceae), infected with two persistently transmitted viruses, Pea enation mosaic virus (PEMV) and Bean leaf roll virus (BLRV), that differ in their distribution within an infected plant. Aphids preferentially oriented toward and settled on plants infected with PEMV or BLRV in comparison with sham‐inoculated plants (plants exposed to herbivory by uninfected aphids), but aphids did not discriminate between plants infected with the two viruses. Analysis of plant volatiles indicated that plants inoculated with either virus had significantly higher green leaf volatile‐to‐monoterpene ratios. Time until reproductive maturity was marginally influenced by plant infection status, with a trend toward earlier nymph production on infected plants. There were consistent age‐specific effects of plant infection status on aphid fecundity: reproduction was significantly enhanced for aphids on BLRV‐infected plants across most time intervals, though mean aphid fecundity did not differ between sham and PEMV‐infected plants. There was no clear pattern of age‐specific survivorship; however, mean aphid lifespan was reduced on plants infected with PEMV. Our results are consistent with predictions of the host manipulation hypothesis, extended to include plant viruses: non‐viruliferous A. pisum preferentially orient to virus‐infected host plants, potentially facilitating pathogen transmission. These studies extend the scope of the host manipulation hypothesis by demonstrating that divergent fitness effects on vectors arise relative to the mode of virus transmission.

Elicitation of hypersensitive responses in Nicotiana glutinosa by the suppressor of RNA silencing protein P0 from poleroviruses.

Plant disease resistance (R) proteins that confer resistance to viruses recognize viral gene products with diverse functions, including viral suppressors of RNA silencing (VSRs). The P0 protein from poleroviruses is a VSR that targets the ARGONAUTE1 (AGO1) protein for degradation, thereby disrupting RNA silencing and antiviral defences. Here, we report resistance against poleroviruses in Nicotiana glutinosa directed against Turnip yellows virus (TuYV) and Potato leafroll virus (PLRV). The P0 proteins from TuYV (P0(T) (u) ), PLRV (P0(PL) ) and Cucurbit aphid-borne yellows virus (P0(CA) ) were found to elicit a hypersensitive response (HR) in N. glutinosa accession TW59, whereas other accessions recognized P0(PL) only. Genetic analysis showed that recognition of P0(T) (u) by a resistance gene designated RPO1 (Resistance to POleroviruses 1) is inherited as a dominant allele. Expression of P0 from a Potato virus X (PVX) expression vector transferred recognition to the recombinant virus on plants expressing RPO1, supporting P0 as the unique Polerovirus factor eliciting resistance. The induction of HR required a functional P0 protein, as P0(T) (u) mutants with substitutions in the F-box motif that abolished VSR activity were unable to elicit HR. We surmised that the broad P0 recognition seen in TW59 and the requirement for the F-box protein motif could indicate detection of P0-induced AGO1 degradation and disruption of RNA silencing; however, other viral silencing suppressors, including the PVX P25 that also causes AGO1 degradation, failed to elicit HR in N. glutinosa. Investigation of P0 elicitation of RPO1 could provide insight into P0 activities within the cell that trigger resistance.

Walnut (Juglans).

Walnut species are important nut and timber producers in temperate regions of Europe, Asia, South America, and North America. Trees can be impacted by Phytophthora, crown gall, nematodes, Armillaria, and cherry leaf roll virus; nuts can be severely damaged by codling moth, husk fly, and Xanthomonas blight. The long generation time of walnuts and an absence of identified natural resistance for most of these problems suggest biotechnological approaches to crop improvement. Described here is a somatic embryo-based transformation protocol that has been used to successfully insert horticulturally useful traits into walnut. Selection is based on the combined use of the selectable neomycin phosphotransferase (nptII) gene and the scorable uidA gene. Transformed embryos can be germinated or micropropagated and rooted for plant production. The method described has been used to establish field trials of mature trees.

Indexing of Potato leaf roll virus (PLRV) from Potato Growing Areas of Punjab, India

Indexing of Potato leaf roll virus (PLRV) from Potato Growing Areas of Punjab, India

A novel combination of a new umbravirus, a new satellite RNA and potato leafroll virus causes tobacco bushy top disease in Ethiopia.

Etiological studies of a recently emerged bushy top disease of tobacco in Ethiopia indicated that a ~4.5-kb dsRNA from infected plants represents an umbravirus, whereas a smaller band (~0.5 kb) is that of a new satellite RNA. Potato leafroll virus was also consistently associated with the disease. The three agents, whose experimental host ranges are restricted to members of the family Solanaceae, always occurred together in field samples and are transmitted together by the aphid Myzus persicae nicotianae. The umbravirus, which represents a new species, is most closely related to groundnut rosette virus, and the name Ethiopian tobacco bushy top virus is proposed.