Potato Leafroll Virus Research Articles

Commodity risk assessment of Petunia spp. and Calibrachoa spp. unrooted cuttings from Kenya.

The European Commission requested the EFSA Panel on Plant Health to evaluate the probability of entry of pests (likelihood of pest freedom at entry), including both regulated and non-regulated pests, associated with unrooted cuttings of the genera Petunia and Calibrachoa produced under physical isolation in Kenya. The relevance of any pest for this opinion was based on evidence following defined criteria, based on the methodology used for High-Risk Plants adapted for the specificity of this assessment. Fourteen EU-regulated pests (Bemisia tabaci, cowpea mild mottle virus, Liriomyza huidobrensis, Liriomyza sativae, Liriomyza trifolii, potato leafroll virus, potato spindle tuber viroid, Ralstonia pseudosolanacearum, R. solanacearum, Scirtothrips dorsalis, tomato mild mottle virus, tomato spotted wilt virus, tomato yellow leaf curl virus and Xanthomonas vesicatoria) and six EU non-regulated pests (Aleurodicus dispersus, pepper veinal mottle virus, Nipaecoccus viridis, Phenacoccus solenopsis, Tetranychus neocaledonicus and tomato yellow ring virus) fulfilled all relevant criteria and were selected for further evaluation. For these pests, the risk mitigation measures proposed in the technical dossier from Kenya were evaluated, taking into account the possible limiting factors. Additionally, an expert judgement is given on the likelihood of pest freedom, taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The estimated degree of pest freedom varies among the pests evaluated, with T. neocaledonicus being the pest most frequently expected on the imported cuttings. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9942 and 10,000 bags containing unrooted cuttings of Petunia spp. and Calibrachoa spp. per 10,000 would be free of T. neocaledonicus.

Complete genome characterization of cacao leafroll virus, a newly described cacao-infecting polerovirus.

The complete genome sequence of cacao leafroll virus (CaLRV; family Solemoviridae, genus Polerovirus) was determined by high-throughput sequencing of total RNA isolated from symptomatic cacao Theobroma cacao L. plants (n = 4). The CaLRV genome sequences ranged from 5,976 to 5,997 nucleotides (nt) in length and contained seven open reading frames (ORFs). Nucleotide and amino acid (aa) sequence comparisons showed that, among selected well-characterized poleroviruses, the CaLRV genome shared the highest nt sequence identity of 62% with that of potato leafroll virus (PLRV, NC_076505). A comparison of the predicted aa sequence of the CaLRV coat protein indicated that cotton leafroll dwarf virus (CLRDV, NC_014545) and melon aphid-borne yellows virus (MABYV, NC_010809) were the closest relatives, sharing 57% aa sequence identity. Bayesian phylogenetic analysis based on complete genome sequences showed that CaLRV grouped with well-characterized poleroviruses that cause diseases of cereal and vegetable crops. During the course of publishing this work, the nearly complete genome sequence of a member of the same polerovirus species, referred to as "cacao polerovirus" (OR605721), with which CaLRV shares 99% nt sequence identity, was reported.

Landscape‐scale patterns and predictors of potato viruses in Scotland

AbstractVirus diseases represent important economic threats to seed potato production worldwide, yet relatively little is known of their epidemiology at the landscape‐scale. In this study, data was compiled from the Scottish national seed potato classification scheme on the incidence of 10 different potato viruses for the years 2009–2022. A co‐occurrence analysis identified that 12 virus species pairs occurred together more often than expected by chance, and potato blackleg was positively associated with eight potato viruses. ArcGIS was used to investigate spatial and spatiotemporal variation in incidence rates of the three most prevalent viruses (potato virus Y, potato leaf roll virus and potato virus A), and this revealed prominent geographic differences in long‐term disease outcomes. Focusing on potato virus Y as the most commonly occurring single infection, interpretable machine‐learning techniques were used to investigate the influence of key crop, management and environmental factors on patterns of incidence in space and time. The results showed that health characteristics of seed stocks were among the most important predictors of incidence, along with blackleg infection, several management features, cultivar resistance, distance to the nearest seed and ware crop, temperature variables and several soil features. This approach provides a comprehensive overview of potato viruses in Scotland, a deeper understanding of epidemiological risk factors at the landscape‐scale and a forecast model that could serve as the basis of a decision support tool for improved management of potato virus Y.

Effects of meteorological variables on potato leaf roll virus and potato virus y infections on different potato varieties under natural and mulched conditions

After rice and wheat, potatoes are the third most important staple crop in Pakistan, but due to various virus diseases attacks, yield remains very low. Among viral pathogens, potato leaf roll virus (PLRV) and potato virus Y (PVY) are the most destructive viruses present in all potato-growing areas. A field experiment was conducted at the Research Farm of Plant Virology Section, Ayub Agricultural Research Institute, Faisalabad, to evaluate the effects of meteorological variables on the development of virus infections (PLRV and PVY) on different potato varieties under natural and mulched conditions. Results indicated that the development of infections of PVY and PLRV was delayed in different potato varieties under mulched conditions. The potato variety Simply Red had the highest PLRV and PVY disease incidences under unmulched and mulched circumstances, while Sahiwal Red and Ruby had the lowest infection rates. The least PVY disease incidence was noted under mulched conditions on FD-81-1. Mulched conditions were better in the reduction of diseases than unmulched conditions. The average high temperature (HT) ranged from 21.9 ◦C to 27 ◦C was most favorable for the development of PLRV and PVY on all six tested potato varieties in both conditions. The average low temperature (LT) ranged from 8 ◦C to 15 ◦C was favorable for the progression of PLRV and PVY diseases in both conditions. The relative humidity (RH) range of 50-60% was conducive for the development of PLRV and PVY diseases. It is concluded that mulching application is an essential tool to enhance the yield of potato crops by reducing their specific diseases.

Results of testing potato varieties in the European North

Relevance. Potato varieties Eurasia and Onezhskiy were developed as a result of cooperation between the Murmansk State Agricultural Experiment Station – branch of the VIR and the Leningrad Scientific Research Institute of Agriculture "Belogorka" and were included in the State Register of the Russian Federation in 2014 (Onezhsky) and in 2017 (Eurasia). To determine the prospects for cultivation in the Kola North, the varieties were tested in the conditions of the Murmansk region.Materials and methods. The research was carried out on the experimental field of the Murmansk State Agricultural Experiment Station – branch of the VIR in 2018-2020. Potato varieties Eurasia and Onezhskiy were obtained from the Leningrad Research Institute of Agriculture "Belogorka". The plot in the experiment included 4 rows of 15 tubers in each row. The planting pattern is 70x35 cm. Repetition – four times. The location of the plots is systematic with the plots being shifted along tiers. Early maturity was assessed using one test coping on the 70th day after planting. The Elizabeth variety was used as a standard. The results were processed using the method of analysis of variance according to Dospekhov.Results. The research results showed that the Onezhsky variety is distinguished by high starchiness, non-darkening flesh and good taste, is resistant to pathogens: Synchytrium endobioticum (Schilbersky) Percival, Streptomyces scabies (Thaxter), Globodera rostochiensis (Wollenweber) Behrens, relatively resistant to Phytophthora infestans (Mont . De Bary), is weakly affected by Potato virus Y (PVY), Potato leaf roll virus (PLRV). The Onezhsky variety, on average, over three years of research exceeded the standard sample in terms of yield and plant productivity. The Eurasia variety has high starchy content, good taste, culinary type B, is resistant to pathogens: Potato virus Y (PVY), Potato leaf roll virus (PLRV), Globodera rostochiensis (Wollenweber) Behrens, Synchytrium endobioticum (Schilbersky) Percival, moderately susceptible to Phytophthora infestans (Mont. De Bary). The Eurasia variety also exceeded the standard sample in terms of yield and plant productivity. Thus, the Onezhsky and Eurasia potato varieties are recommended for cultivation in the Kola North.

Differential occurrence and strain composition of potato viruses between two major seed potato production zones in China suggest the need for different management strategies for the zones

Viral disease is one of the major reasons leading to yield and quality reduction of potato production. To gain better knowledge about seed potato quality in China, the occurrences of six common viruses, including potato leafroll virus (PLRV) and potato viruses A (PVA), M (PVM), S (PVS), X (PVX) and Y (PVY), were investigated in two of China’s four potato production zones (specifically, Zone I and Zone IV) from 2013 to 2016. A total of 1231 random tuber samples (Zone I, n = 571; Zone IV, n = 660) and 532 symptomatic leaf samples (Zone I, n = 375; Zone IV, n = 157) were collected in seed potato and commercial potato fields and tested for the viruses by reverse transcription (RT)-PCR (tuber samples) and/or enzyme-linked immunosorbent assay (ELISA; leaf samples). The results showed that virus-free tubers accounted for 79.7% and 52.0% in seed tuber samples from zones I and IV, respectively. All of the six viruses analysed were present in both zones I and IV, but occurred at different frequencies, with PVY and PVS being the predominant viruses in zones I and IV, respectively. Moreover, 44.0% and 39.8% of the virus-positive samples in zones I and IV, respectively, were found to be infected with more than one virus. Strain typing of PVS and PVY demonstrated the existence of similar strains of PVY (i.e. PVYO, PVYNTNb, PVYN:O, PVYN- Wi, PVY – (SYR-I and -II) and of PVS (i.e. PVSO and PVSA) in both zones. For PVY, recombinant strains were predominant, with SYR-II (27.7%) being the most abundant strain in Zone I and SYR-I (53.3%) being the predominant strain in Zone IV. PVSO was the predominant strain in Zone I whereas PVSA was the dominant strain in Zone IV. This study revealed not only the high incidence of viruses in both seed and commercial potatoes in China, but also the differential occurrence and strain composition of the viruses between two major production zones in China for the first time. In addition, the study suggests the need for different management strategies for different production zones to enhance the quality of seed potatoes in China.

Virome Analysis of Aconitum carmichaelii Reveals Infection by Eleven Viruses, including Two Potentially New Species

Aconitum carmichaelii is a herbaceous herb indigenous to China that has been cultivated for traditional medicine for centuries. Virus-like symptoms of A. carmichaelii plants were observed on leaves in some A. carmichaelii plantations in Zhanyi and Wuding Counties, Yunnan Province, southwest China. High-throughput sequencing (HTS) was performed on 28 symptomatic plants, and the results revealed infection with 11 viruses, including 2 novel viruses and 9 previously described viruses: Aconitum amalgavirus 1 (AcoAV-1), aconite virus A (AcVA), cucumber mosaic virus (CMV), currant latent virus (CuLV), apple stem grooving virus (ASGV), chilli veinal mottle virus (ChiVMV), tomato spotted wilt orthotospovirus (TSWV), tobacco vein distorting virus (TVDV), and potato leafroll virus (PLRV). Two novel viruses tentatively named Aconitum potyvirus 1 and Aconitum betapartitivirus 1, were supported by sequence and phylogenetic analysis results of their genomes. We proposed the names Potyvirus aconiti and Betapartitivirus aconiti. RT-PCR assays of 142 plants revealed the predominance and widespread distribution of CMV, AcVA, and AcoPV-1 in plantations. The detection of isolates of CuLV, ASGV, ChiVMV, TSWV, TVDV, and PLRV infections for the first time in A. carmichaelii expands their known host ranges.

Exploring virus presence in field-collected potato leaf samples using RNA sequencing

BackgroundThe quick and accurate identification of viruses is essential for plant disease management. Next-generation sequencing (NGS) technology may allow the discovery, detection, and identification of plant pathogens. This study adopted RNA-sequencing (RNA-Seq) technology to explore the viruses in three potato plants (S3, S4, and S6) growing under field conditions. ResultsPotato-known infecting viruses, such as alfalfa mosaic virus (AMV), potato leafroll virus (PLRV), and potato virus Y (PVY), were identified using bioinformatics programs and validated using RT-PCR. The presence of these potato viruses was also confirmed by visual inspection of host symptoms. In addition, the nearly complete genome of PLRV and the complete or partial genome sequence of multipartite virus segments have been identified. Besides the three major potato viruses that BLASTn analysis revealed were present in our samples, BLASTx analysis revealed some reads are derived from other potato viruses, such as potato virus V (PVV), Andean potato latent virus (APLV), and tomato chlorosis virus (ToCV), which are not frequently reported in potato field screenings in Egypt. Other microbial agents, such as bacteria and fungi, were also identified in the examined sample sequences. Some mycovirus sequences derived from ourmia-like viruses and Alternaria alternata chrysovirus were also identified in sample S4, confirming the complexity of the potato microbiome under field conditions. ConclusionNGS quickly and accurately identifies potato plant viruses under field conditions. Implementing this technology on a larger scale is recommended to explore potato fields and imported plants, where symptoms may be absent, unspecific, or only triggered under certain conditions.

Potato Viruses of Economic Importance for Production of Planting Material in Bulgaria

Potato is the world’s third most widespread food crop, following wheat and rice. Tubers play an important role in the spread of virus diseases in different regions in Bulgaria for seed production. The most important viruses in potatoes in Bulgaria include Potato virus Y (PVY), Potato leaf roll virus (PLRV), Potato virus S (PVS), and Potato virus M (PVM). Most of the viruses in potatoes do not induce symptoms in tubers, which plays an important role in viral dissemination by the growers. In this way, after planting the tubers, the quality and yield of the production may be severely reduced. The use of virus-free tubers by growers is of key importance for the control of diseases and the reduction of loss of production.

Afidopyropen as a potential tool for Potato leafroll virus management in post-neonicotinoid potato production.

Potato leafroll virus (PLRV) has been well managed by neonicotinoids since their widespread adoption in the United States, becoming virtually absent from seed and production fields in the Northwest. However, with increasing interest in discontinuing neonicotinoid usage, there is concern that PLRV could enjoy a resurgence in the absence of effective alternative chemistries. We tested the effects of afidopyropen, an insecticide with novel mode of action, on PLRV transmission and the feeding/probing behavior of its primary vector, the green peach aphid (Myzus persicae [Sulzer]). Afidopyropen foliar sprays decreased PLRV transmission by individual green peach aphids relative to water controls: PLRV acquisition from treated potato plants and subsequent transmission was reduced by 89%, and PLRV inoculation by viruliferous aphids to treated potato plants was reduced by 35%. Although electropenetrograph analyses following 4-h recordings of individual aphids on potato plants showed decreases in the total and mean duration of phloem feeding (E) on plants subject to an afidopyropen treatment relative to water, these only trended toward significance. Taken together, these results suggest treatment with afidopyropen can decrease PLRV transmission in potatoes, but that significant changes in feeding/probing might not occur quickly post-exposure. Overall, while the reductions in transmission were not as dramatic as have been observed following neonicotinoid treatments, afidopyropen may be a useful alternative and should be evaluated in field experiments.

A Previously Undescribed Polerovirus (Solemoviridae) Infecting Theobroma cacao Germplasm.

Cacao Theobroma cacao L. (Malvaceae) is an economically important crop cultivated in tropical climates for the bean from which chocolate and other products are made (Zarrillo et al., 2018). Virus-like symptoms consisting of discoloration, leaf distortion with downward rolling of leaves, and yellow speckling or mottling (Fig. S1), were observed in imported cacao germplasm at the USDA-ARS-SHRS cacao quarantine facilities in the fall of 2020. Total RNA was isolated from leaves collected from four symptomatic plants using silica RNA extraction method (Rott and Jelkmann, 2001). Ribosomal RNA (rRNA)-depleted RNA samples were used for cDNA library construction, followed by high throughput sequencing on Illumina® NovaSeq 6000 platform (Novogene Corp., Sacramento, CA). Quality-filtered, 150-bp paired-ended reads (2,601,293-3,104,474) were assembled de novo using SPAdes v.3.14.1 (Nurk et al., 2013). The contigs (200,799 to 276,851) were queried against the NCBI virus reference sequence (RefSeq) database using the discontiguous megablast algorithm (https://blast.ncbi.nlm.nih.gov/Blast.cgi?). The resultant contigs (n=1,344) were 150-nt to 1463-nt in length (k-mer coverage from 6.3x to 26,721.7x) and shared their highest nucleotide (nt) identity with potato leafroll virus (PLRV; NC_001747; genus Polerovirus; family Solemoviridae), at 69.1%-72.8%. The contigs pooled from the four samples were assembled into 15 scaffolds. BLASTn analyses of the 15 scaffolds against the RefSeq database indicated the best matches were to thirteen other polerovirus species, with top hits to cereal yellow dwarf virus-RPV (D10206) and pepper vein yellows virus (LC528383), having similarity scores of 66.2% and 100% respectively. The 15 scaffolds matched to the 5' terminal end, ORF1-2, ORF3, ORF4 and ORF3-5 of the different polerovirus genomes. For confirmatory sequencing, total RNA was subjected to reverse transcription using SuperScript IV (Invitrogen, Carlsbad, CA), followed by RT-PCR amplification with general polerovirus primers PoconF/PoconcpR (Xiang et al., 2008) expected to yield an amplicon of ~1,400-bp located at the 3' end of the RNA-dependent, RNA polymerase (RdRp), including the complete coat protein (CP) and movement protein (MP) genes. Amplicons were ligated to pGEM-T Easy vector (Promega, Madison, WI) and sequenced bi-directionally by Sanger sequencing (Eton Bio, Research Triangle Park, NC). BLASTn analysis of the polerovirus-like nt sequences (GenBank accession nos. (ON745771-ON745774) indicated the closest relatives were potato leafroll virus (OK058524) and cucumber aphid-borne yellows virus (FJ460218), at 71% and 73%, respectively. The CP amino acid (aa) sequence shared the greatest similarity to cereal yellow dwarf virus RPV (NP_840023), at 53%, and the MP aa sequence shared the greatest aa similarity to wheat yellow leaf dwarf virus-GPV (YP_003029842), at 38%. These results provide robust support for the association of a previously undescribed polerovirus with symptomatic cacao trees, herein named, cacao leafroll virus (Solemoviridae; Polerovirus). Although Koch's postulates have not been completed to confirm causality, the presence of this virus in cacao germplasm undermine efforts to distribute pathogen-free germplasm and may pose a risk to cacao production in trees established from virus-infected plant material. To our knowledge, this is the first report of a polerovirus infecting cacao trees. All trees of these accessions at the quarantined facility in Miami, FL have been destroyed.

Molecular Determination of Some Important Viruses Causing Infection in Potato Fields in Turkey

Potato is one of the most important agricultural crops worldwide and known to be susceptible to more than 40 viruses in nature. In this research, 298 leaf samples collected from potato fields in Afyon, Nevşehir and Bolu provinces in the previous study were used to determine viruses affecting potato production in the region. The leaves of potato plants showing virus symptoms were subjected to RT-PCR using virus-specific primers, in order to detect the presence of Potato leafroll virus (PLRV), Potato virus A (PVA), Potato virus X (PVX) and Potato virus M (PVM). As a result of the study,one or more viruses were detected in 46 (15.43%) of the 298 leaf samples tested. A total of 43 samples infected with PLRV (14.42%) and 3 sample infected with PVX (1.%). It was determined that the most common virus in plant samples collected from Afyon, Nevşehir and Bolu Central regions was PLRV followed by PVX. PVA and PVM were not detected in the samples. The sequences of some positive isolates of PLRV were obtained and used along with the isolates registered in the GenBank to reveal phylogenetic relationships among them. PLRV isolates from Turkey were classified in Group 2 along with isolates from Serbia, Canada, and Pakistan based on phylogenetic analyses.

A new simple and effective method for PLRV infection to screen for virus resistance in potato

Effective screening of plant germplasm collections for resistance to plant viruses requires that there is a rapid and efficient system in place to challenge individual plants with the virus. Potato leafroll virus (PLRV), a commercially important pathogen of potato, is able naturally to infect only the phloem-associated tissue of plants and is delivered to this tissue by feeding aphids. Mechanical (non-vector-mediated) infection by PLRV does not occur thus screening for PLRV resistance is currently laborious and time consuming. We constructed an infectious cDNA clone of a new (Hutton) isolate of PLRV in the binary vector pDIVA and transformed it into Agrobacterium tumefaciens strain LBA4404. Infiltration of this culture into leaves of Nicotiana benthamiana, a highly susceptible model plant, produced a systemic infection with PLRV, although this approach was not successful for potato. However, a very efficient and reproducible systemic infection of potato was achieved when we submerged cut stems of the plant into the agrobacterium cell suspension and then transplanted the stems into compost to grow roots and new apical leaves. Using a standardised protocol developed for this new PLRV inoculation method we have confirmed the previously described resistance to the virus in the JHI breeding line G8107(1) and identified 62 plant accessions from the Commonwealth Potato Collection in which no PLRV infection was detected.

Development of Reverse Transcription Recombinase Polymerase Amplification (RT-RPA): A Methodology for Quick Diagnosis of Potato Leafroll Viral Disease in Potato.

Potatoes are developed vegetatively from tubers, and therefore potato virus transmission is always a possibility. The potato leafroll virus (PLRV) is a highly devastating virus of the genus Polerovirus and family Luteoviridae and is regarded as the second-most destructive virus after Potato virus Y. Multiple species of aphids are responsible for the persistent and non-propagating transmission of PLRV. Due to intrinsic tuber damage (net necrosis), the yield and quality are drastically diminished. PLRV is mostly found in phloem cells and in extremely low amounts. Therefore, we have attempted to detect PLRV in both potato tuber and leaves using a highly sensitive, reliable and cheap method of one-step reverse transcription-recombinase polymerase amplification (RT-RPA). In this study, an isothermal amplification and detection approach was used for efficient results. Out of the three tested primer sets, one efficiently amplified a 153-bp product based on the coat protein gene. In the present study, there was no cross-reactivity with other potato viruses and the optimal amplification reaction time was thirty minutes. The products of RT-RPA were amplified at a temperature between 38 and 42 °C using a simple heating block/water bath. The present developed protocol of one-step RT-RPA was reported to be highly sensitive for both leaves and tuber tissues equally in comparison to the conventional reverse transcription-polymerase chain reaction (RT-PCR) method. By using template RNA extracted employing a cellular disc paper-based extraction procedure, the method was not only simplified but it detected the virus as effectively as purified total RNA. The simplified one-step RT-RPA test was proven to be successful by detecting PLRV in 129 samples of various potato cultivars (each consisting of leaves and tubers). According to our knowledge, this is the first report of a one-step RT-RPA performed using simple RNA extracted from cellular disc paper that is equally sensitive and specific for detecting PLRV in potatoes. In terms of versatility, durability and the freedom of a highly purified RNA template, the one-step RT-RPA assay exceeds the RT-PCR assay, making it an effective alternative for the certification of planting materials, breeding for virus resistance and disease monitoring.

Effectiveness of Botanical Pesticides from Wastes of Virginia Tobacco Stems in Reducing Populations of Leaf-Sucking Pest and Occurrence of Virus Disease Symptoms on Potato Plants

The potato plant (Solanum tuberosum L.) is a tuber-producing plant which is rich in carbohydrates, protein and minerals, and can be used as a staple food, and potatoes have great potential as one of the horticultural crops that can support world food diversification. One of the constraining factors in increasing potato productivity is leaf-sucking pests including aphids (Aphids spp.,), whitefly (Bemisia tabaci), and thrips (Thrips Palmi Karny), which besides damaging plants directly, can act as vectors for viruses that cause potato plant diseases such as Potato virus Y (PVY) and Potato leaf roll virus (PLRV). These two viruses can cause quite severe damage and through the health of the seeds they produce, they can reduce potato productivity by up to 70-80%. This study aims to determine the effect of several concentrations of botanical pesticides from Virginia tobacco stem waste on the emergence of viral disease symptoms in potato plants. The experiment was carried out in Sembalun Bumbung Village, East Lombok Regency (Indonesia), which was arranged using a Randomized Block Design consisting of 6 treatments namely control, abamectin, and Virginia tobacco stem waste botanical pesticides with concentrations of 2, 4, 6 and 8 ml/L. The results showed that the botanical pesticides from Virginia tobacco stem waste were effective in reducing leaf-sucking pest populations and suppressing the intensity of leaf-sucking pest attacks and were able to suppress the emergence of viral disease symptoms, with a concentration of 8 ml/L botanical pesticides more effective than other treatments in controlling populations. and attacks by potato leaf-sucking pests suspected as virus vectors.

Potato viruses in Kazakhstan and methods for obtaining virus-free seed material

Potato (Solanum tuberosum L.) is a staple food worldwide, including in Kazakhstan. The potato yield in 2021 in the country was only 20 tonnes per ha, which is a rather low indicator. One of the main reasons for the insufficient yield of potatoes in Kazakhstan is the low quality of seed material, and the main requirement for high-quality seed material is the absence of viral diseases. Viral diseases in crops are a major impediment to sustainable potato production, as they cause large losses in crop quantity and quality. To date, 40 viral potato diseases have been discovered worldwide. Depending on the infection of viral diseases, the yield can be reduced by up to 90% in crop production. In this review, we discuss in detail the current state of potato viral diseases in Kazakhstan and characterise the most common potato viruses in the country, including potato virus M (PVM), potato virus (PVS), potato virus X (PVX), potato virus Y (PVY) and potato leafroll virus (PLRV). To ensure food security of the country and prevent the spread of infection with viral diseases, popular methods (ELISA, RT-PCR and detection of specific types of targets using microarrays) for the early detection of potato plant viruses in seed and field material are considered. For the mass production of virus-free potato plant material, the use of temporary immersion bioreactors is discussed, as well as the use of modern genetic engineering methods to obtain plant varieties resistant to the most common viral diseases.

Viromes of Field-Grown Tomatoes and Peppers in Tennessee Revealed by RNA Sequencing Followed by Bioinformatic Analysis

The prevalent viruses in a population of 106 tomato and 53 pepper field-grown plants in Tennessee was investigated by RNA sequencing and analysis as two separate pools of ribosomal-depleted total RNA. Contigs of potato leafroll virus (PLRV), red clover vein mosaic virus, tomato spotted wilt virus, and a novel rhabdovirus were detected only in tomato and those of bell pepper endornavirus (BPEV) and pepper cryptic virus 2 (PCV-2) only in pepper. Additionally, contigs of five other viruses (solanum nigrum ilarvirus 1, SNIV-1; southern tomato virus, STV; tobacco vein-clearing virus, ToVCV; tomato mosaic virus, ToMV; and tomato ringspot virus, ToRSV) were detected in both tomatoes and peppers. Moreover, contigs were assembled of a potentially novel tobamovirus from both tomatoes and peppers. The presence of PLRV, STV, ToVCV, and the novel tobamovirus sequences in the original tomato samples and those of BPEV, PCV-2, ToMV, and ToRSV in the original pepper samples were confirmed by RT-PCR followed by Sanger sequencing. This study represents the first survey of viromes of field-grown tomatoes and peppers in Tennessee. To the best of our knowledge, SNIV-1, STV, and ToVCV have not been reported previously to be associated with peppers elsewhere in the world.

Prevalence and molecular characterization of important potato viruses in the Tokat province of Turkey.

It is believed that viruses affect potato yield more than any other pathogens worldwide. We report here on a survey of the four most common potato viruses in the Tokat Province of northern Turkey. Leaf samples were collected from potato plants showing signs of viral diseases in five districts of the province. Over 400 leaf samples were tested using RT-PCR with virus-specific primers. Among the one or more viruses detected in 218 (52%) leaf samples, Potato virus Y (PVY) was the most common (47.1%), followed by potato virus S (PVS; 16.7%), potato virus X (PVX; 6.0%) and potato leaf roll virus (PLRV; 5.3%). The most common mixed infections were PVY + PVS (6.9%). A phylogenetic analysis of the gene sequences showed all Turkish PVS isolates to be clustered with the PVSO group, two PVY isolates with the PVYN-WI group and one isolate with the PVYNTN group. Turkish PVX isolates are in the Type X group of the two major PVX isolate groups. The Turkish PLRV isolates were separated into two major groups depending on the results of the phylogenetic analysis, with six cases in Group 1 and one in Group 2. PVY, PVX, PVS and PLRV were detected in potato production areas in Tokat. A phylogenetic comparison of the gene sequences revealed all Turkish isolates to be immigrant members of the world populations of these viruses. Our results emphasize the importance of the strict quarantine control of plant materials entering Turkey.

Systematic mutagenesis of Polerovirus protein P0 reveals distinct and overlapping amino acid functions in Nicotiana glutinosa

The protein P0 serves as the viral suppressor of RNA silencing (VSR) for poleroviruses, but elicits the hypersensitive response (HR) in specific Nicotiana species. We subjected P0 proteins from turnip yellows virus (P0Tu) and potato leafroll virus (P0PL) to serial deletion and performed extensive site-directed mutagenesis of P0Tu. Most deletions of the N-terminus and many substitution mutations disrupted both HR elicitation and VSR activity. Two conserved blocks of amino acid residues were found to be associated with HR. A double lysine to arginine substitution in HR-specific block 1 caused P0Tu to elicit a more robust HR. Conversely, deletion or mutation of block 2 in the C-terminus preserved VSR activity, but impaired HR elicitation, allowing virus escape from Nicotiana glutinosa resistance when expressed in the heterologous potato virus X vector. Our observations suggest that P0 residues responsible for suppressing RNA silencing and eliciting HR have overlapping, but distinct functions.

Polerovirus N-terminal readthrough domain structures reveal molecular strategies for mitigating virus transmission by aphids

Poleroviruses, enamoviruses, and luteoviruses are icosahedral, positive sense RNA viruses that cause economically important diseases in food and fiber crops. They are transmitted by phloem-feeding aphids in a circulative manner that involves the movement across and within insect tissues. The N-terminal portion of the viral readthrough domain (NRTD) has been implicated as a key determinant of aphid transmission in each of these genera. Here, we report crystal structures of the NRTDs from the poleroviruses turnip yellow virus (TuYV) and potato leafroll virus (PLRV) at 1.53-Å and 2.22-Å resolution, respectively. These adopt a two-domain arrangement with a unique interdigitated topology and form highly conserved dimers that are stabilized by a C-terminal peptide that is critical for proper folding. We demonstrate that the PLRV NRTD can act as an inhibitor of virus transmission and identify NRTD mutant variants that are lethal to aphids. Sequence conservation argues that enamovirus and luteovirus NRTDs will follow the same structural blueprint, which affords a biological approach to block the spread of these agricultural pathogens in a generalizable manner.