Potato Virus M Research Articles

Distribution and species composition of potato viruses in the Novosibirsk region.

Among the many diseases that affect potato plants, viral infections are the most common and cause significant damage to farms, affecting both the yield and quality of potatoes. In this regard, an important condition for preserving the potato seed fund in Russia is systematic monitoring and early highly specific detection of potato viral infections. The purpose of the work is to study samples of potato varieties collected in the Novosibirsk region for the presence of viral infections using RT-PCR. 130 potato plants from three districts of the Novosibirsk region (NR) were studied. As a result of monitoring, the following viruses were identified: PVY (potato virus Y), PVS (potato virus S), PVM (potato virus M) and PVX (potato virus X). The quarantine pathogen potato spindle tuber viroid (PSTVd) was not detected in any of the samples analyzed. The maximum frequency of occurrence in the region was noted for three viruses: PVY, PVM and PVS. A significant proportion of the samples were mixed viral infections: the occurrence of the combination of infection PVY + PVM in plants was 25.0 %, and PVY + PVS, 22.6 %. To develop methods for determining the strain affiliation of the studied samples, the nucleotide sequences of the capsid protein genes of 10 Y-virus isolates were sequenced. Phylogenetic analysis of the studied sequences of NR isolates was carried out with a set of sequences of reference strains 261-4, Eu-N, N:O, NE-11, NTNa, NTNb, N-Wi, O, O5, SYR_I, SYR_II and SYR_III retrieved from GenBank. As a result of phylogenetic analysis, it was established that NR viral samples fell into two groups of strains: group 1, which also includes isolates of the reference strains 261-4/SYR_III, and group 2, NTNa. The obtained results of the strain affiliation of NR samples lay the basis for the development of DNA and immunodiagnostic systems for identifying PVY circulating in NR, as well as for elucidating the source and routes of entry of specific virus strains.Key words: Solanum tuberosum; viral infections; RT-PCR; potato Y virus; phylogenetic analysis.

VIRAL DISEASES OF POTATOES IN KAZAKHSTAN

Potato (Solanum tuberosum L.) is a staple food crop worldwide, including Kazakhstan. Viral infections represent a major obstacle to sustainable potato production due to deterioration of both qualitative and quantitative indicators. To determine the current status of the main viral diseases Y, X, M, S, PLRV, plant and seed material (tubers) from different potato growing regions of Kazakhstan was sampled. Multiplex polymerase chain reaction by reverse transcription (mpRT-PCR) and primers specific for coat protein (CP) were used to amplify the corresponding viruses. Monitoring of seed material revealed that the most prevalent virus in almost all regions, was potato virus S (PVS). Analysis of plant material sampled in the fields revealed that the most common viruses in the regions were potato virus M (PVM) and potato virus S (PVS). The work done to monitor viral diseases in different regions of Kazakhstan will provide a basis for directing future efforts to control and monitor the phytosanitary status of potato in the country.

Genetic diversity of Potato virus M (PVM) in the major potato growing region in the Indo-Gangetic plain and characterization of a distinct strain of PVM occurring in India

Potato virus M (PVM) is one of the most prevalent viruses infecting potatoes worldwide, showing a wide range of diversity in their populations; however, the diversity and genome information of PVM occurring in India is hardly known. The present study serologically detected the PVM in 22.8% of leaf samples collected from the potato fields, generated 13 coat protein (CP) genes and one complete genome sequence for the isolates from India, and identified four differential hosts confirming PVM-Del-144 as a distinct strain of PVM occurring in India. The phylogenetic analyses conducted based on the CP gene sequences (14 from India and 176 from other countries) suggested the existence of three evolutionary divergent lineages (PVM-o, PVM-d, and a new divergent group) in the PVM population, where isolates from India belong to only two clusters (PVM-o and PVM-d) within four sub-clusters. High levels of nucleotide diversity (0.124) and genetic distance (0.142) recorded among the isolates from India may be due to the deviation from the neutral evolution and experiencing population expansion in the past. The complete genome of the isolate Del-144 (KJ194171; 8,526 nucleotides) shared 92.2–93.9% nt sequence identity with the population of PVM-o, whereas it shared only 70.2–72.1% identity with PVM-d. In the phylogenetic analyses, Del-144 clustered with the isolates of PVM-o; however, it formed a separate branch away from all other isolates, indicating the diversity of the strain. Overall, this study revealed the diversity of the isolates of PVM from India and reported the first complete genome sequence of a distinct strain of PVM occurring in India.

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.

Effect of infection of potato plants by Potato virus Y (PVY), Potato virus S (PVS), and Potato virus M (PVM) on content and physicochemical properties of tuber starch.

Potato virus Y (PVY), Potato virus S (PVS), and Potato virus M (PVM) infection of potato plants leads to decreased dry matter and starch content in tubers. Starch samples from potato tubers infected with PVY, PVS, and PVM had higher amylose content. Granules of starch isolated from potato tubers infected by PVS exhibit larger granules than starch granules isolated from tubers of healthy plants. In contrast, in the case of PVM and PVY infection, starch granules were significantly smaller in diameter. A decrease in the degree of crystallinity has been observed in all samples of starches obtained from the tubers of infected plants compared to starch isolated from tubers of healthy plants. A slight decrease in gelatinization temperature was noted for starch samples isolated from tubers infected by PVY and PVM, and a slight increase in gelatinization temperature for starch samples isolated from tubers infected by PVS compared to starch isolated from tubers of healthy plants. In all samples of starch obtained from tubers of infected plants, an increase in the value of gelatinization enthalpy was observed. Thus, it can be concluded that damage to potato plants by PVM and PVY leads to a significant decrease in the quality of starch in tubers. At the same time, infection by PVS had practically no considerable effect.

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.

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.

Partial Elimination of Viruses from Traditional Potato Cultivar ‘Brinjak’ by Chemotherapy and Its Impact on Physiology and Yield Components

Viruses are responsible for more than 50% of annual potato tuber yield losses and cause great economic damage. The traditional Croatian potato cultivar ‘Brinjak’ is important for local growers because of its economically profitable production and as a gene pool for future breeding programs. However, the full genetic potential of the cultivar cannot be exploited due to virus infection. In this study, we attempted to eliminate potato virus M (PVM) and potato virus S (PVS) from potato cultivar ‘Brinjak’ and to evaluate the effects on physiological parameters and yield. Shoot apices were isolated from PVM + PVS-infected sprouts and cultivated for six weeks on MS medium with the addition of 50 or 100 mg L−1 ribavirin. The surviving shoot apices were micropropagated. The in vitro post-eradication period lasted 200 days. DAS-ELISA and RT-PCR were performed on R0 and R1 plants 90 days after acclimatization to determine the sanitary status of the plants. Chlorophyll fluorescence and multispectral imaging were performed on the R0 plants at the same time. The success of PVS elimination was 33% at both ribavirin concentrations. However, neither concentration was successful in eliminating PVM. Plants with mixed infection (PVM + PVS) had more severe disease symptoms compared to PVM-infected plants, affecting photochemistry and multispectral parameters and, consequently, yield. PVM + PVS plants had significantly lower number and weight of tubers per plant and lower average tuber weight than plants with single PVM infection in most of the generations studied. The results indicate a strong negative impact of PVS in mixed infections with PVM and show the importance of its elimination from potato plants.

Eukaryotic translation initiation factor 4E family member nCBP facilitates the accumulation of TGB-encoding viruses by recognizing the viral coat protein in potato and tobacco.

Due to their limited coding capacity, plant viruses have to depend on various host factors for successful infection of the host. Loss of function of these host factors will result in recessively inherited resistance, and therefore, these host factors are also described as susceptibility genes or recessive resistance genes. Most of the identified recessive resistance genes are members of the eukaryotic translation initiation factors 4E family (eIF4E) and its isoforms. Recently, an eIF4E-type gene, novel cap-binding protein (nCBP), was reported to be associated with the infection of several viruses encoding triple gene block proteins (TGBps) in Arabidopsis. Here, we, for the first time, report that the knockdown of nCBP in potato (StnCBP) compromises the accumulation of potato virus S (PVS) but not that of potato virus M (PVM) and potato virus X (PVX), which are three potato viruses encoding TGBps. Further assays demonstrated that StnCBP interacts with the coat proteins (CPs) of PVS and PVM but not with that of PVX, and substitution of PVS CP in the PVS infectious clone by PVM CP recovered the virus infection in StnCBP-silenced transgenic plants, suggesting that the recognition of PVS CP is crucial for StnCBP-mediated recessive resistance to PVS. Moreover, the knockdown of nCBP in Nicotiana benthamiana (NbnCBP) by virus-induced gene silencing suppressed PVX accumulation but not PVM, while NbnCBP interacted with the CPs of both PVX and PVM. Our results indicate that the nCBP orthologues in potato and tobacco have conserved function as in Arabidopsis in terms of recessive resistance against TGB-encoding viruses, and the interaction between nCBP and the CP of TGB-encoding virus is necessary but not sufficient to determine the function of nCBP as a susceptibility gene.

Virus Elimination from Naturally Infected Field Cultivars of Potato (Solanum tuberosum) by Transgenic RNA Interference.

Tissue culture methods enable virus elimination from vegetatively propagated crop plants but cannot prevent new infections. Here we used a tissue culture transgenic approach for curing field cultivars of Solanum tuberosum through the stimulation of RNA interference (RNAi)-based antiviral defenses. Expression cassettes carrying inverted repeats of potato virus S (PVS, genus Carlavirus) movement or coat protein sequences were used for the transformation of potato cultivars naturally infected with PVS and/or a related carlavirus potato virus M (PVM), without or with potato virus Y (PVY, genus Potyvirus). A high proportion of transformants PCR-positive for transgenes were cured from both carlaviruses and PVY. After 3-year field trials, 22 transgenic lines representing seven cultivars remained free of any virus or became infected only with PVY. Vegetative progenies of the transgenic lines of cultivar Zeren (initially coinfected with PVS, PVM, and PVY), sampled after in vitro propagation or field trials, and other field cultivars accumulated transgene-derived 21, 22, and 24 nt small interfering (si)RNAs almost exclusively from the PVS inverted repeats. Additionally, some field progenies accumulated 21–22 nt siRNAs from the entire PVY genome, confirming PVY infection. Taken together, transgenic RNAi is effective for virus elimination from naturally infected potato cultivars and their sequence-specific immunization against new infections.

Eradication of Potato Virus S, Potato Virus A, and Potato Virus M From Infected in vitro-Grown Potato Shoots Using in vitro Therapies.

Certain viruses dramatically affect yield and quality of potatoes and have proved difficult to eradicate with current approaches. Here, we describe a reliable and efficient virus eradication method that is high throughput and more efficacious at producing virus-free potato plants than current reported methods. Thermotherapy, chemotherapy, and cryotherapy treatments were tested alone and in combination for ability to eradicate single and mixed Potato virus S (PVS), Potato virus A (PVA), and Potato virus M (PVM) infections from three potato cultivars. Chemotherapy treatments were undertaken on in vitro shoot segments for four weeks in culture medium supplemented with 100 mg L−1 ribavirin. Thermotherapy on in vitro shoot segments was applied for two weeks at 40°C (day) and 28°C (night) with a 16 h photoperiod. Plant vitrification solution 2 (PVS2) and cryotherapy treatments included a shoot tip preculture followed by exposure to PVS2 either without or with liquid nitrogen (LN, cryotherapy) treatment. The virus status of control and recovered plants following therapies was assessed in post-regeneration culture after 3 months and then retested in plants after they had been growing in a greenhouse for a further 3 months. Microtuber production was investigated using in vitro virus-free and virus-infected segments. We found that thermotherapy and cryotherapy (60 min PVS2 + LN) used alone were not effective in virus eradication, while chemotherapy was better but with variable efficacy (20–100%). The most effective result (70–100% virus eradication) was obtained by combining chemotherapy with cryotherapy, or by consecutive chemotherapy, combined chemotherapy and thermotherapy, then cryotherapy treatments irrespective of cultivar. Regrowth following the two best virus eradication treatments was similar ranging from 8.6 to 29% across the three cultivars. The importance of virus removal on yield was reflected in “Dunluce” free of PVS having higher numbers of microtubers and in “V500’ free of PVS and PVA having a greater proportion of microtubers > 5 mm. Our improved procedure has potential for producing virus-free planting material for the potato industry. It could also underpin the global exchange of virus-free germplasm for conservation and breeding programs.

Occurrence and distribution of viruses infecting potato in Russia.

Potato viral disease has been a major problem in potato production worldwide including Russia. Here, we detected Potato Virus M (PVM), P (PVP), S (PVS), Y (PVY), and X (PVX) and Potato Leaf Roll Virus (PLRV) by RT-PCR on potato leaves and tubers from the Northwestern (NW), Volga (VF), and Far Eastern (FE) federal districts of Russia. Each sample was co-infected with up to five viruses. RT-PCR disclosed all six viruses in NW, three in VF, and five in FE. Phylogenetic analyses of PVM and PVS strains resolved all PVM isolates in Group O (ordinary) and all PVS isolates in Group O. Seven PVY strains were detected, and they included only recombinants. PVY recombinants were thus the dominant potato virus strains in Russia, although they widely varied among the regions. Our research provides insights into the geographical distribution and genetic variability of potato viruses in Russia.

Dynamics of Flexible Viruses in Polymer Solutions

We examine the coupling of the dynamics of flexible viral nanoparticles to the dynamics of comparably sized polymer chains. Using fluorescence microscopy, we quantify the dynamics of three filamentous viruses, potato virus M (PVM), M13, and pf1, that are suspended in semidilute solutions of partially hydrolyzed polyacrylamide. The dynamics of the viral nanoparticles are approximately diffusive on accessible time and length scales, but the distributions of displacements are non-Gaussian and exhibit increasingly extended tails as the aspect ratio of the viruses or the polymer concentration is increased. The long-time diffusion coefficients do not collapse onto a universal curve based on existing models for rodlike or spherical nanoparticles that are comparably sized to the polymer chains. Instead, the diffusivities appear to collapse as a function of the ratio of the polymer correlation length and a length scale intermediate between the virus radius and length, indicating that the hydrodynamic coupling to the polymer dynamics is affected by the virus anisotropy and flexibility.

Identification, prevalence and genetic diversity study of potato viruses in Northeastern states of India

AbstractPotato affecting viruses is an important biotic factor that hampers both the quality and yield of potato production worldwide. The occurrence of potato viruses has been historically recorded in India. Viruses such as potato virus X (PVX), potato virus Y (PVY), potato virus A (PVA), potato virus M (PVM), potato virus S (PVS), potato leafroll virus (PLRV) have been recorded in all potato growing zones. To investigate the presence and distribution of potato virus diseases in North‐East India, a survey of seven major potato growing regions was conducted during the 2017 and 2018 growing seasons. The presence of potato viruses was confirmed by double antibody sandwich ELISA (DAS‐ELISA) with reverse transcriptase polymerase chain reaction (RT‐PCR) performed on selected samples. The sequencing followed by annotation of PCR amplicons obtained from RT‐PCR showed 95–100% nucleotide sequence identities with respective virus accessions on NCBI GenBank. The multiple sequence analysis and phylogenetic studies provided an overview of the genetic diversity pattern among different potato virus isolates. This study reveals a broad picture of the potato virus infections occurring in Northeastern states of India, which may be useful to develop effective control strategies against the potato viruses.

Prevalence, distribution and control of six major potato viruses in Kenya

In most developing countries, farmers lack sufficient supply of certified or healthy potato seed tubers. Hence, they often plant their own saved ware potato tubers, a practice that is known to contribute to spread and increase the prevalence of plant viruses. In this study, we proposed options for managing the virus based on the knowledge obtained from surveys of virus prevalence and distribution in potato cultivars grown under such conditions. Potato leaf samples randomly collected from 354 farms in five major potato-growing counties in Kenya were tested for six potato viruses; potato virus Y (PVY), potato leaf roll virus (PLRV), potato virus X (PVX), potato virus M (PVM), potato virus A (PVA) and potato virus S (PVS) through DAS-ELISA. Virus prevalence in the fields was high; 72.9% of the samples were positive for at least one of the six viruses; and 55.9% showed multiple infections. A follow-up survey conducted during three consecutive seasons, in two of the five counties, revealed that virus prevalence fluctuated across seasons. This suggested that updated information on virus prevalence might be of value for designing a virus control strategy. Distribution maps showed the presence of the viruses restricted to specific geographic regions, an indication of where control efforts should be directed. Four cultivars, Sherekea, Shangi, Kenya Karibu and Asante, grown at a high virus-prevalent area, showed low values of average ELISA absorbance (OD), suggest a field resistance to the viruses. This study demonstrated that knowledge of prevalence and distribution may be of value to identify and recommend virus resistant cultivars to replace susceptible ones, especially in the virus hotspot areas.

Molecular Detection of Potato Viruses in Bangladesh and Their Phylogenetic Analysis.

Potato (Solanum tuberosum) is a major food source in the whole world including Bangladesh. Viral diseases are the key constraint for sustainable potato production by reducing both quality and quantity. To determine the present status of eight important potato viruses in Bangladesh, tuber samples were collected from three major potato growing regions (Munshiganj, Jessore and Bogra districts) in January–February 2017 and February 2018. Reverse transcription polymerase chain reaction (RT-PCR) with coat protein (CP)-specific primers were used to amplify CP sequences of the respective viruses, and confirmed by sequencing, which were deposited in the GenBank. Results indicated that the tuber samples were subjected to Potato leafroll virus (PLRV), Potato virus X (PVX), Potato virus Y (PVY), Potato virus S (PVS), Potato virus H (PVH), Potato aucuba mosaic virus (PAMV) and Potato virus M (PVM) infection, whereas mixed infections were very common. Phylogenetic analysis revealed that the PLRV from this study was closely related to a Canadian and a Chinese isolate, respectively; PVX was closely related to a Canadian and a Chinese isolate, respectively; PVY was closely related to a Chinese isolate; PVS was closely related to a Chinese and an Iranian isolate, respectively; PAMV was closely related to a Canadian isolate; PVH was closely related to a Huhhot isolate of China; and PVM was closely related to an Indian and an Iranian isolate, respectively. As far as we know, PAMV in this study is the first report in Bangladesh. These findings will provide a great scope for appropriate virus control strategies to virus free potato production in Bangladesh.

Molecular detection and identification of eight potato viruses in Gansu province of China

Potato (Solanum tuberosum), a major food crop in the world is commonly infected with viral diseases, causing a loss in both quality and quantity of this crop. To determine the prevalence of eight important potato viruses in Gansu province of China, tuber samples were collected from Weiheyuan potato seed industry development Co., Ltd., and nineteen different commercial potato production fields at different locations in October 2018. Viruses were identified by RT-PCR using coat protein (CP)-specific primers, and validated by cloning three PCR positive amplicons of each virus followed by sequencing of three positive clones from each plasmid. Sequences were deposited in the GenBank. RT-PCR results demonstrated that mixed infections were very common in the collected tuber samples. Mixed infection of Potato virus X (PVX) and Potato virus S (PVS) caused 12.5 %; PVX and Potato aucuba mosaic virus (PAMV) caused 20.83 %; PVX, PVS and PAMV caused 12.5 %; PVX, Potato virus H (PVH) and PAMV caused 8.33 %; Potato leafroll virus (PLRV), PVX, PVS and PAMV caused 8.33 %; PVX, PVS, PVH and PAMV caused 16.67 %; PLRV, PVX, PVS, PVH and PAMV caused 8.33 %; and PVX, PVS, PVH, PAMV and Potato virus M (PVM) caused 4.17 % tuber infection, respectively; whereas, Potato virus Y (PVY) and Potato virus A (PVA) were not detected. PVY and PVA requires further testing in the future, and the result for these two viruses in the current study cannot be validated due to the lack of positive controls. PVS and PVH were also confirmed by western blot analysis. Phylogenetic analysis further revealed that the PLRV from Gansu was closely related to a Guangdong isolate (GenBank accession no. MF062487), PVX was closely related to a Shandong isolate (GenBank accession no. AF628555), PVS was closely related to a Guangxi isolate (GenBank accession no. KF011279) and an Australi isolate (GenBank accession no. GU319949), PVH was closely related to a Yunnan isolate (GenBank accession no. JQ904630), PAMV was closely related to a Bangladeshi isolate (GenBank accession no. MF133526), and PVM was closely related to a Tanzania isolate (GenBank accession no. KC866622). These findings will provide a basis for control of potato viruses in this region in the future.

Prevalence of R Genes for Resistance to Potato Viruses in Uganda Germplasm

The most important potato viruses in Uganda are Potato virus Y (PVY), Potato leafroll virus (PLRV), Potato virus X (PVX), Potato virus S (PVS), Potato virus A (PVA) and Potato virus M (PVM). Utilization of R genes in breeding for resistance to viruses has not been explored in Uganda due to limited information on the prevalence of R genes in the available genotypes. This study aimed at identifying potato genotypes with R genes for resistance to potato viruses important in Uganda. The study screened 71 potato accessions from the National Potato Breeding Programme at Kachwekano Zonal Agricultural Research and Development Institute for the presence of resistance genes to viruses using diagnostic molecular markers. The results indicated that 21 out of 71 genotypes had resistance markers, of which nine genotypes, NKRN59.58, Derby, Markies, Sifra, 395017.229, Nakpot 5, 20108.5, Royal and 393220.54, had Ryadg gene for PVY resistance and two genotypes, Kimuri and 319919.3, had Rysto gene for resistance to PVY and PVA. Nine genotypes, 395011.2, Markies, Nakpot 5, 20108.5, Sifra, 20157.6, Royal, 2015.8 and Ambition, had the Nbtbr gene for resistance to PVX. In addition, 14 genotypes, 395011.2, Markies, Nakpot 5, Sarpouna, 393220.54, 391046.14, Sarpomira, 395077.12, Sifra, 20157.6, Royal, Ambition, Kimuri and Caruso, had the Nsadg gene conferring resistance to PVS. Four genotypes, Markies, Sifra, Nakpot 5 and Royal, had the Ryadg, Nbtbr and Nsadg genes for combined resistance to PVY, PVX and PVS. The resistant genotypes could be used as parents to introgress resistance genes into susceptible cultivars.

Monoclonal antibody-based serological detection of potato virus M in potato plants and tubers

Potato virus M (PVM) is one of the common and economically important potato viruses in potato-growing regions worldwide. To investigate and control this viral disease, efficient and specific detection techniques are needed. In this study, PVM virions were purified from infected potato plants and used as the immunogen to produce hybridomas secreting PVM-specific monoclonal antibodies (MAbs). Four highly specific and sensitive murine MAbs, i.e., 1E1, 2A5, 8A1 and 17G8 were prepared through a conventional hybridoma technology. Using these four MAbs, we have developed an antigen-coated plate (ACP)-ELISA, a dot-ELISA and a Tissue print-ELISA for detecting PVM infection in potato plants and tubers. PVM could be detected in infected potato plant tissue crude extracts diluted at 1:10240 (w/v, g mL–1) by the dot-ELISA or at 1:163 840 (w/v, g mL–1) by the ACP-ELISA. The Tissue print-ELISA is the quickest and easiest assay among the three established serological assays and is more suitable for onsite large-scale sample detection. Detection results of the field-collected samples showed that PVM is currently widespread in the Yunnan and the Heilongjiang provinces in China. The field sample test results of the developed serological assays were supported by the results from RT-PCR and DNA sequencing. We consider that the newly established ACP-ELISA, dot-ELISA and Tissue print-ELISA can benefit PVM detection in potato plant and tuber samples and field epidemiological studies of PVM. These assays can also facilitate the production of virus-free seed potatoes and breeding for PVM-resistant potato cultivars, leading to the successful prevention of this potato viral disease.

Pest categorisation of potato virus M (non-EU isolates).

Following a request from the EU Commission, the Panel on Plant Health has addressed the pest categorisation of non‐EU isolates of potato virus M (PVM). The information currently available on geographical distribution, biology, epidemiology, potential entry pathways, potential additional impact compared to the current situation in the EU and availability of control measures of non‐EU isolates of PVM has been evaluated with regard to the criteria to qualify as a potential Union quarantine pest. Because non‐EU isolates of PVM are absent from the EU, they do not meet one of the requirements to be regulated as a regulated non‐quarantine pest (RNQP) (presence in the EU); as a consequence, the Panel decided not to evaluate the other RNQP criteria for these isolates. Populations of PVM can be subdivided into two strains: the ordinary strain (PVM‐O) is present in the EU, while the divergent strain (PVM‐D) is absent from the EU or considered to have at most a limited distribution in the EU. Non‐EU isolates of PVM‐O are not expected to have an additional impact in the EU compared to EU isolates and therefore do not meet the corresponding criterion to qualify as a potential Union quarantine pest. The Panel is unable to conclude on the potential impact of non‐EU PVM‐D isolates in the EU territory, but PVM‐D isolates meet all the other criteria to qualify as a potential Union quarantine pest.