First Report of Potato Viruses Infecting Lamium purpureum in Ukraine

Weeds as reservoirs for destructive plant pathogens have a significant impact on the viral epidemiology, ecology and, as a result, on local economy, and are therefore being investigated in many parts of the world. Thus, the aim of this study was to investigate virus occurrence in red dead-nettle plants (Lamium purpureum L.) widespread in urban and field conditions throughout the in the Kyiv region of Ukraine. Methods. Field crop observations, visual diagnosis, biological testing of the virus, immunoassay (ELISA), polymerase chain reaction with reverse transcription (RT-PCR), sanger sequencing of partial genome sequences of PVX, PVY, PVS, PVM. Results. The results obtained in the study indicate that Lamium plants could be alternative weed hosts of number important viral diseases including potatoes and other vegetables. Serological and molecular test results evidence plants were infected by Potato virus X, Potato virus Y, Potato virus M, Potato virus S and therefore Lamium L. species can serve as a potential source of inoculum for wide range of vegetables and ornamentals. This study is the first report of Lamium plants being naturally infected with Potato virus M and Potato virus S in central Europe. Conclusions. These plants are alternative host of mixed infection with viruses belonging to different families: Alphaflexiviridae, Betaflexiviridae and Potyviridae.

One-step real-time multiplex reverse transcription-polymerase chain reaction assay with melt curve analysis for detection of potato leafroll virus, potato virus S, potato virus X, and potato virus Y

Background Certification of seed potato as free of viruses is essential for stable potato production. Among more than 30 virus species infecting potato, potato leafroll virus (PLRV), potato virus S (PVS), potato virus X (PVX), and potato virus Y (PVY) predominate worldwide and should be the targets of a high-throughput detection protocol for seed potato quarantine. Results We developed an assay based on one-step real-time multiplex reverse transcription-polymerase chain reaction (mRT-PCR) with melt curve analysis for the four viruses and one internal control, potato elongation factor 1 alpha gene (EF1α). Virus-specific primers were derived from conserved regions among randomly selected representatives considering viral genomic diversity. Our assay simultaneously detected representative Japanese isolates of PLRV, O lineage of PVS, PVX, and NTN strain of PVY. The variability of melting temperature (Tm) values for each virus was confirmed using Japanese isolates, and virus species could be identified by the values of 87.6 for PLRV, 85.9 for PVX, 82.2 (Ordinary lineage) to 83.1 (Andean lineage) for PVS, and 79.4 (NA-N strain) to 80.5 (O strain and NTN strain) for PVY on average. The reliability of calculation was validated by comparing the calculated Tm values and measured Tm values and the values had a strong linear correlation (correlation of determination: R2 = 0.9875). Based on the calculated Tm values, representative non-Japanese isolates could also be identified by our assay. For removing false positives, two criteria were set for the evaluation of result; successful amplification was considered as 30.0 ≥ threshold cycle value, and the virus-specific peak higher than the EF1α-specific peak was considered as positive. According to these criteria, our assay could detect PLRV and PVS from 100-fold dilution of potato leaf homogenate and PVX and PVY from 1000-fold in a model assay. Conclusion This new high-throughput detection protocol using one-step real-time mRT-PCR was sensitive enough to detect viruses in a 100-fold dilution of singly-virus contaminated homogenate in a model assay. This protocol can detect the four viruses in one assay and yield faster results for a vast number of samples, and greatly save the labor for seed potato quarantine and field surveys.

SPREAD OF POTATO VIRAL DISEASE PATHOGENS IN CULTURE CULTIVATION ZONES

Objective. Monitoring observations over the phytovirological condition of potato planting in different regions of Ukraine, taking into account potato degeneration zones. Methods. Laboratory (virological, immunological, electronic microscopy), field, statistical. Results. The map and diagrams show the results of monitoring studies conducted in 2016–2020, during which 435 varieties of potatoes of Ukrainian and foreign selection were tested. In the zone of the lowest degeneration or the zone with a relatively low degree of infectious load, 100 % spread of pathogenic complexes involving potato virus Y in the Region of Zakarpattia, potato viruses M and Y in the Region of Chernivtsi, ranging from 89 % to 100 %. In the zone of strong degeneration of the culture or the zone with a high degree of infectious load, spread of pathogens of potato viral diseases is from 94 % to 100 %, and the vast majority of viruses belongs to pathogens of severe viral diseases. In the zones of mild and moderate degeneration, which belong to the zones with relatively low degree and with moderate degree of infectious load according to another diagram, potato virus M in monoinfection from 17 % to 50 %, in the pathogenic complex with potato virus S from 8 % to 36 %, with potato virus Y from 6 % to 32 % was detected. In the Region of Kyiv, the spread of potato virus Y+S complex reaches 65 %. In all areas, there is an extremely high level of infection of the culture with potato virus M, which is the cause of severe viral diseases of potatoes. Conclusion. The results of phytovirological monitoring show that the boundaries between potato degeneration zones are smoothed down. Climatic changes, active resettlement of virus vectors, intensification of trade relations with the constant import of foreign potato seed material result in the significant spread of pathogens of potato viral diseases.

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.

In silico Characterization and Homology Modelling of Potato Leaf Roll Virus (PLRV) Coat Protein

Polerovirus (Family-Luteoviridae) are one of the most destructive viruses causing detrimental diseases in vegetable crops in tropical regions of the world including India. Four species viz. potato leaf roll virus (PLRV), potato virus Y(PVY), potato virus X(PVX) and potato virus S(PVS) are known to cause different diseases in potato crops. Of the various viral diseases inflicting potato crops, potato leaf roll disease is the most destructive and widely distributed. They cause huge agro-economical losses (90%) worldwide and thus are the subjects of immense concern. PLRV is a phloem-limited spherical virus transmitted by several aphid species in a persistent manner. A study was performed in order to detect the infection of potato leaf roll virus from different regions of Bihar. These infected samples were diagnosed first using DAS-ELISA for the PLRV infection and later, coat protein was amplified and sequenced from PLRV positive sample. Phylogenetic tree deduced based on the nucleotide sequence of the coat protein gene gene showed a distinct divergence of PLRV isolates in two major clades. The molecular weight of the predicted protein sequence of 203 amino acids was found 22617.06 daltons while theoretical pI was 5.22. The extinction coefficient of predicted coat protein was 0.836. An attempt was taken in order to illustrate the 3D model of the coat protein which was further verified using Ramachandran plot. The model structure obtained using Swiss-Model had 92.9% residues in the most favourable region of the Ramachandran plot (Fig. 3c) and showed Z-score for bond angles, chi-1/chi-2 correlation and Ramachandran Z-score were 1.457, 1.773 and -2.633 respectively which exhibited considerably good model quality.