Elimination of viruses and hypersensitivity to potato virus Y (PVYo) in an important sudanese potato stock (Zalinge)

Viruses that infect naturally an important Sudanese potato stock Zalinge were detected using enzyme-linked immunosorbent assay, immunosorbent electron microscopy and sap-inoculation to test plants. All of the 19 plants of Zalinge tested were infected with potato leaf roll virus (PLRV) and potato virus S (P VS), and five plants also with potato virus X (PVX). No potato virus Y (PVY), A (PVA) nor M (PVM) were found. The viruses were eradicated with thermo and chemotherapy using standard procedures. The combination of both therapies did not result in any virus-free plants, but resulted in poor plant survival. Thermotherapy reduced the incidence of PLRV and PVS by 45% and 50%, respectively, and one virus-free plant was obtained. It grew vigorously in the greenhouse, was symptomless and had a significantly increased tuber yield compared to the virus-infected plants. Following sap-inoculation with PVY^O, Zalinge showed mosaic symptoms, developed necrosis in the leaves and stem and died 14 days post-inoculation. However, the plants of Zalinge infected with PVY^N remained symptomless, which suggested that hypersensitivity was specific to PVY^O. The fast development of lethal necrosis following infection with PVY^O may contribute to the low incidence of PVY in Zalinge in the field in Sudan.     

湖南省马铃薯主产区马铃薯病毒种类及流行分析

马铃薯是世界第四大粮食作物,其病毒病危害严重。2010年对湖南马铃薯主产区采集的66个病毒标样进行了RT-PCR检测,结果表明,检测出的马铃薯病毒有马铃薯Y病毒(PVY)、马铃薯卷叶病毒(PLRV)、马铃薯X病毒(PVX)、马铃薯S病毒(PVS)、马铃薯A病毒(PVA)和马铃薯纺锤块茎类病毒(PSTVd)。其中PVS的检出率最高,为54.5%,其次是PVX,检出率为45.5%,PVY的检出率为39.4%,PSTVd和PVA的检出率均为21.2%,PLRV的检出率为18.2%。2~4种病毒的复合侵染现象较为普遍。PVY中重组型PVY占85.7%。     

A simple assay system incorporating monoclonal antibodies for the detection of potato virus T

Summary Two monoclonal antibodies (McAbs) which react specifically with potato virus T (PVT) were produced and tested for cross reactivity with potato viruses (A, S, X, Y^o, Y^N, leaf roll), apple stem grooving virus (ASGV) and against healthy sap. They were found to be highly specific for PVT. These two McAbs form the basis of an enzyme-linked immunosorbent assay (ELISA) for the detection of PVT in infected plant material which is of key significance for potato quarantine.     

New isolates of the necrotic strain of potato virus Y (PVYN) found recently in Poland

Summary In comparison to the previously known isolates of potato virus Y^N (PVY^N), some isolates found in Poland since 1984 are more infectious to potato plants, reach faster a higher concentration and induce milder disease symptoms. Potato cultivars resistant to the standard type of PVY_N may be susceptible to the new isolates whereas those that are extremely resistant to PVY remain extremely resistant to the new isolates. The potato cultivar Elipsa is suitable for the differentiation of PVY^N isolates.     

A contribution to the maintenance of phytopathogenic virus strains on tissue culture plantlets

Summary The long-term maintenance of phytopathogenic viruses on potato and tobacco tissue culture plantlets was investigated. Several strains of PVY^N, PVY^O, PVX, PVA, PVM, PVS and PLRV have been kept in a tissue culture type collection of viruses at the Institut für Kartoffelforschung Gross Lüsewitz for 1–3 years. The serological and biological activity of cultures established in vitro of PVY^N-D 884/Solanum tuberosum cv. Ackersegen, PVY^O-1427/Nicotiana tabacum cv. Samsun, PVX-Erstling/Nicotiana tabacum cv. Samsun and PVX-Erstling/Solanum tuberosum cv. Arkula was proved.     

Importance and control of potato virus YN (PVYN) in seed potato production

Summary The tobacco veinal necrosis strain of potato virus Y (PVY^N) first became epidemic in several European countries in the 1950s. To prevent PVY^N-infections, account must be taken of virus sources both within and without potato fields; for forecasting, the aphid vector species, their vector efficiency, and their flight activity must all be known. Well-timed haulm destruction needs knowledges of PVY^N-translocation in potato plants and of the development of mature plant resistance. For successful virus control, also reliable methods for virus detection are needed, and for this ELISA has been well established for many years in seed potato certification schemes. A combined treatment of mineral oil and pyrethroids reduces aphid populations and the spread of stylet-borne viruses in the fields. In breeding for resistance, the major gene Ry induces complete protection against infections of all known PVY-strains.     

Use of jet injection to determine potato cultivar susceptibility to potato viruses A and Yc

Summary The use of a high pressure jet injector to inoculate virus rapidly was compared with graft inoculation to determine cultivar susceptibility to potato virus A (PVA) and potato virus Y^c (PVY^c). Tubers were injected with virus infected potato sap, plant reactions recorded, and virus recovered using a bioassay test and enzyme linked immuno-sorbent assay. The injection method compared well with a traditional grafting procedure for PVY^c susceptibility tests but was unsuitable for testing susceptibility to PVA.     

Translocation of the potato viruses YN and YO in some potato varieties

Summary In experiments on the rate of translocation of the potato viruses Y^N and Y^O in the varieties Bintje, Eigenheimer, Doré and Sirtema it was found that both viruses infect tubers of Bintje much more readily than those of Eigenheimer. The tubers of the four varieties proved to be infected by PVY^N to a higher degree than by PVY^O. Tubers of the variety Doré became infected by PVY^N to a very high degree, whereas the PVY^N infection of those of the variety Sirtema reached the same level as Bintje tubers. Mature plant resistance could be demonstrated with respect to both viruses, but it was much more pronounced in the experiments with PVY^O than in those with PVY^N.     

Census Report of the <Emphasis Type="BoldItalic">Potato Virus Y</Emphasis> (PVY) Population in Swiss Seed Potato Production in 2003 and 2008

The status of the Potato virus Y (PVY) in Swiss seed potato production was investigated in the years 2003 and 2008 by analysing 385 leaf samples of field-grown, suspicious potato plants collected in four representative seed control fields. Serological investigations by ELISA showed that in c. 84% of the PVY-positive samples in both years, viruses belonging to the PVY^N group were found. All 124 serologically positive PVY samples collected in 2003 and a selection of 81 isolates of 2008 were further typified by molecular tests and by biological assays on tobacco and potato plants. These tests largely confirmed the predominance of the PVY^N group and, within this group, the prevalence of recombinant PVY^NTN, with 81.4% and 70.4% in 2003 and 2008, respectively. The percentage of PVY^N-Wilga (PVY^N-Wi) increased from c. 6% to 17% between the two years. PVY^O was detected only in 10.5% and 4.9% of all molecularly analysed samples in 2003 and 2008, respectively. The persistent predominance of recombinant PVY^NTN in Swiss seed potatoes indicates that this strain group is now widespread, representing a considerable threat to Swiss seed potato production.     

Studies on the etiology of tuber necrotic ringspot disease in potato

Summary Potato virus M (PVM), potato virus S (PVS), potato virus X and tobacco veinal necrosis strain of potato virus Y (PVY^R) were isolated from potatoes showing tuber necrotic ringspot disease (TNRD). Potato mop-top virus, tobacco rattle virus, tobacco necrosis virus and tomato black ring virus could not be isolated from the diseased plants. Because PVM and PVS could be isolated from potato plants that did not show symptoms, these viruses could not be causally related to TNRD. However, TNRD is closely connected with infections by PVY^R which always could be isolated from potato plants with TNRD symptoms.

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Zusammenfassung Aus Kartoffelpflanzen (Solanum tuberosum, Sorten Adema, Malacsinka, Mona Lisa, Romano und Rosalie) die Symptome des Tuber necrotic ringspot zeigten, wurden Kartoffel-M-Virus (PVM), Kartoffel-S-Virus (PVS), Kartoffel-X-Virus (PVX) und Kartoffel-Y-Virus (PVY) isoliert. Die Viren wurden mit Hilfe von Differentialwirten, Elektronenmikroskopie, Serologie und Pr?munit?tstests identifiziert. Die untersuchten Kartoffelknollen zeigten deutlich sichtbar nekrotische Ringsymptome (Abb. 1). Von den Nekrosen aufweisenden Knollen und von Kartoffelpflanzen konnten von allen Sorten drei Viren (PVM, PVS, PVY) isoliert werden, von der Sorte Malacsinka zus?tzlich noch PVX (Tab. 2). Entsprechend den Symptomen der Testpflanzen (Tab. 3) identifizierten wir die Virus-isolate aus Kartoffelpflanzen die Symptome des Tuber necrotic ringspot aufwiesen als PVM, PVS, PVX und PVY. Aus keiner kranken Pflanze konnte Kartoffelbüscheltrieb-Virus, Tabakmauche-Virus, Tabaknekrose-Virus und Tomatenschwarzring-Virus isoliert werden. Da PVM und PVS aus Pflanzen, die keine Symptome aufwiesen, isoliert werden k?nnten, k?nnen diese beiden Viren nicht urs?chlich mit den Symptomen der Tuber necrotic ringspot Krankheit (TNRD) verbunden sein. Wir konnten jedoch eine enge Verbindung zwischen TNRD und der Infektion mit PVY feststellen, da dieses Virus von allen Pflanzen, die Symptome des TNRD aufwiesen, isoliert werden konnte. Die Eigenschaften von PVY-Isolaten aus Knollen, Bl?ttern und Wurzeln ?hnelten jenen, die in verschiedenen Testpflanzen gefunden wurden (Tab. 4). Die typischen Symptomreaktionen aufNicotiana debneyi (Abb. 2) undN. tabacum Sorte Xanthi-nc sowie aufSolanum demissum A6-Hybride lassen vermuten, dass die Ursache ein Tobacco veinal necrosis—Stamm des PVY, (PVY^R, siehe Abb. 3) war. Es ist schwierig zu einem endgültigen Ergebnis über die ?tiologie der TNRD zu kommen, weil einige PVY^R-isolate sogar aus symptomlosen Kartoffelknollen gewonnen werden konnten. Die Untersuchungen werden fortgesetzt.

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Résumé Les virus M (PVM), S (PVS), X (PVX) et Y (PVY) sont isolés à partir de plantes de pommes de terre (Solanum tuberosum cvs Adema, Malacsinka, Mona Lisa, Romano et Rosalie) présentant des sympt?mes de taches nécrotiques annulaires. Les virus sont identifiés à l'aide d'h?tes différentiels, de la microscopie électronique, de la sérologie et de tests de protection croisée. Les tubercules examinés présentent des taches nettement visibles de nécroses annulaires (fig. 1). A partir des tubercules nécrosés et des plantes, trois virus (PVM, PVS, et PVY) sont isolés pour tous les cultivars à l'exception de cv. Malacsinka pour lequel PVX est également isolé (tabl. 2). Les sympt?mes révélés sur les plantes tests (tabl. 3) indiquent que les virus isolés à partir des plantes présentant des sympt?mes de nécroses annulaires sur tubercules sont PVM, PVS, PVX et PVY. Les virus du Mop-Top de la pomme de terre, du rattle du tabac, de la nécrose du tabac et des taches noires en anneau de la tomate n'ont pu être isolés d'aucune des plantes malades. Puisque PVM et PVS peuvent être isolés de plantes de pommes de terre ne présentant pas de sympt?mes, ces deux virus ne peuvent être directement responsables des sympt?mes de taches nécrotiques annulaires sur tubercules (TNRD). Cependant, une relation étroite entre TNRD et la contamination par PVY est établie, puisque ce virus peut être isolé de toutes les plantes présentant des sympt?mes de TNRD. Le tableau 4 regroupe les caractéristiques de quel-ques cultures pures de PVY isolées à partir de tubercules, feuilles et racines et semblables à celles trouvées dans différentes plantes h?tes. Les sympt?mes typiques surNicotiana debneyi (fig. 2) etN. tabacum cv. Xanthi-nc, ainsi que surSolanum demissum-A6-hybride laissent à penser que l'agent responsable est une souche nécrotique des nervures du tabac de PVY (PVY^R, voir fig. 3). Il est difficile de conclure de fa?on définitive, quant à l'étiologie de la maladie des taches nécrotiques annulaires, car PVY^R peut être également isolé de tubercules ne présentant aucun sympt?me. Des études axées sur l'étiologie de TNRD sont en cours.

     

The development of mature plant resistance in four potato cultivars against aphid-inoculated potato virus YO and YN in four potato cultivars

Summary Field-grown potato plants of cvs King Edward, Record, Maris Piper and Désirée were inoculated on seven different dates during the growing season of 1987 and 1988 with either potato virus Y^O (PVY^O) or PVY^N, using three viruliferous peach-potato aphids (Myzus persicae) per plant. In each cultivar, the proportion of progeny tubers infected with PVY^O or PVY^N was high in plants inoculated during the four weeks following emergence, the proportion declining to zero or close to zero in the subsequent 4–6 wks.     

Soybean aphid,Aphis glycines Matsumura, a new vector ofPotato virus Y in potato

Soybean aphid (Aphis glycines Matsumura), an exotic species first discovered in the North Central region of the United States in 2000, is a competent vector of severalPotyviridae. Soybean aphid has high fecundity and produces alatae (winged morphs) readily, characteristics typical of proficient virus vectors. When soybean aphids were exposed toPotato virus Y (PVY)-infected potato plants and then clip-caged on healthy potato plants in groups of five or as single aphids, PVY transmission ranged from 14% to 75% across all experiments. PVY^o, PVYⁿ, and PVP^ntn strains were transmitted by soybean aphid.     

Use of the virus strain group concept to characterize the resistance to PVX and PVYo in the potato cv Allegany

Resistance to the potato viruses X (PVX), Y (PVY) and A (PVA) was examined in the potato cv Allegany released by Cornell University in 1990. Standard potato cultivars from North America and Europe were included for characterization of the resistance response. Allegany was extremely resistant to a strain group 3 isolate of PVX and reacted with hypersensitivity to an ordinary strain isolate of PVY (PVY^o). However, Allegany was susceptible to an isolate of PVY causing necrosis in tobacco (PVY^N), and to an isolate of PVA. No symptoms appeared following infection with PVY^N and PVA. Identification of existing virus strain groups in a geographic area is an important aspect of predicting cultivar response to inoculation in the field.     

Stage of development of leaf and tuber tissue of the potato plant influences the titer of potato virus M

The enzyme-linked immunosorbent assay (ELISA) was adapted for the detection of potato virus M (PVM). Detectability of PVM was influenced by the stage of plant growth and that of the plant part assayed. In young potato plants, one week prior to flowering, PVM titer was relatively high (0.77 A_405nm units) in the basal leaves and barely detectable (0.09 A_{405 nm} units) in the top leaves. In mature plants, two weeks prior to harvesting, top leaves contained more virus (0.34 A_{405 nm} units) than middle (0.24 A_405nm units) or basal leaves (0.15 A_{405 nm} units). In rapidly growing tubers PVM content was higher (1.57 A_{405 nm} units) than that in fully grown tubers (0.71 A_405nm units) whereas the virus was not detectable in the mother tuber four weeks following planting. PVM was reliably detected when disks from intact leaves were substituted for leaf extracts as the test sample     

Transmission of potato leaf roll virus byMyzus persicae (Sulz.) from leaves and plants of different ages

Summary Young potato plants were a better source of potato leaf roll virus (PLRV) for aphids,Myzus persicae (Sulz.), than old ones. For plants 6, 7.5 and 9 weeks old, the best sources of PLRV were the lower, middle and upper leaves, respectively. The frequency of PLRV transmission from upper leaves did not change much with increasing age of plants nor did it change with different leaflets from the same leaf.     

Inheritance of extreme resistance to potato virus Y in potato

Summary Segregation for extreme resistance to PVY was evaluated in progenies derived from crossing two extremely resistant potato clones with parents differing in resistance. Resistance was evaluated after mechanical inoculation with PVY^O and PVY^N, and after graft inoculation with PVY^O. Biological and serological tests (ELISA) were used for virus detection. The extreme resistance is governed by a single dominant gene, but observed segregations deviated from the expected ratios. Considerable modifying effects were detectable, depending on the potato genotype and virus isolate, for a significant excess of susceptible genotypes was observed in some progenies. Moreover, genotypes with non-parental types of resistance to PVY were observed.     

Response of potato cultivars to North American isolates of PVYNTN

Potato cultivars were assessed for their sensitivity to potato tuber necrotic ringspot disease (PTNRD) induced by two North American isolates (Tu619 and Tu660) of the tobacco veinal necrosis strain of potato virus Y (PVY^N) and belonging to the tuber necrosis (PVY^NTN) sub-group. Several widely grown cultivars (e.g. Norchip and Ranger Russet) were found to be highly sensitive to PTNRD, while others (e.g. Russet Burbank, Russet Norkotah and Shepody) were not. The foliage symptoms induced by these isolates were distinct from those reported to be produced by European isolates of PVY^NTN, in that systemic necrotic rings and chlorophyll figures on the leaves were not produced. Instead, the symptoms were similar to those of normal strains of PVY^N. The apparent correlation between resistance to the PVY^O (common) strain group and cultivar sensitivity to PTNRD is discussed.     

Evaluation of the enzyme-amplified ELISA for the detection of potato viruses A,M, S,X, Y,and leafroll

Various parameters,e.g. types of microtiter plate for DAS-ELISA (double antibody sandwich-enzyme-linked immunosorbent assay), use of fresh or frozen amplifier solutions for enzyme-amplified-ELISA, and use of sodium diethyldithiocarbamate (NaDIECA) in sample buffer in cocktail-ELISA were evaluated for the detection of potato viruses A, M, S, X, Y and leafroll from potato foliage. Dynatech Immulon immunoplates provided higher readings for all viruses. Fresh amplifier solution in amplifed-ELISA was superior to frozen solutions. Amplified ELISA gave only marginal improvement in the sensitivity over the standard DAS-ELISA. Addition of NaDIECA in sample buffer did not improve the detection of viruses in DAS-, amplified-, or cocktail-ELISA. Cocktail-ELISA can reduce antigen incubation time to as short as 15 min for PVA, PVM and PVX; 1 hr for PVY and PLRV; and 2–4 hr for PVS using pre-coated plates. Although amplified-ELISA is slightly more sensitive than DAS-ELISA for certain potato viruses, it is not suitable for large-scale indexing of potato viruses in Seed Certification Laboratories, in view of the additional steps needed in carrying out this procedure.