Evidence for persistent, symptomless infection of some potato cultivars with tobacco rattle virus

Summary Infection with an M-type (particle producing) isolate of tobacco rattle virus (TRV) was detected in leaves and/or roots of some plants from 11 of 13 potato cultivars grown in soil containing viruliferous trichodorid nematodes. Virus was detected in tubers of 8 of 13 cultivars, although only two (Pentland Dell and Maris Bard) developed spraing symptoms. Six cultivars (Arran Consul, Home Guard, King Edward, Romano, Santé and Wilja) were infected with TRV without developing spraing symptoms. Plants grown from virus-containing, symptomless tubers became systemically infected with M-type TRV and produced symptomless infected daughter tubers. Virus was maintained through three generations of vegetative propagation, and the plants were sources for acquisition of the virus by trichodorid nematodes. Distribution of virus in both spraing-affected and symptomless tubers was erratic. Movement of symptomlessly infected seed tubers may be a means of dissemination of the virus and of its introduction to previously unaffected sites.     

Pathogenicity of Washington and Oregon isolates of tobacco rattle virus on potato

Soil samples from corky ringspot (CRS) problem fields of potato in the states of Washington and Oregon were collected and planted withNicotiana tabacum ‘Samsun NN’ tobacco to bait tobacco rattle virus (TRV) and to increaseParatrichodorus allius populations, the vector of TRV. Pathogenicity of three isolates of TRV was assessed on Russet Burbank and Russet Norkotah plants usingP. allius as the vector. The most severe CRS tuber symptoms were with TRV from Pasco, WA, followed by Umatilla, OR, and Mattawa, WA, indicating a distinct variation in virulence among virus isolates. The lowest number ofP. allius that transmitted TRV resulting in CRS symptoms on Russet Norkotah was three nematodes per 250 cm³ soil. When potato plants were exposed toP. allius at different times in their growth, tubers on older plants were more resistant than younger tubers to CRS. Severity of CRS tuber symptoms was correlated with age of potato plants in pot culture. Reproduction ofP. allius on potato roots did not influence the incidence and severity of tubers symptoms. Under similar conditions, Bintje, a variety known to be resistant to CRS, served as a host forP. allius, yet remained asymptomatic. The protocol employed in these studies is appropriate for testing potato germplasm for resistance to CRS.     

Detection of tobacco rattle virus in potato tubers using a simple RT-PCR procedure

Summary A simple assay for detection of tobacco rattle virus in infected tubers involving RT-PCR was developed. The assay detected a wide range of strains, including nonparticle NM variants. RNA extraction methods were compared, and a simple method was found to give reliable results. The method enabled detection of at least 1 ng of tobacco rattle particles in 100 mg tuber extract.     

Development during storage of spraing symptoms in potato tubers infected with tobacco rattle virus

Summary In trials with potato tubers infected with tobacco rattle virus (TRV), symptoms of spraing in cvs Bellona, King Edward, Maris Bard, Matilda, Sv 82146 and Sv 82149 increased during storage when the tubers were cut. Storage of intact tubers at a constant temperature of 9°C or at fluctuating temperatures (2 weeks at 18°C, 2 weeks at 9°C and 2 weeks at 18°C) did not increase the frequency of symptoms.     

Effects of soil fumigation with Telone-C on the field inoculum potential of tobacco rattle virus and potato yields

Two Julesburg sandy-loam fields in Weld County, Colorado, with a history of Corky Ringspot (CRS) caused by tobacco rattle virus (TRV) were injected with Telone-C as fall or spring applications and planted to potatoes. Deep soil sample cores taken from the experimental fields were planted toNicotiana tabacum L. var. Samsun serving as TRV bait and indicator plants. Systemic infection of bait plants and assay of the bait plant roots for TRV indicate that potential TRV inoculum was present which escaped the effects of fumigation treatments. TRV was found to be widely but erratically distributed throughout the experimental fields. The low incidence of CRS in tubers harvested from the treated fields suggests that fumigation may have short term benefits but potential inoculum exists which could lead to infection after the effects of fumigation have dissipated. The total yield of tubers was increased in the two cultivars planted (Norgold and Norland) in the fumigated fields receiving spring or fall applications. The yield of U.S. No 1 Grade potatoes in the Norland cultivar was increased significantly by both fall and spring fumigation. These yield increases were directly related to the reduced incidence ofVerticillium wilt observed in the fumigated soils and reported as a personal communication from unpublished data.     

Diagnosis of tobacco rattle virus (TRV) and other viruses in weed and rotation crops in potato fields

The methodology for the detection of tobacco rattle virus (TRV) and for the incidence of TRV and other viruses was determined in weed species associated with potatoes. Symptoms onNicotiana tabacum L. cv. ‘Samsun NN’and Phaseolus vulgaris L. cv. ‘Bountiful’ were used to detect the viruses. Identity was confirmed by comparison with symptoms produced on plants by standard cultures of TRV and potato virus X (PVX), by electron microscopy, and by serology.Portulaca oleracea L.,Solatium sarachoides Sendt., andAmaranthus retroflexus L. were hosts of TRV; the latter two also carried PVX. Most TRV carriers were found adjacent to infected potatoes. The roots of naturally infectedS. sarachoides contained the highest concentration of TRV encountered in these studies. Mechanical inoculation of TRV to A.retroflexus andS. sarachoides produced variable symptoms that included red spots on the former and chlorosis and stunting on the latter. TRV moved systematically in both species. Assay methods for detection were adequate but low concentrations of TRV limited the usefulness of electron microscopy and serology.     

Weed hosts of the tobacco rattle virus in Idaho

The corky ringspot disease of potato (Solanum tuberosum) caused by the tobacco rattle virus (TRV) is a serious problem in certain Idaho localities. To investigate natural TRV sources, weeds and plants from rotation crops were randomly collected from six fields with a history of corky ringspot symptoms. Transmission trials, Ouchterlony agar double-diffusion tests, and electron-microscopy showed evidence of TRV in three Idaho counties (Fremont, Ada, and Canyon). Inoculations were made from 27 species and TRV was recovered from the roots of three:Solanum nigrum, Brassica campestris, andErodium cicutarium. Solanum nigrum was the most consistent source of TRV and it generally incited the severest symptoms onNicotiana tabacum (Samsun NN). The results show thatS. nigrum, besides being an important wild host of TRV, may be a useful naturallyoccurring bait plant for detection of TRV in field soils.     

Distribution of tobacco rattle virus and potato virus X in leaves,roots, and fruits and/or seeds of naturally-infected weeds

Weeds in tobacco rattle virus (TRV)-infested potato fields were examined for TRV and potato virus X (PVX) with the enzyme-linked immunosorbent assay. Questionable positive reactions were evaluated with immunosorbent electron microscopy. Of 615 weeds, representing 28 species, sampled over a two-year period, four species contained only TRV, three were infected only with PVX and eight had both viruses. Tobacco rattle virus was located only in the roots of five species and PVX was found only in the foliage of five species. Seeds and/or fruits of three species contained TRV while two contained PVX. Only one weed species,Solanum sara choides, contained both viruses in all plant portions tested. Potato virus X was not detected in weeds within a field planted with PVX-free potato seed.     

Symptoms caused by potato virus S (PVS) and tobacco rattle virus (TRV) on detached leaves ofSolanum demissum Y

Summary Detached leaves ofSolanum demissum Y produced clear dark green and light brown necrotic ring spots 5–6 days after mechanical inoculation with PVS and dark brown necrotic rings and line patterns 6–7 days after inoculation with TRV. It appears to be a useful test plant for the detection of both viruses.     

Influence of post harvest temperature treatments,storage period and harvest date on development of spraing caused by tobacco rattle virus and potato mop-top virus

Summary The frequency of PMTV-spraing and TRV-spraing increased during storage in several cultivars. The only exception was cv. Saturna, where a decrease was observed in 1992. A spraing inducing treatment of one week at 18 °C followed by one week at 8 °C immediately after an early harvest increased the frequency and provided a rough estimate of the development of spraing in untreated tubers during storage. Under most circumstances wound healing at 25 °C compared with 15 °C resulted in a lower frequency of spraing during the storage period. The date of harvest had an important influence on development of spraing during storage and on the effect of post harvest temperature treatments. Therefore, physiological processes that induce or erase spraing are strongly related to tuber maturity. The mechanisms controlling development of symptoms seemingly are identical for the two spraing inducing vira.     

Weed hosts ofParatrichodorus allius and tobacco rattle virus in the Pacific Northwest

The ability of several weed species to serve as hosts for tobacco rattle virus (TKV), the causal agent of corky ringspot disease of potato (CRS), and its nematode vector,Paratrichodorus allius, was investigated in greenhouse studies. ViruliferousP. allius multiplied on 24 out of 37 weed species tested, indicating they were suitable hosts of the vector. However, only 11 of these weeds were infected with TRV, as determined by ELISA. The nonhost status of a given weed species was not changed whether the viruliferous vector population originated from CRS problem fields in WA, OR, or ID. Several weeds served as hosts for the vector and virus including kochia, prickly lettuce, henbit, nightshade species (black, hairy, and cutleaf), common chickweed, and annual sowthistle. Virus-freeP. allius acquired TRV from the three nightshade species, volunteer potato grown from TRV-infected tubers, and prickly lettuce, and subsequently transmitted the virus to ‘Samsun NN’ tobacco indicator plants. Thus, some weeds may play a role in the epidemiology of CRS by perpetuating TRV and its vector in a problem field.     

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.     

Reactions of various plant species to inoculation with potato aucuba mosaic virus

Summary Inoculation with PAMV produced local lesions inGomphrena globosa andPhaseolus vulgaris cv. Bruine stam.Browallia americana, B. viscosa, Cyphomandra betacea, Melilotus indicus, Lycopersicon pimpinellifolium, Nicotiana amplexicaulis, N. clevelandii, N. maritima, N. nudicaulis, N. setchellii andN. solanifolia were symptomless hosts.Melilotus sulcatus was not susceptible. Sugar pea cultivars included in our experiments were better local-lesion hosts than the common pea cultivars. Although severity of symptoms differed with the virus isolate, it was not possible to distinguish PAMV isolates with seed-grown hosts. Using a range of potato cultivars was more reliable. A recently found isolate of PAMV, which did not induce symptoms in potato cv. Record, behaved similarly to other isolates on the above-mentioned species.

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Zusammenfassung Kürzlich wurde eine symptomlose Kartoffelpflanze, Sorte Record, gefunden, bei der sich herausstellte, dass sie mit Kartoffel-Aucubamosaikvirus (PAMV) befallen war. Es wurden Untersuchungen gemacht, um festzustellen, welche Pflanzenarten für die Bestimmung der PAMV-St?mme benützt werden k?nnen und ob das neue Isolat auch in andern Kartoffelsorten symptomlos sein würde. Der Einfluss des Isolats aus der Sorte Record wurde mit Isolaten aus den Sorten Albion, Friso, Gloria, May Queen und Triumf verglichen. In Tabelle 1 sind Pflanzenarten aufgeführt, die für fie sechs verwendeten Virusisolate nicht empf?nglich sind. In unsern Versuchen warenAmaranthus gangeticus, Atropa belladonna, Celosia christata, Stellaria media undTetragonia expansa ebenfalls nicht empf?nglich, obwohl andere Forscher behaupteten, das Gegenteil bewiesen zu haben. Entgegen den Feststellungen von Kollmer & Larson (1960) und in Uebereinstimmung mit Hollings (1959) ermittelten wirGomphrena globosa als Testpflanze für Lokall?sionen von PAMV. Alle untersuchten Sorten von Zuckererbsen waren Testpflanzen für Lokall?sionen von suchten gew?hnlichen Erbsensorten (Tabellen 2, 3). Die Bohnensorte Bruine stam entfaltete Lokall?sionen 6–7 Tage nach der Inokulation mit jedem der sechs PAMV-Isolate bei einer Temperatur von 20°C (Abb. 3). PAMV wurde übertragen aufBrowallia americana undB. viscosa; Cyphomandra betacea, Lycopersion pimpinellifolium, Nicotiana amplexicaulis, N. clevelandii, N. maritima, N. nudicaulis, N. setchellii, N. solanifolia, Melilotus indicus. M. sulcatus war nicht empf?nglich. Obwohl es kleine Unterschiede in der St?rke der Symptome, die von den verschiedenen Isolaten ausgel?st wurden, gab, wurden in samenbürtigen Testpflanzen im allgemeinen ?hnliche Symptome erzeugt. Das Isolat PSN₁ ist irgendwie aussergew?hnlich. InNicotiana tabacum (Abb. 4),N. rustica, N. sylvestris undSolanum integrifolium l?ste dieses Isolat eine lokalnekrotische Reaktion aus. In Tabelle 4 sind die Reaktionen von verschiedenen Kartoffelsorten nach mechanischer Inokulation mit PAMV aufgeführt. Es wird gezeigt, dass das Isolat aus der Sorte Record nicht in allen Kartoffelsorten symptomlos ist. Aus den Ergebnissen in Tabelle 4 kann geschlossen werden, dass das Symptombild in den Sorten Bintje, Record und Surprise genügend Information bietet, um zu entscheiden, um welches PAMV-Isolat es sich handelt. Zum Nachweis des PAMV ist jedoch immer noch der Lokall?sionenwirtCapsicum annuum die geeignetste Testpflanze. Schliesslich wird eine Uebersicht über die Testpflanzen, die für PAMV empf?nglich sind, gegeben (Tabelle 5).

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Résumé Récemment on a trouvé und plante de Record sans sympt?me qui devint infectée avec le virus de mosa?que Aucuba (PAMV). Des recherches furent entreprises pour découvrir quelle espèce de plante pouvait être utilisée pour l’identification de souches de PAMV et trouver si le nouvel isolat serait sans sympt?me aussi chez d’autres variétés de pomme de terre. On a comparé l’effet de l’isolat de Record avec celui d’isolats de Albion, Friso, Gloria, May Queen et Triumf respectivement. Le tableau 1 présente les espèces de plantes qui ne sont pas susceptibles aux six isolats de virus utilisés. Selon nos essais,Amaranthus gangeticus, Atropa belladona, Celosia christata, Stellaria media, Tetragonia expansa ne sont pas susceptibles non plus, quoique d’autres chercheurs ont dit avoir prouvé le contraire. Contrairement aux découvertes de Kollmer et Larson (1960) et en accord avec Hollings (1959), nous trouvons queGomphrena globosa est un h?te à lésions locales pour PAMV. Toutes les variétés de pois sucrés testées sont des h?tes à lésions locales pour PAMV. Ceci n’est pas vrai pour toutes les variétés communes de pois testées (tableaux 2, 3). La variété de haricot ‘Bruine Stam’ développe des lésions locales 6–7 jours après inoculation avec chacun des six isolats PAMV quand elle est conservée à 20°C (fig. 3). PAMV est véhiculé parBrowallia americana. B. viscosa, Cyphomandra betacea, Lycopersicon pimpinellifolium, Nicotiana amplexicaulis, N. clevelandii, N. maritima, N. nudicaulis, N. setchellii, N. solanifolia, Melilotus indicus. M. sulcatus n’est pas susceptible. Quoiqu’il y ait de légères différences dans la sévérité des sympt?mes induits par les différents isolats, des sympt?mes en principe semblables sont produits dans les h?tes provenant de semence. L’isolat PSN₁ est quelque peu exceptionnel. DansNicotiana tabacum (fig. 4),N. rustica, N. sylvestris etSolanum integrifolium, cet isolat induit une réaction nécrotique locale. Le tableau 4 présente les réactions de diverses variétés de pomme de terre après inoculation mécanique avec PAMV. Il est montré que l’isolat de Record n’est pas sans sympt?me chez toutes les variétés de pomme de terre. Des résultats présentés dans le tableau 4 on peut conclure que l’expression symptomatique chez les trois variétés Bintje, Record et Surprise donnerait une information suffisante pour décider quel isolat est en cause. Cependant l’h?te à lésions locales,Capsicum annuum est toujours la plante test la plus convenable pour la détection du PAMV. Finalement l’auteur présente une nomenclature des h?tes susceptibles (tableau 5).

     

Dormancy and sprout development of some South African potato cultivars during cold storage

Summary Observations were made on dormancy and sprout growth of nine potato cultivars stored at 3–4°C, 7–8°C and 11–12°C, respectively. Tubers of the cultivar Vanderplank had a very long dormant period (232 days at 3–4°C) and showed little sprout growth at 180 days. The cultivar Koos Smit had a very short dormant period (92 days at 3–4°C) and developed considerable sprout growth at the higher temperatures. The reaction of tubers of Up-to-date and BP₁ were approximately the same, and intermediate between those of Vanderplank and Koos Smit.     

Assessment of new potato cultivars in Europe: a survey

Summary In 1994, a postal questionnaire was sent to 41 institutes in 27 countries to obtain information on the national potato cultivar testing programmes in Europe. Responses were received from 19 countries. Foliage, tuber and yield characteristics were assessed in all countries but the number of sites and replicated varied considerably between the countries. Cooking and taste qualities were measured in most countries using relatively simple methods but processing characteristics were tested less commonly. Susceptibility to the most common diseases, i.e. late blight, common scab, leafroll and PVY^o, was assessed in over 75% of the countries while resistance to another 21 disease and 4 potato cyst nematode pathotypes was assessed by various countries, depending on their national importance. Many of the assessments were based on records of natural infection although controlled inoculation tests were done more frequently for the more important diseases.