Evaluation of tuber-bearingSolanum species for symptomology,as diagnostic hosts,and sources of immunityto potato virus Y necrotic strain (PVYN)

A total of 258 Plant Introductions (PI) belonging to 69Solarium species were evaluated in the greenhouse for their reaction to the tobacco veinal necrosis strain of potato virus Y (PVY N). One hundred and thirty-one (50.7%) of the PI accessions produced mosaic symptoms ranging from mild to severe. Local lesion and veinal necrosis symptoms were observed in 19 PI accessions (7.3%) and a variety of other symptoms were observed in another 11 PI accessions (4.2%). Only 97 PI accessions (37.5%) were symptomless carriers of PVY^N. PI accession 473505 ofS. sparsipilum and PI accession 498021 ofS. brachycarpum developed local lesions and veinal necrosis with PVY^N, but necrotic spots and mosaic with PVY^o. Common mechanically-transmitted potato viruses A, S, M, and X did not interfere with PVY symptom development inS. sparsipilum andS. brachycarpum. Thus, PI 473505 and PI 498021 can be used as indicator plants for specific identification of PVY^N. PI accession 472819 ofS. chacoense developed local lesions with systemic spread in PVY^o, but without systemic spread in PVY^N. Thus, this can be used as a differential host plant for PVY strains. Two PI accessions ofS. stoloniferum, PI 160372 and 161171 were immune to PVY^N.     

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.     

Protection against potato virus Y (PVY) in the field in potatoes transformed with the PVY P1 Gene

Lines of potato cv. Pito transformed with the P1 gene ofPotato virus Y (PVY^o) in sense or antisense orientation were evaluated for resistance to PVY in the field in 1997 and 1998. The transgenic resistance fully protected the crop from infection with PVY^o transmitted by aphids in both years. These plants were not resistant to the field isolates of the PVY^N strain group, which is in agreement with our greenhouse experiments. Consequently, several transgenic lines produced higher yields than the nontransgenic cv. Pito plants. These results showed that the P1 gene-mediated resistance provides significant benefits under conditions were the incidence of infections and damage by PVY^o are considerable.     

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.     

Spread of potato virus Y (PVY) in relation to aphid population trends in potato fields in Israel

Summary Test of field spread of potato virus Y (PVY) were carried out in the coastal plain of Israel during the autumn growing seasons of 1964 and 1965. These included twice-weekly samplings of the winged aphid population. PVY-infected tubers of the varietyUp-to-Date, were planted at predetermined points in a trial plot, simultaneously with PVY-free ones. Virus spread to progeny was determined by indexing plants grown from tubers that had been collected at different distances from the infector plants. In 1965, a fair correlation was established between the incidence of naturally-spread PVY and distance from the source of inoculum. In 1964, however, the number of aphids trapped were exceptionally high, resulting in a PVY incidence more than double that of 1965 but with practically no apparent relation to the distance from the infector plants. This can be partly explained by the additional infection arising from sources outside the trial plot through the activity of an increased number of vector individuals.

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Zusammenfassung Im Anschluss an Studien über die Feldausbreitung von PVY, die vor 7 Jahren begannen, wurden in der Küstenzone von Israel w?hrend der zwei Herbstanbauperioden 1964 und 1965 besondere Untersuchungen angestellt. Halbw?chentlich wurden die geflügelten Individuen der Familie Aphididae in der Versuchsparzelle mit Hilfe der Moericke-Falle gesammelt. Vom gesamten Fang wurde nurMyzus persicae identifiziert, da diese Art der Hauptübertr?ger des PVY in Israel ist. Knollen der SorteUp-to-Date, mit dem gew?hnlichen Isolat von PVY infiziert, wurden an vorher bestimmten Stellen der Versuchsparzelle gleichzeitig mit PVY-freien Knollen gepflanzt (Abb. 1) Das Auftreten des Virus auf Knollen der neuen Generation wurde auf folgende Weise festgestellt: Knollen, die in verschiedenen Entfernungen von der Inokulumquelle gesammelt wurden, wurden in der Augenstecklingsprüfung nicht nur visuell beurteilt, sondern auch im A6-Test (Einreiben von Blattsaft) und mittels verschiedenen Testpflanzen überprüft. Zu diesem Zweeke wurden Stecklinge unter insektenfreien Bedingungen angezogen. Im Herbst 1965, wie auch in den Frühjahren 1960 und 1961 und im Winter 1961 (Zimmerman-Gries undNitzany, 1964), wurde eine ziemlich gute Korrelation zwischen Feldauftreten des PVY und der Entfernung von der Inokulumquelle beobachtet (Abb. 2). Im Jahre 1964 waren die Fallenergebnisse aussergew?hnlich gross. Dies nun verursachte ein mehr als doppelt so starkes Auftreten von PVY wie im Jahre 1965, und dies stand praktisch in keiner augenscheinlichen Wechselbeziehung zur Entfernung von der ausgepflanzten Inokulumquelle (Abb. 2). Das Verwischen eines solchen Korrelationsbildes im Jahre 1964 wird teilweise durch die weitere Ansteckung erkl?rt, die, von Quellen ausserhalb der Versuchsparzellen kommend, durch die vermehrte Zahl von übertr?gerindividuen (Abb. 3), die im Felde vorhanden waren, verursacht wurde.

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Résumé Des recherches particulières ont été effectuées dans la zone c?tière d'Isra?l durant les deux saisons automnales de culture 1964 et 1965, en jonction à des études sur la propagation au champ du PVY qui débutèrent il y a sept ans. Les individus ailés de la famille des Aphides étaient récoltés dans les parcelles d'essais deux fois par semaine, au moyen de pièges de Moericke. Parmi toutes les captures seuls les puceronsMyzus persicae étaient identifiés, puisque cette espèce est le principal transmetteur du PVY en Isra?l. Des tubercules de la variétéUp-to-Date, infectés avec l'isolat ordinaire de PVY, ont été plantés à des emplacements déterminés à l'avance dans la parcelle d'essais en même temps que les tubercules libres de PVY (Fig. 1). La présence du virus sur les tubercules de la génération suivante fut déterminée de la fa?on suivante: aux tubercules récoltes à diverses distances de la source d'infection était appliqué le test de bouture d'oeil de même que le test sur folioles détachées de l'hybride pomme de terre A6, comme aussi sur une séric de plantes-test. Pour la réussite de l'épreuve les pousses de tubercules étaient élevées dans des conditions libres de pucerons. En automne 1965, comme au printemps 1960 et 1961, et en hiver 1961 (Zimmerman-Gries etNitzany, 1964), on a observé une corrélation passablement bonne entre l'apparition au champ du PVY et l'eloignement de la source d'inoculum (Fig. 2). En 1964, les produits des pièges étaient exceptionellement élevés. Ce qui, dès lors, occasionna une apparition de PVY à un degré plus que double de celui de 1965, et engendra aussi ce fait que pratiquement il n'y avait aucune corrélation avec l'éloignement des sources d'inoculum plantées (Fig. 2). Cet effacement d'une telle image de corrélation en 1964 sera partiellement expliquée par une contagion plus grande causée par le nombre accru d'individus vecteurs (Fig. 3) qui étaient présents dans les champs, à partir de sources extérieures aux parcelles d'essais.

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Contribution from the National and University Institute of Agriculture, Rehovot, Israel. 1966 Series, No. 1051-E.

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Paper read to the Virology Section of the Third Triennial Conference of the European Association for Potato Research, Zürich, September 1966.     

Oxygen and carbon dioxide treatment to break potato tuber dormancy for reliable detection of potato virus Y (PVY) by enzyme-linked immunosorbent assay (ELISA)

Summary Dormant tubers of the potato cv. Bintje were treated for 7 or 14 days in an atmosphere enriched to either 40% O₂ plus 1% CO₂, or 40% O₂ plus 20% CO₂, or they were stored in closed plastic bags for identical periods. Rindite-treated and untreated tubers served as references. Treatment with 40% O₂ plus 20% CO₂ for 7 days was nearly as efficient as rindite for inducing sprouting. Both the O₂ plus CO₂ treatments, for 7 and 14 days, considerably increased virus concentration in tubers and had an effect similar to that of rindite 40 days after treatment, but the plastic bag treatment was not as efficient. It is concluded that O₂ plus CO₂ enriched atmospheres could be used for breaking tuber dormancy in order to detect reliably PVY in tuber extracts.     

The relation between aphid flights and the spread of potato virus YN (PVYN) in the Netherlands

Summary In the Netherlands early haulm destruction is the main method of preventing excessive spread of virus diseases in seed potato crops. When potato leaf roll virus was the principal problem, the time of haulm destruction was determined by the flight ofMyzus persicae (Sulzer), studied with the aid of Moericke yellow water traps. As potato virus Y^N became a problem and other aphid species interfered, the interpretation of aphid flights became difficult. An attempt is made to quantify total aphid flight activity in terms of risk to the crop. By attributing relative efficiency factors to 9 vector species and considering their flights as recorded with suction traps, values of vector-pressure are obtained that correlate well with weekly infection of bait plants. If accumulated vector pressures are compared with the flights ofM. persicae as recorded with Moericke traps during 1970–1979, it appears that during 6 of these years the critical periods of both systems coincide. However, in 1974 and 1976 much potential vector threat occurred before the start of the flight ofM. persicae. Suggestions are made as to how to apply the method in practice. A semi-popular account of this paper has appeared in Dutch inGewasbescherming 12 (1981) 57–71.     

Enzyme-linked immunosorbent assay (ELISA) for the detection of potato leafroll virus and potato virus Y in potato tubers after artificial break of dormancy

Summary Conditions necessary for the detection of potato leafroll virus (PLRV) and potato virus Y (PVY) in tubers from primary and secondary infected plants were investigated. Tubers were analysed before and after breaking dormancy by rindite treatment. PLRV was reliably detected indormant tubers whereas PVY was readily detected only when tubers had been rindite-treated and held for two to three weeks at 22°C and high humidity in the dark. PLRV occurred in higher concentration at the heel end than at the rose end of infected tubers and the concentration remained nearly unchanged during the experimental period of 35 days, whereas PVY was found to be more concentrated at the rose end and was rapidly accumulating in the tubers after the break of dormancy. In dormant tubers PVY concentration dropped during storage at 22°C. The use of ELISA for tuber indexing is discussed.     

Reevaluation of the potato aphid,Macrosiphum euphorbiae (Thomas), as vector of potato virus Y

The effectiveness of the potato aphid,Macrosiphum euphorbiae (Thomas), to transmit potato virus Y (PVY) to potato has generally been overestimated because tobacco has been used as the indicator host. Our results demonstrate that, although apterousM. euphorbiae can acquire PVY from potato and tobacco plants and transmit it to tobacco plants, it does not readily transmit it to potato plants. Alatae only transmitted the virus to 4.5% of potato plants. This relative inability to transmit the virus to potato seems independent of potato cultivar. Results suggest that the role of the potato aphid in the spread of PVY in potatoes may be negligible.     

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.     

Guar (Cyamopsis tetragonoloba) as a potential differential host of potato virus Y

Summary Guar is reported for the first time as a host of potato virus Y. The virus produced no symptoms, or occasional faint chlorotic spots on inoculated cotyledons and unifoliate leaves. No symptoms were observed on new growth, but the virus was consistently recovered from these leaves by back-inoculation to tobacco. Neither potato virus X nor cucumber mosaic virus infected guar.     

Kinetin,thermotherapy, and tissue culture to eliminate potato virus (PVX) in potato

PVX infected plantlets from two potato cultivars grownin vitro with 0.3, 3, 30 or 300 ppm kinetin were exposed to temperatures of 28 or 35 C. After 3 wk, axillary buds were isolated and grown aseptically in organogenic media, followed by PVX testing by ELISA. The serological test was also run on whole plantlets at the end of the kinetin-temperature exposure. No donor plants exposed to 28 C nor the plantlets derived from their buds gave an ELISA (-) reaction, regardless of the kinetin content of the media or that of the cultivar. At 35 C the virus was suppressed to undetectable levels in several whole plantlets. In the cultivar Alpha, 2 out of 6 resulting plantlets after isolation of buds were virus-free in the presence of 3.0 mg/1 kinetin during the treatments. From Atzimba, about 15–40% of the regenerated plants were ELISA (-), without any relationship to the cytokinin content in the media. Heat had a stronger influence on virus elimination than kinetin and the results varied with the cultivar.     

Treatments that improve serological detection of potato viruses X,S, M and Y

Summary It was found that addition of an equal volume of 0.2% sodium sulphite or a mixture of sodium sulphite and sodium azide (both 0.2%) to expressed leaf sap improved serological detection of viruses and prevented non-specific reactions. Incubations of the preparations at 20–24°C gave better serological detectability than incubating at 10–12°C. If the sap was centrifuged, better results were subsequently obtained if centrifuging had been done at 4200 or 5900 g than at lower values.     

Reducing the spread of potato leaf roll virus,alfalfa mosaic virus and potato virus Y in seed potatoes by trapping aphids on sticky yellow polyethylene sheets

Summary Trials were made in an attempt to reduce the spread of the aphid-transmitted viruses, potato leaf roll virus, potato virus Y and alfalfa mosaic virus in seed potatoes. The experiments were carried out on the coastal plain of Israel, at Bet-Dagan. Seed potatoes which had been protected by ‘sticky’, yellow polyethylene sheeting showed a marked reduction in the incidence of virus-infected tubers. The percentage of potato leaf roll virus-affected tubers from protected plots, compared to that from the unprotected, control plots, was as follows: for 1974, 2 and 17.2%, for 1975, 6 and 29%, respectively. The higher infection rates for the period 1975–76 being explained by the longer aphid trapping time used which continued until 20 June in 1975, but only to 10 May in 1974. There was also a reduction in the spread of both potato virus Y and alfalfa mosaic virus.

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Zusammenfassung Es wurde untersucht, ob die Ausbreitung von Blattlaus-übertragbaren Viren-Blattrollvirus (PLRV). Alfalfa-Mosaik virus (AMV) und Kartoffel-Y-Virus (PVY)- in Pflanzkartoffełbest?nden durch den Gebrauch von Farbk?dern kontrolliert werden k?nnte. Diese Versuche beruhen auf den Ergebnissen, dass L?use von reflektiertem Licht im Bereich zwischen 500 und 700 nm stark angezogen werden (Moericke, 1969). In den Jahren 1974–1975 und 1975 1976 wurden im Frühjahr (Hauptkartoffelanbauzeit) in Bet-Dagan. Israel zwei getrennte Versuche durchgeführt. Abb. 1 zeigt zwei Parzellen 10 m × 10 m. die 30 m von einander getrennt sind. Eine ist von klebrigen gelben Poly?thylenfolien umgeben, die andere nicht- unbehandelte Kontrolle. Jeder dieser Parzellen wurde am 2. M?rz 1974 und am 5. M?rz 1975 mit irischem zertifiziertem Pflanzgut der Sorte Up-to-date bepflanzt, insgesamt 260 Knollen pro Parzelle, wobei der Abstand zwischen den Reihen 90 em und innerhalb der Reihe 35 cm betrug. Vor dem Auflaufen der Kartoffeln wurde in einem Abstand von 4 m von den Parzellenkanten bis zu einer H?he von 70 cm über dem Erdboden 4 m×0.5 m grosse Poly?thylenfolien gespannt. Diese Folien wurden mit ‘Rimi foot glue’ (R. Yewnin and M. Joffe. Technochemical factory. Tel Aviv. Israel) bedeckt, das durchsichtig ist und lange Zeit klebrig bleibt. W?hrend der Wachstumszeit wurden die Symptome beobachtet und mit Hilfe einer Wasserfalle nach Moericke, die nahe der Kartoffeln aufgestellt war, wurden die geflügelten Blattlauspopulationen gefangen, um darüber Daten zu erhalten. Die gefangenen Blattl?use wurden w?chentlich gesammelt (Zimmerman-Gries & Swirski, 1960). Vom Gesamtfang wurde nurMyzus persicae bestimmt und gez?hlt. Das Auftreten von Prim?rinfektionen durch PLRV, AMV und PVY wurde durch regelm?ssige Feldbeobachtungen erfasst. Von jeder Pflanze wurden für sp?tere Kontrollen zwei Kartoffelknollen in den für sp?tere Kontrollen zwei Kartoffelknollen in Pflanzgutgr?sse geerntet. Diese Kartoffelknollen wurden 6 Monate bei 2 3 C gelagert und dann in einem insektengeschüzten Gew?chshaus ausgepflanzt. Das Blattrollivrus wurde bestimmt, in demM. persicae von Pflanzen, in denen dieses Virus vermutet wurde, aufDatura stramonium umgesetzt wurden (Zimmerman-Gries et al., 1973). AMV, PVY und PVX wurden durch mechanische Inokulation auf Testpflanzen identifiziert. Die Abbildungen 2 und 3 zeigen die enge Verbindung zwischen der Verteilung des Gesamtfanges w?hrend der Saison und der vonMyzus persicae. Tabelle 1 zeigt die Anzahl infizierter Knollen in Prozent im ersten Nachbau von geschützten und ungeschützten Parzellen. In den Jahren 1974 und 1975 waren in den ungeschützten Parzellen viel mehr PLRV-infizierte Knollen als in den geschützten (2 und 17.2% bzw. 6 und 29%). Der h?here PLRV-Befall im Jahre 1975 kann durch die l?ngere Fangperiode fürM. persicae in diesem Jahr erkl?rt werden. Ein ?hnlicher Einfluss der klebrigen, gelben Poly?thylenfolien wurde bei der Ausbreitung von AMV (1974: 16 und 7.2%. 1975: 2.5 und 6%) beobachtet. Der Befall durch PVY war nicht so hoch wie der von Cohen & Marco (1973) festgestellte (1974: 0 und 2.4% und 1975: 1 und 3.5%). Sie fanden in 90% ihrer Pfefferproben PVY. Diese Technik, mit entsprechender Weiterentwicklung, k?nnte der Ausbreitung persistenter und nicht persistenter Viren in Pflanzkartoffelbest?nden entgegenwirken.

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Résumé La possibilité de réduire le taux de contamination du plant de pommes de terre par le virus de l'enroulement (PLRV), le virus de la mosa?que de la luzerne (AMV) et le virus Y de la pomme de terre (PVY) a été testée et la réduction a pu être possible par l'utilisation d'appats de couleur’. Ces essais ont été basés sur le fait que les pucerons sont fortement attirés par la lumière réfléchie dans la zone des 500–700 nm (Moericke, 1969). Deux expérimentations différentes ont été conduites durant le printemps (principale période de culture de la pomme de terre) des années 1974–75 et 1975–76 à Bet-Dagan en Isra?l. Deux parcelles de 10 m×10 m, séparées par une distance de 30 m, ont été retenues comme l'indique la figure 1. L'une est entourée avec des baches en polyéthylène jaune qui sont collantes, l'autre n'est pas entourée et sert de témoin non traité. Chacune de ces parcelles a été plantée avec des semences certifiées en provenance d'Irlande de la variété Up-to-Date le 2 mars 1974 et le 5 mars 1975. 260 tubercules ont été plantés dans chaque parcelle à des distances de 90 cm×35 cm. A une distance de 4 m de chaque c?té, et avant la levée des pommes de terre, une bache de polyéthylène jaune de 4 m ×0.5 m a été déployée à une hauteur de 0.7 m au-dessus du sol. Ces baches ont été recouvertes de ‘glue Rimi-foot’ (R. Yewmin et M. Joffe, usine technochimique. Tel Aviv, Isra?l) qui est transparente et qui reste collante assez longtemps. Les sympt?mes ont été observés pendant la période de croissance et un échantillonnage de la population aphide ailée a été réalisé au moyen de piège à eau du type Moericke, placé près des pommes de terre afin d'obtenir des données sur la population de pucerons ailés. Les pucerons piégés ont été collectés chaque semaine (Zimmerman-Gries & Swirski, 1960). Sur le total d'ailés recueillis, il n'y a eu queMyzus persicae d'identifier et de dénombrer. L'incidence de l'infection en cours de saison par le PLRV, AMV et PVY a été déterminée par des observations au champ à intervalles réguliers. Au moment de la récolte, il a été prélevé 2 tubercules par pied pour le test de préculture. Ces tubercules ont été conservés à 2–3 C pendant 6 mois: la mise en culture a eu lieu en l'absence de tout insecte. Le virus de l'enroulement a été identifié après acquisition parM. persicae sur des plantes suspectées être contaminées et après transmission àDatura stramonium (Zimmerman-Gries et al., 1973). AMV, PVY et PVX ont été identifiés par inoculation mécanique à des plantes tests. Peu de plantes infectées en cours de saison ont été observées. L'étroite correspondance entre la distribution saisonnière pour l'ensemble des pucerons recueillis et pourM. persicae est indiquée par les figures 2 et 3. Le pourcentage de tubercules-fils contaminés par les virus pour les parcelles protégées et non protégées est résumé dans le tableau 1, II y a eu plus de tubercules contaminés par le PLRV dans les parcelles non protégées que dans les parcelles protégées pour les deux années 1974 et 1975 (2 et 17.2%, 6 et 29% respectivement). Le pourcentage plus élevé du PLRV en 1975 peut être expliqué par la période de capture deM. persicae, plus longue cette année. Une influence similaire des baches de polyéthylène jaune qui sont collantes a été observée sur la dissémination du AMV (1974: 16 et 7.2%. 1975: 2.5 et 6%). L'incidence du PVY (1974: 0 et 2.4% et 1975: 1 et 3.5%) n'a pas été aussi grande que celle observée par Cohen & Marco (1973). Ces auteurs ont trouvé 90% de PVY dans leurs échantillons de poivre. Cette technique, avec davantage de données, peut être efficace pour lutter contre la dissémination des virus persistants et non persistants dans les parcelles de plants de pommes de terre.

     

Jemseg: A new,early high-yielding potato variety with high resistance to virus Y and immune to virus X

Jemseg is an early sizing variety of early maturity. It has outyielded the variety Warba for total and marketable yield when dug at 80 days from planting. It has moderate resistance to common scab, is immune to virus X and has high resistance to virus Y, plus resistance to virus S. Jemseg was originated at Fredericton, New Brunswick, and is a product of the potato breeding program of Agriculture Canada. The variety has been under test in New Brunswick for 10 years as seedling F67072. It has also been tested extensively in the Maritime Provinces and throughout Canada through the facilities of regional and national evaluation trials. Jemseg was selected from a progeny of a cross between the variety Sable and a Fredericton seedling F55069. Sable is an early variety developed at Fredericton. F55069 is a Fredericton seedling bred for X immunity and scab resistance. Jemseg was first grown in the field in 1967. The pedigree follows: