Field assessment of the relative importance of different aphid species in the transmission of potato virus Y

Summary Flying aphids were trapped throughout the summer on a vertical net downwind of a plot of PVY-infected potato plants. Of 6769 individuals caught, 165 transmitted PVY to tobacco test seedlings. Of 119 species or species groups caught, 20 were found to be vectors of which nine had not been recorded previously.Brachycaudus helichrysi, Myzus persicae, Phorodon humuli andAphis species accounted for 90% of transmissions andB. helichrysi alone for 52% of transmissions. The prospects of using this information to assess the amount of virus spread in a potato crop and of forecasting the timing and abundance of the main vectors are discussed.

---

Zusammenfassung Im Abwind einer Parzelle mit PVY-infizierten Kartoffelpflanzen (7% PVY^O, 4% PVY^N, 89% beide) wurden fliegende Blattl?use in zwei vertikalen Netzen (4,4 m × 1,4 m mit hexagonalen L?chern mit 1,5 mm Durchmesser) gefangen und anschliessend auf Tabaks?mlinge überführt, um zu prüfen, ob sie PVY übertragen. Die Blattl?use wurden vom 8. Juni bis zum 8. August 1984 normalerweise an einem Tag pro Woche von 10 bis 17 Uhr gefangen. Im Laufe von 12 Fangtagen wurden 6769 sachte 52% der übertragungen bei nur 15% der totalen Fangzahl (Tab. 3).B. helichrysi mitMyzus persicae, Phorodon humuli und Species des GenusAphis ergaben sich als 90% der übertragenden Individuen bei nur 32% der gefangenen Proben. Acht Prozent der gefangenenB. helichrysi waren übertr?ger, dagegen nur 4,7% vonM. persicae. B. helichrysi k?nnte als Vektor besonders wichtig sein, weil sie in der Vegetationszeit Blattl?use von 119 Species oder Speciesgruppen gefangen, von denen 165 (2,44%) Tabak mit PVY inokulierten (Tab. 1). 133 Blattl?use übertrugen PVY^O und 32 übertrugen PVY^N (und m?glicherweise auch PVY^O). 20 Species oder Speciesgruppen waren Vektoren, von denen 9 (Cryptomyzus ballotae, Hyperomyzus lactucae, Metopolophium festucae, Myzus ligustri, M. myosotidis, Myzaphis rosarum, Sitobion avenae, S. fragariae undUroleucon spp.) erstmalig beschriebene Vektoren sind.Brachycaudus helichrysi verurfrüh auftritt (Tab. 2), wenn die Pflanzen am anf?lligsten sind und die Virus-Translokation zu den Knollen am schnellsten stattfindet. Die Aussichten zum Gebrauch dieser Information zur Absch?tzung des Aufbaues von Virusbefall im Bestand und die Aussichten für eine Vorhersage der Menge der wichtigsten Vektoren werden diskutiert. Es ist dringend erforderlich, die Biologie vonB. helichrysi zu untersuchen.

---

Résumé Deux filets verticaux (4,40 m × 1,40 m à mailles héxagonales de 1,5 mm de diamètre) sont placés face au vent pour la capture des pucerons dans une parcelle de plants de pommes de terre contaminés par PVY (7% PVY^O, 4% PVY^N, 89% par les deux) puis les pucerons sont transferrés sur des plantules de tabac en milieu clos pour tester la transmission de PVY. Les captures de pucerons ont eu lieu du 8 juin au 8 ao?t 1984, en général à raison d'un journée par semaine, de 10 heures à 17 heures. Pendant les 12 premiers jours, 6769 pucerons de 119 espèces ou groupes d'espèces ont été capturés, les plantules de tabac ayant été inoculées par PVY avec 165 pucerons (2,44%) (tabl. 1). 133 pucerons étaient vecteurs de PVY^O et 32 de PVY^N (et probablement PVY^O). 20 espèces ou groupes d'espèces étaient des vecteurs dont 9 récemment enregistrés (Cryptomyzus ballotae, Hyperomyzus lactucae, Metopolophium festucae, Myzus ligustri, M. myosotidis, Myzaphis rosarum, Sitobion avenae, S. fragariae etUroleucon spp.).Brachycaudus helichrysi représentait 52% des transmissions mais seulement 15% du total capturé (tabl. 3).B. helichrysi, Myzus persicae, Phorodon humuli et les espèces du gèneAphis représentaient 90% des transmissions et 32% des captures seulement. 8,0% deB. helichrysi capturé a transmis le virus contre, 4,7% pourM. persicae. B. helichrysi peut être particulièrement important comme vecteur dans la mesure ou il appara?t t?t en saison (tabl. 2) lorsque les plantes sont très sensibles et la translocation di virus aux tubercules la plus rapide. Les perspectives à partir de cette connaissance sont discutées en vue d'analyser l'évolution du virus dans une culture et les prévisions de l'abondance des plus importants vecteurs. Une plus grande connaissance de la biologie deB. helichrysi devient urgente.

     

The infection pressure of potato virus Yo and the occurrence of winged aphids in potato fields in Sweden

Summary Water-filled yellow trays sited in a potato field were used to catch different species of winged aphids. The catches, enumerated weekly, were compared with the spread of potato virus Y^o (PVY^o), detected by bait plants of tobacco and potato, during the growing season for four years. The first detection of PVY^o, at about the same time as the first catch of winged aphids, varied from the middle of June to the middle of July in different years. In three of the four years,Rhopalosiphum padi was the dominant aphid in the beginning of the growing season and, presumably, it was responsible for the early spread of PVY^o in those years.Aphis spp. andMyzus persicae generally appeared later in the season and wingless aphids on the potato leaves were not common before the middle of July.

---

Zusammenfassung Der Infektionsdruck durch das Kartoffel-Y^o-Virus (PVY^o) und das Auftreten geflügelter Blattl?use verschiedener Arten in Kartoffelfeldern wurde in den vier Jahren von 1978 bis 1981 untersucht (Tab. 1). Der Infektionsdruck wurde durch junge K?derpflanzen in Form von Tabak und Kartoffeln (Sorten Bintje und King Edward), welche w?chentlich der Virusinfektion im Feld ausgesetzt waren, gemessen. Die geflügelten Blattl?use wurden in gelben Wasserschalen (YWT) gefangen, ungeflügelte Blattl?use wurden an 60 zuf?llig ausgew?hlten Kartoffelbl?ttern ausgez?hlt. Die erste Entdeckung von PVY^o und der erste Fang geflügelter Blattl?use koinzidierten; dies erfolgte in den verschiedenen Jahren zu unterschiedlichen Zeiten von Mitte Juni bis Mitte Juli (Abb. 1).Rhopalosiphum padi war die dominierende Blattlaus am Anfang der Wachstumsperiode in drei von vier Jahren, in denen es vermutlich Ursache für die frühe Ausbreitung von PVY^o war.Aphis spp. undMyzus persicae erschienen in der Jahreszeit generell erst sp?ter. Ungeflügelte Blattl?use auf Kartoffelbl?ttern erschienen bis zur Mitte des Jahres nur selten.

---

Résumé On étudie la pression d'infection du virus Y^o de la pomme de terre (PVY^o) en relation avec la présence dans un champ de pomme de terre de pucerons ailés de plusieurs espèces, dans le cadre d'un essai conduit durant 4 années entre 1978 et 1981 (tableau 1). La pression d'infection est déterminée au moyen de jeunes plantes de tabac et de pomme de terre (variétés King Edward et Bintje), qui sont exposés chaque semaine dans le champ à l'infection virale. Les pucerons ailés sont capturés dans un piège à bac jaune, et les pucerons aptères sont comptés directement sur 60 feuilles de pommes de terre, choisies au hasard. La première détection du PVY^o et la première capture de pucerons ailés co?ncident, ce qui a été observé à différentes époques de plusieurs années, de la mi-juin à la mi-juillet (fig. 1).Rhopalosiphum padi a été le puceron le plus abondant au commencement de la période de croissance, dans trois des quatre années où il fut présumé responsable de l'extension précoce du PVY^o.Aphis spp. etMyzus persicae apparaissent généralement plus tard dans la saison. Les pucerons aptères sur les feuilles de pomme de terre sont peu fréquents avant la mi-juillet.

     

Biological factors influencing the transmission of potato leafroll virus by different aphid species

Summary Macrosiphum euphorbiae, collected in the field from potato plants infected with potato leafroll virus (PLRV), transmitted the virus to fewer potato plants in a field trial than did laboratory-rearedMyzus persicae. In the laboratory,M. persicae was the only efficient vector of PLRV fromPhysalis floridana seedlings, potato sprouts or excised leaves toP. floridana. Two clones ofM. euphorbiae and one clone ofAulacorthum solani transmitted PLRV from infected potato plants toNicotiana clevelandii as effeciently asM. persicae but a clone ofAphis gossypii was an inefficient PLRV vector. An isolate of PLRV, whichM. persicae transmitted inefficiently from potato toN. clevelandii, was also transmitted inefficiently byM. euphorbiae andA. solani.     

Effects of glandular foliar hairs on the spread of potato virus Y

Summary Sticky glandular hairs on the foliage of the wild potatoSolanum berthaultii hindered the departure of wingedMyzus persicae andBrachycaudus helichrysi. The presence of sticky hairs also decreased multiplication ofM. persicae, lessened probing and lessened acquisition of potato virus Y during 5 min access periods. It is suggested that if the glandular hairs were bred into potato cultivars, these features would help restrict the spread of aphidborne viruses in crops.

---

Zusammenfassung Wie bereits früher gezeigt wurde, schützen klebrige Drüsenhaare auf den Bl?ttern der WildkartoffelSolanum berthaultii gegen verschiedene Kartoffelsch?dlinge einschliesslich der L?use; solche Haare gibt es in britischen Kartoffelsorten nicht. Ein Haartyp produziert ein klebriges Sekret an seiner Spitze, dieses Sekret kann mit ?thanol abgewaschen werden und eine st?ndige Berieselung mit Wasser verhindert eine Phytotoxizit?t. Ein zweiter Haartyp mit einer zellul?ren viergliedrigen Spitze wird durch das Waschen nicht beeinflusst. Drei Tage nach dem Aufsetzen von geflügeltenMyzus persicae oder geflügeltenBrachycaudus helichrysi (einem Vektor des Y-Virus der Kartoffel (PVY), der aber Kartoffeln nicht bef?llt) auf Planzen vonS. berthaultii oder von King Edward, blieben mehr als 85% auf mit Wasser berieseltenS. berthaultii, 45% auf mit ?thanol und Wasser gewaschenemS. berthaultii und nur 15–20% auf King Edward, unabh?ngig von der Behandlung (Abb. 1). Viele L?use, die aufS. berthaultii blieben, wurden gefangen und einige hatten durch das klebrige Sekret der Drüsenhaare verschmierte Mundpartien (Abb. 2).M. persicae nahm PVY h?ufiger von mit Wasser und ?thanol gewaschenen infizierten Bl?ttern vonS. berthaultii auf als von allein mit Wasser gewaschenen. Damit verbunden waren auch seltenere Probeeinstiche der L?use in mit Wasser gewaschene Bl?tter, aber h?ufige in Bl?tter deren Haare von dem klebrigen Sekret durch Alkoholwaschungen befreit waren. Diese im Gew?chshaus gewonnenen Ergebnisse zeigen, dass die Züchtung von Kartoffelsorten mit Drüsenhaaren, die vonS. berthaultii abstammen, helfen k?nnte, die Verbreitung der durch L?use übertragbaren Viren in Kartoffelbest?nden einzuschr?nken.

---

Résumé Des poils foliaires glandulaires de la pomme de terre sauvageSolanum berthaultii ont déjà été observés comme protégeant de nombreaux ennemis de la pomme de terre, y compris les aphides. De tels poils ne sont pas connus sur les variétés britanniques. Un type de poil produit un exudat gluant à son extrémité. Ces exudats peuvent être lessivés par l'éthanol, dont on prévient la phytotoxicité par un rin?age immédiat à l'eau. Un second type de poil à extrémité cellulaire tétralobée n'est pas affecté par un tel lessivage. Trois jours après l'installation d'ailés deMyzus persicae on d'ailés deBrachycaudus helichrysi (un vecteur du virus Y de la pomme de terre (PVY) mais qui ne colonise pas la pomme de terre) sur les plants deS. berthaultii ou King Edward, 85% environ demeurent surS. berthaultii rincée avec de l'eau, 45% restent surS. berthaultii la vée à l'éthanol et à l'eau, et seulement 15–20% se maintiennent sur King Edward, quel que soit le traitement (fig. 1). La plupart des aphides restant surS. berthaultii sont piégés, et certains ont leurs pièces buccales engluées par l'exudat des poils glandulaires (fig. 2).M. persicae se multiplie plus lentement surS. berthaultii lavé à l'eau que surS. berthaultii lavé à l'éthanol.M. persicae acquiert le PVY plus fréquemment à partir des feuilles infectées deS. berthaultii lavées à l'éthanol et à l'eau que sur des feuilles seulement lavées à l'eau. Conjointement, les aphides explorent rarement les feuilles lavées à l'eau, mais visitent volontiers les feuilles dont les poils sont dépourvus de l'exudat gluant par lavage à l'éthanol. Ces résultats en serre suggèrent que les variétés de pomme de terre avec des poils glandulaires provenant de croisements deS. berthaultii pourraient aider à réduire l'extension de virus transmis par les pucerons dans les cultures de pomme de terre.

     

Acquisition of potato leafroll virus byMyzus persicae from secondarily-infected potato plants of different genotypes

Summary The acquisition of potato leafroll virus (PLRV) byMyzus persicae nymphs from the top leaves of potato plants was studied throughout a growing season in relation to the antigen titre in those leaves and the feeding behaviour of the aphid. Secondarily-infected plants of eight potato genotypes with different levels of field resistance served as virus sources. Early in the growing season, plants were efficient sources for virus acquisition. The amount of viral antigen detected inM. persicae nymphs fed on the top leaves was strongly correlated with the titres of viral antigen in these leaves. Virus acquisition from the top leaves of older potato plants was markedly impaired and could not be correlated with their virus titre. With increasing age of the potato plants and the development of virus symptoms, the virus titre in the leaves declined and the initial weak correlation between the virus titre and field resistance ratings disappeared. Thus, screening secondarily-infected potato plants for field resistance to PLRV based on the concentration of viral antigen in leaves or in aphids fed on them should be avoided later in the growing season. The feeding rate ofM. persicae, measured by the number of honeydew droplets excreted, did not account for the reduced uptake of virus from older plants since it was not influenced by the age of the plant. Throughout the growing season, the feeding rate ofM. persicae nymphs on PLRV-infected plants was higher on genotypes with low levels of field resistance to PLRV than on genotypes with high ones.     

The efficiency of the bulb and potato aphidRhopalosiphoninus latysiphon (Davidson) as a vector of potato virus V

Summary Experiments to test the ability ofRhopalosiphoninus latysiphon to transmit potato virus V showed a transmission rate of 16 per cent after only two weeks; this was maintained for a further two weeks, beyond which time the rate rose rapidly. A comparison of the mode of inoculation of PVV byR. latysiphon andMyzus persicae suggested that the mechanism may be similar for both species.     

Production of seed potatoes in Cyprus: the effects of roguing and planting date on the spread of potato leaf roll virus,tuber yield,and infestation by potato tuber moth

Summary Field experiments during 1984–6 tested the effects of planting date on the development of aphid infestations and the spread of potato leaf roll virus (PLRV) in rogued or unrogued plots of potatoes, cv. Spunta. Plantings were made each month from December to April, the customary time for planting being February. Aphid infestation in early-planted plots was severe throughout the growing season; plots planted in February were also severely infested early in the growing season but the populations later gradually declined to undetectable levels. Nevertheless, the incidence of PLRV in the latter plots was as high as in those planted in December-January. Late-planted crops escaped aphid infestation and PLRV infection, either in part (March planting) or completely (April planting). Such crops, however, were uneconomical due to poor yields and heavy losses from potato tuber moth infestation. Roguing significantly reduced the spread of PLRV in all years but its interaction with planting date was insignificant.     

Environmental factors influencing aphid transmission of potato virus Y and potato leafroll virus

Summary The effect of temperature, relative humidity (RH) and light on aphid transmission of potato virus Y (PVY) and potato leafroll virus (PLRV) was studied using as vectorsMyzus persicae Sulz. andAphis gossypii Glov. Host susceptibility was enhanced by 48 h pre-inoculation exposure at 25°C and by 48 h post-inoculation exposure to 30°C. High RH (80%) in both pre- or postinoculation phases enhanced host susceptibility. Continuous fluorescent light (4000 lux) did not alter the rate of transmission of either virus. High RH (80–90%) and high temperature (25–30°C), when combined, increased virus transmission by 30–35%. Transmission rates were reduced by nearly 50% if RH was maintained at 50% in either of the two phases even if the temperature was 25 or 30°C. Both viruses were acquired by aphids earlier (13–20 days after inoculation) when the source plants were incubated at 25 or 30°C. Most virus was transmitted from plants inoculated with PVY 13 to 16 days and with PLRV 15 to 20 days previously. Transmission rates of PVY were enumerated from symptom expression on test plants and by Enzyme Linked Immunosorbent Assay (ELISA) whereas those of PLRV were enumerated from symptom expression alone.     

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.     

Diploid genotype DW.84-1457, highly resistant to potato leafroll virus (PLRV)

Summary The diploid clone DW.84-1457 which has outstanding resistance to potato leafroll virus (PLRV), has been selected at the Mlochów Centre of the Institute for Potato Research. It has in its pedigree PLRV-resistant clones from the Max Planck Institute nos. MPI 44.1016/10, MPI 44.335/130 and MPI 49.540/2. Its behaviour in the field and response to aphid inoculation indicate high resistance to infection, and the low concentration of the virus in graft-inoculated plants indicates high resistance to multiplication. This combination within one genotype of two aspects of resistance is not connected with hypersensitivity, and is heritable. Clone DW.84-1457 has other desirable characters such as extreme resistance to potato virus X (PVX), high resistance to potato virus M (PVM) and good table and processing quality. It is being utilized in the development of parental lines, both at the diploid and tetraploid level.     

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.     

Transmission of potato virus Y by cereal aphids

Summary The cereal aphidRhopalosiphum padi transmitted PVY^O and PVY^N from and to both tobacco and potato. However, it transmitted much less frequently thanMyzus persicae, even when aphids making single probes were compared.R. padi andM. persicae retained PVY for a similar duration. Both alatae and apterae ofR. padi transmitted infrequently, as also did progenies of individual aphids that had transmitted PVY.Metopolophium dirhodum also transmitted PVY infequently butSitobion avenae did not transmit.

---

Zusammenfassung In Laborversuchen übertrugen ca, 1% der Getreideblattl?useRhopalosiphum padi undMetopolophium dirhodum, nicht jedochSitobion avenae das Kartoffel-Y-Virus (PVY). 65% vonMyzus persicae übertrugen PVY.R. padi übertrugauch dann weniger h?ufig alsM. persicae, wenn die Aphiden bei Einzelentnahmen untersucht wurden.R. padi übertrug PVY^O und PVY^N von und auf die Tabaksorte White Burley und die Kartoffelsorte King Edward. Zwei oder zehn Minuten Einwirkung waren optimal fürM. persicae, um PVY zu erlangen, w?hrendR. padi PVY h?ufiger nach l?ngeren Entwirkungszeiten übertrug (Tabelle 1).R. padi undM. persicae beinhalteten PVY für eine ?hnliche Zeitdauer (Tabelle 2). Sowohl alatae als auch apterae vonR. padi übertrugen unregelm?ssig, ebenso Nachkommen von individuellen Aphiden, welche PVY übertragen hatten.

---

Résumé En tests de laboratoire, environ 1% des pucerons des céréalesRhopalosiphum padi etMetopolophium dirhodum, aucun deSitobion avenae et environ 65% deMyzus persicae transmettent PVY.R. padi transmet également moins fréquemment queM. persicae lorsque les pucerons sont mis en comparaison par piq?re unique.R. padi acquiert PVY^O et PVY^N à partir des variétés de tabac White Burley et de pomme de terre King Edward et les transmet à ces deux mêmes variétés. Deux ou 10 minutes d'acquisition sont optimum pour queM. persicae acquiert PVY tandis queR. padi transmet PVY plus fréquemment après une plus longue période d'acquisition (tableau 1).R. padi etM. persicae conservent PVY dans les mêmes délais (tableau 2). Les ailés et les aptères deR. padi transmettent rarement PVY comme les descendants de pucerons ayant transmis PVY.

     

Extreme resistance to infection by potato virus X in genotypes of wild tuber-bearingSolanum species

Summary Clones derived from thirty-one different accessions (nineteen of Argentine origin) belonging to eightSolanum species were screened for resistance to infection by potato virus X strain cp (PVX cp) by mechanical inoculation of plantlets that had been micropropagated in vitro. Estimates of PVX multiplication obtained by enzyme linked immunosorbent assay and slot blot nucleic acid hybridization allowed the identification of resistant clones derived from five accessions belonging toS. commersonii S. oplocense, S. sparsipilum andS. tuberosum andigena. Resistant genotypes supported PVX concentrations 5 to 15 times smaller than did the susceptible control cultivar Spunta. Graft inoculation test confirmed the presence of extreme resistance similar to that conferred by the ‘immunity’ gene X¹ (also called RX_act).     

Potato leafroll virus distribution in potato meristem tips and production of virus-free plants

Summary Uridine-H³ was incorporated into meristem tips of both healthy and PLRV-infected potato plants, of the cultivars, Majestic and Primura. Autoradiograms of tips pretreated with actinomycin D showed that 13 of 14 and 11 of 14 respectively, were virus free in the dome and first 4 leaf primordia, 1 and 3 were infected in the 4th leaf primordium, and 1 of Primura also in its 3rd primordium. The highest plantlet yield from cultures in vitro of meristem tips that included 4 leaf primordia (7 to 9 plantlets per meristem), was obtained by growing them in sequence on 3 sequential media, each based on Murashige and Skoog basic medium complemented with various hormones. The 2nd medium, containing benzylaminopurine (0.5 mg/l) and gibberellic acid (0.5 mg/l), elicited callus and the subsequent formation of adventitious buds. Of the plantlets of the cvs Vivaks, Primura and Majestic, 88, 91 and 100 %, respectively, were PLRV-free. Propagation in vitro, by the single-node cutting technique and tuberlet production, were successful.     

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.

---

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.

---

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.

---

---

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

---

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

Host genes and transgenes that confer resistance to a Scottish isolate of potato leafroll virus are also effective against a Peruvian isolate

Summary Potato genotypes with host gene-mediated resistance (host-MR) and coat protein-mediated transgenic resistance (CP-MR) to potato leafroll virus (PLRV), were inoculated with a Scottish and a Peruvian isolate of PLRV. The coat protein transgene had been cloned from the Scottish PLRV isolate which had also been used during the screening and selection of genotypes with host resistance. Significantly less PLRV accumulated in plants with either host-MR or CP-MR than in plants of susceptible genotypes or in non-transformed control plants, but the two forms of resistance were equally effective against both PLRV isolates.     

Influence of the duration of acquisition and inoculation feeding on the effectiveness of potato leafroll virus transmission byMyzus persicae Sulz

Summary In laboratory experiments PLRV transmission byMyzus persicae Sulz was shown to be possible even during a very brief feeding period onPhysalis floridana Rydb, in both acquisition and inoculation feeding. When the acquisition feeding time (AFT) was varied between 30 sec and 48 h the inoculation feeding time (IFT) was constant (48h) and vice versa: when the AFT was constant (48 h), the IFT was variable. The rate of infection was 2.2% following 30 sec AFT and 1.1% after 30 sec IFT. After 1 min feeding these infection rates increased to 7.9% and 1.8% respectively. The capacity for virus transmission was closely correlated with the increase in feeding time for both acquisition and inoculation feeding.     

Monitoring for MACE resistance in the tobacco-adapted form of the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) in the eastern United States

Organophosphate and carbamate insecticides exert their neurotoxic effects by inhibiting acetylcholinesterase (AChE), thereby, prolonging the action of acetylcholine at cholinergic synapses, resulting in neuronal hyperexcitation. Mutations at the AChE target site confer modified acetylcholinesterase (MACE) phenotypes. Target-site insensitivity of AChE was characterized in field-collected, tobacco-adapted forms of the green peach aphid, Myzus persicae (Sulzer), from nine different states in the eastern United States from 2004 to 2007. The specific activity of the AChE among the 65 aphid colonies screened by Ellman's assay ranged from 0.017–0.259 U/min/mg protein. Eight colonies, with a wide range of specific activities were chosen to study the inhibition of AChE in the presence of two carbamate insecticides, methomyl and pirimicarb. IC₅₀ values for methomyl ranged from 0.35 to 2.4 μM, while six out of eight colonies had lower values that ranged from 0.16 to 0.30 μM for pirimicarb. Two colonies that were inhibited by methomyl had very high IC₅₀ values for pirimicarb, 40.4 and 98.6 μM respectively. The target-site insensitivity in these two colonies that are resistant to pirimicarb could be due to an ace2 gene mutation. This is the first instance where MACE phenotypes in M. persicae from the United States were studied and confirmed. The results indicate that the possible insensitivity due to MACE resistance in some colonies may render selected carbamate insecticides ineffective. Concerns of MACE resistance in managing the tobacco-adapted form of the green peach aphid on tobacco in the United States are discussed.     

Characterization of Solanum chomatophilum resistance to 2 aphid potato pests, Macrosiphum euphorbiae (Thomas) and Myzus persicae (Sulzer)

The aphids Macrosiphum euphorbiae (Thomas) and Myzus persicae (Sulzer) (Hemiptera: Aphididae) are responsible for yield reduction in potato (Solanum tuberosum) production by direct phloem feeding and by spreading viruses. Breeding resistant traits from Solanum chomatophilum into the potato germplasm provides alternative means to control aphid infestations. Integrated pest management strategy, using plant resistance, benefits from the characterization of the resistance and of its impact on aphid biology. Our objective was to characterize the resistance of S. chomatophilum by assessing the effects of accessions, plant parts on aphid performance, and by assessing the impact of the resistance factors on different aphid developmental stages and on alate morph production. Detailed aphid performance was obtained by measuring fecundity, survival, percentage of nymphs that reached adult moult, and population growth using whole plant and clip cage experimental designs. Accession and plant physiological age, but not aphid developmental stage, influenced all life-history parameters, except for alate morph production which was not induced on the resistant accessions. Plant part influence was independent of plant species and accession. Both experimental designs resulted in congruent resistance levels at the accession level for each of the two aphid species, supporting the use of any of them in S. chomatophilum resistance screening. PI243340 was resistant to both aphid species, while PI365324 and PI310990 were also resistant to M. euphorbiae and M. persicae, respectively.     

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.