Acquisition of potato virus YN by Myzus persicae from primarily infected ‘Bintje’ potato plants

When ‘Bintje’ potato plants were inoculated mechanically with potato virus Y^N (PVY^N),Myzus persicae acquired PVY^N from both the inoculated and non-inoculated leaves about one week earlier than when plants were inoculated byM. persicae. Only when young plants of about four weeks after planting were inoculated byM. persicae, this aphid acquired PVY^N from the non-inoculated top leaves within a fortnight. When plants later than four weeks after planting were inoculated byM. persicae it generally took at least four weeks for this aphid to acquire PVY^N from non-inoculated top and other leaves of such plants. A number of leaves situated on the potato stems near to the inoculated ones did not serve as a PVY^N-source forM. persicae within the experimental period of 38 days. The results indicate that it is possible that in seed potato growing areas primarily infected PVY^N-infected plants, not yet showing symptoms, can act as virus sources for further spread. This is especially true in the beginning of the season.     

Determination of the infection pressure of potato virus YN

In 1976 consecutive series of plants ofNicotiana tabacum ‘White Burley’ replaced weekly, were used as bait plants to determine the infection pressure of potato virus Y^N (PVY^N) in a crop of ware potatoes in the centre of the Netherlands. The first PVY^N-infected tobacco plants were found mid May. The course of infection of the tobacco plants was not correlated with the flight ofMyzus persicae, which started towards the end of June. Aphid species other thanMyzus persicae presumably are responsible for the infection observed early.Rhopalosiphum padi andAcyrthosiphon pisum flew much earlier thanMyzus persicae and are vectors of PVY^N.     

Infection pressure of potato virus YN

Potato virus Y^N (PVY^N) infection was determined by the tobacco test in Swifterbant (Eastern Flevoland). In plots with beet, wheat and seed potatoes the infection exhibited an identical course. No differences were found either between PVY^N infection in the border and that in the middle of a field planted with ware potatoes, although infection pressure was clearly higher here than in the plot with seed potatoes. A barrier crop of 10 rows of wheat did not decrease the infection pressure of the virus.From August onwards, the spread of PVY^N in Lienden (Betuwe) was followed. Here virus transmission was found continuously, even until mid-November.Potato volunteers outside as well as in potato fields are serious infection sources. In 1976 and in 1977 virus spread was detected before the flight ofMyzus persicae, as determined with yellow Moericke traps. Infection pressure can be measured more efficiently by the tobacco test than by aphid trapping. The effect of rogueing at the time of virus spread should be reconsidered.If infection pressures in different areas or successive years are to be compared, the tobacco test should be standardized. A proposal to this effect is made.Samenvatting In Swifterbant (Oostelijk Flevoland) werd de infectie met het aardappel-Y^N-virus (PVY^N) bepaald met behulp van de tabakstoests. In percelen met bieten, tarwe en pootaardappelen bleek de infectie hetzelfde verloop te hebben. Tussen het infectieverloop van PVY^N in de rand en in het midden van een veld consumptieaardappelen werd eveneens geen verschil gevonden. Wel was de infectiedruk hier duidelijk hoger dan in het pootgoedperceel. Een barrier crop van 10 rijen tarwe verminderde de infectiedruk niet.De volgende conclusies kunnen worden getrokken. Aardappelopslag buiten en in aardappelvelden vormt een zeer belangrijke infectiebron. Zowel in 1976 als in 1977 vond de virusverspreiding plaats vóór de vlucht vanMyzus persicae begon, zoals deze werd bepaald met behulp van de gele Moericke vangbakken. Het effect van opzuiveren ten tijde van de virusverspreiding dient aan een nader onderzoek te worden onderworpen. De infectiedruk kan met de tabakstoets op meer directe wijze worden vastgesteld dan met bladluisvangsten mogelijk is.Wil men overgaan tot het vergelijken van de infectiedruk in verschillende gebieden of in verschillende jaren, dan dient de tabakstoets te worden gestandaardiseerd. Een voorstel hiertoe wordt gedaan.     

Effects of removal of leaves and tops on translocation of potato virus X and potato virus YN in potato plants

Removal of leaves from primarily infected plants does not stop translocation of potato virus X and potato virus Y^N from the stem to the tubers in potato plants. In some cases there is evidence that even more virus reaches the tubers. The removal of the top of a potato plant results clearly in a larger extent of infection of the tubers, as was demonstrated in experiments with both viruses. This effect proved to be greater according as the removed top was larger. Removal of leaves and tops apparently changes the physiological behaviour of potato plants in such a way that virus translocation is promoted. This means that in haulm killing, as is applied in seed potato growing, only perfect killing of the stems and leaves can result in stopping virus translocation to tubers; incomplete killing may have the opposite effect.Samenvatting In primair met aardappel-X- en aardappel-Y^N-virus besmette aardappelplanten werd het transport van virus naar de knollen voortgezet na ontbladering van de planten. In enkele gevallen bleek zelfs een zwaardere knolbesmetting op te treden. Het verwijderen van de top van aardappelplanten leidde in proeven met dezelfde virussen tot een sterkere knobesmetting dan in niet getopte planten. Dit gold des te meer naarmate de verwijderde top groter was.Het verwijderen van bladeren en top brengt een zodanige verandering in het fysiologische gedrag van de aardappelplant teweeg dat er een verhoogde mate van virustransport, dus een zwaardere knolbesmetting optreedt. Voor de teelt van pootaardappelen betekenen deze resultaten dat de loofdoding alleen het beoogde doel zal bereiken als een volledige doding van de bovengrondse plantedelen wordt bewerkstelligd.     

Aphid vectors of potato virus YN

BesideMyzus persicae a dozen other species were found to be vectors of potato virus Y^N. Eleven other species did not transmit the virus.White Burley tobacco and A6 potato are equally suitable as test plant to monitor the efficency ofRhopalosiphum padi as vector of PVY^N, but as PVY^N source tobacco is not suitable for this aphid species.Between some aphid species rather large differences exist in retention periods of PVY^N. WithR. insertum andAphis fabae transmission after a 1 h starvation period was still 50% of that without starvation. WithPhorodon humuli, M. certus andM. persicae this value was only 15, 30 and 30%, respectively.Samenvatting Van 12 bladluissoorten werd vastgesteld dat zij, evenalsMyzus persicae, vectoren van het aardappelvirus Y^N (PVY^N) zijn. Van 11 andere soorten kon dit niet worden vastgesteld. Nicotiana tabacum cv. White Burley enSolanum tuberosum cv. A6 bleken beide goed bruikbaar als toetsplant voor het vaststellen van de efficiëntie vanRhopalosiphum padi als vector van het PVY^N; voor deze bladluissoort is tabak ongeschikt als bron van PVY^N.De retentieperiode van het PVY^N lijkt bij verschillende bladluissoorten aanzienlijk te variëren. BijRhopalosiphum insertum enAphis fabae bracht één uur vasten na de acquisitie de overbrenging terug tot 50% van die welke zonder vasten werd verkregen. BijPhorodon humuli was de reductie in overbrenging na één uur vasten 85%, bijMyzus certus enM. persicae was deze 70%.     

New aphid vectors of potato virus YN

During three successive years, 1983, 1984 and 1985, winged aphids were caught alive in a potato field with a conical net and with transportable suction traps.One hundred and one aphid species or species groups were checked for their ability and efficiency in transmitting potato virus Y^N (PVY^N) from potato to potato. Seventy-eight species or species groups were found unable to transmit PVY^N, whereas twenty-three species did transmit, among them beingAphis nasturtii, Brachycaudus helichrysi, Cryptomyzus galeopsidis, Cryptomyzus ribis, Hyadaphis foeniculi, Hyalopterus pruni, Hyperomyzus lactucae, Sitobion avenae andSitobion fragariae. All species, with the exception ofA. nasturtii, are recorded the first time as vectors for PVY^N.In transmission experiments alatae caught with a conical net yielded better results than did those caught with a suction trap.Samenvatting Gedurende drie opeenvolgende jaren (1983, 1984, 1985) werden gevleugelde exemplaren van 101 bladluissoorten levend gevangen met een fuik en met verplaatsbare zuigvallen, en in een kas getoetst op hun vermogen om aardappelvirus Y^N (PVY^N) van aardappel naar aardappel over te brengen.Achtenzeventig soorten brachten het PVY^N niet over. Naast de reeds algemeen bekende vectorsoorten werden nog enkele soorten gevangen die in staat bleken PVY^N over te brengen in het laboratorium, te weten:Aphis nasturtii, Brachycaudus helichrysi, Cryptomyzus galeopsidis, Cryptomyzus ribis, Hyadaphis foeniculi, Hyalopterus pruni, Hyperomyzus lactucae, Sitobion avenae enSitobion fragariae.Met bladluizen gevangen in de fuik werden betere overdrachtsresultaten behaald dan met de bladluizen gevangen in de zuigvallen.     

Molecular characterization of potato virus YN isolates by PCR-RFLP

Based on the sequence polymorphism in the 5 terminal part of the viral genome, a range of PVY^N isolates were characterized by polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP). Three pairs of primers selected in the 5 non-translated and P1 protein region were tested. Two of them yielded PCR products of about 1Kb from all isolates tested. Restriction analysis of the PCR products gave two distinct electrophoretic patterns, whichever of the three enzymes was used. In this way, the 18 isolates were separated into two easily identifiable subgroups. All tuber necrosing isolates (PVY^NTN) were clustered in the same subgroup.     

The distribution of potato spindle tuber viroid in potato plants and tubers1

Potato spindle tuber viroid (PSTV) in potato plants was investigated by ‘return’ gel electrophoresis. The experiments were carried out under quarantine conditions in the greenhouse with primarily and secondarily infected plants. The PSTV content in different plant parts was estimated by the intensity of the viroid band in polyacrylamide gel. The results showed a decrease of viroid content from the upper to the lower parts of the plant. In both primarily and secondarily infected plants, PSTV was reliably detected in the top leaves, but less so in the lower leaves. In four out of ten secondarily infected plants, PSTV was found in the roots. In dormant tubers, the bands were more intense with samples obtained from the rose end and the heel than from those obtained from the medullary tissue. With one exception, all 64 tubers from 26 primarily infected plants were infected with PSTV.     

Mature plant resistance of potato against some virus diseases. III. Mature plant resistance against potato virus YN,indicated by decrease in ribosome-content in ageing potato plants under field conditions

The concurrence of a decrease of the concentration of ribosomes and glycoproteins in leaves of potato plants under field conditions and mature plant resistance against potato virus Y^N was studied. On four of five dates with intervals of one or two weeks plants of randomly chosen plots in the field were inoculated. During plant growth sixth, tenth and fifteenth leaves of main stems were collected at regular intervals. With the aid of cellulose columns and polyethylene glycol-containing solvents the ribosome- en glycoprotein-contents (and in one experiment also the RNA-content) of these leaves were determined. Tubers were harvested from plants, inoculated fourteen days before. Lack of typical virus symptoms on plants grown from these tubers gave information on the presence of mature plant resistance.It was concluded that in plants which had developed about 20 leaves, there was a high degree of mature plant resistance when ribosome- and glycoprotein-contents in the fifteenth leaf was less than 2 and 4 OD₂₆₀/ml/g fresh weight respectively. When higher absorbance values are measured, mature plant resistance may or may not occur depending on environmental conditions. The ribosome- and glycoprotein-contents have a remote relation to the mature plant resistance. It is suggested that ribosome- and glycoprotein-contents of the youngest fully expanded leaves give the best indication of mature plant resistance.Samenvatting In veldproeven werde het verband tussen de concentraties van ribosomen en glycoproteinen in bladeren van aardappelplanten en de ouderdomsresistentie tegen aardappel Y^N-virus (PVY^N) bestudeerd. Op vier of vijf data met tussenpozen van een of twee weken werden planten in het veld met PVY^N geïnoculeerd. Gedurende de groeiperiode van de planten werden zesde, tiende en vijftiende bladeren op vastgestelde tijden verzameld. Chromatografische analyse met behulp van cellulosekolommen en solvents die polyethyleenglycol bevatten, leidde tot de bepalingen van de ribosoom- en glycoproteïnegehalten (en in één proef ook het RNA-gehalte) in de verzamelde bladeren. De oogst van de knollen vond plaats 14 dagen na inoculatie. Het niet tot ontwikkeling komen van de typische virussymptomen bij planten, die uit deze knollen waren gegroeid, was een aanwijzing voor het optreden van de ouderdomsresistentie.Geconcludeerd wordt dat waarschijnlijk enige mate van ouderdomsresistentie tegen PVY^N in een pootaardappelgewas aanwezig is, als het ribosoom- en glycoproteïnegehalte in het vijftiende blad van hoofdstengels met ongeveer twintig bladeren, leidt tot corresponderende extinctiewaarden bij 260 nm per ml en per gram vers gewicht van respectievelijk minder dan 2 en 4. Wanneer hogere extinctiewaarden worden gevonden kan ouderdomsresistentie wel of niet in belangrijke mate voorkomen, afhankelijk van de omstandigheden waaronder het gewas is gegroeid. Gesuggereerd wordt de jongste volledig ontwikkelde bladeren te gebruiken voor het aantonen van een gelijktijdig optreden van de afname in de ribosoom- en glycoproteïnegehalten en een praktisch waarneembare mate van ouderdomsresistentie.     

Relation between concentration of potato virus YN and its availability to Myzus persicae

The ability ofMyzus persicae to transmit PVY^N from potato to tobacco is not influenced by the temperature at which aphids are reared. A positive correlation exists between the relative virus concentration of PVY^N in potato as determined by serology and A6-test, and its availability toM. persicae as indicated by transmission tests to tobacco.Samenvatting De Bokx en Piron (1977) vonden, dat de virusconcentratie van aardappelvirus Y^N (PVY^N) in Eersteling positief was gecorreleerd met de temperatuur, waarbij aardappelplanten werden geteeld. De vraag is nu of er een verband bestaat tussen de virusconcentratie in de waardplant en de verspreiding van PVY^N-virus door bladluizen (Myzus persicae). Myzus persicae gekweekt bij verschillende temperaturen (Tabel 1) werd gebruikt voor virusoverdracht uit aardappelplanten geteeld bij 22°C (=gelijke virusconcentratie), terwijl bladluizen gekweekt bij kamertemperatuur werden gebruikt voor overbrengen van PVY^N uit planten geteeld bij verschillende temperaturen (=verschillende virusconcentraties).De overdracht van PVY^N doorM. persicae, werd niet beïnvloed door de temperatuur waarbij de bladluizen werden gekweekt. Er was echter een positieve correlatie tussen de relatieve concentraties van PVY^N in aardappel, bepaald volgens de microprecipitatietoets en de A6-bladtoets, en de overdracht door bladluizen naar tabak (Fig. 1).     

Direct infection of potato tubers by the root parasite Orobanche aegyptiaca

Parasitic plants of the Orobanchaceae are known as obligate root parasites that develop haustoria that connect to roots of various host plants. This article describes, for the first time, a case where the root parasite successfully connected to potato tubers, i.e. to the swollen portion of an underground stem rather than to a root. The rhizosphere of Orobanche aegyptiaca and of its host Solanum tuberosum (potato) was carefully examined. In anatomical studies, the adventitious roots were directly connected to potato tubers. Numerous secondary haustoria, which developed along the adventitious roots in close vicinity to the potato tuber, penetrated the tuber epidermis and the perimedullary tuber parenchyma and developed xylem strands that are presumably connected to the minor xylem strands within the tuber cortex. These findings indicate that parasites of the Orobanchaceae that normally attack host roots may also parasitise underground stem tubers.     

Localization of potato leafroll virus in leaves of secondarily-infected potato plants

Potato leafroll virus (PLRV) antigen was localized by immunogold labelling in semi-thin leaf sections of secondarily-infected potato plants cv. Bintje. Viral antigen was present in all cell types of the phloem tissue. but occurred most abundantly in the companion cells. Detectable amounts of PLRV antigen were found only in the sieve elements in veins with a large number of infected companion cells. Occasionally, parenchyma cells were also found to be infected. PLRV was not exclusively limited to the phloem tissue in the infected potato plants, but was also found in mesophyll cells neighbouring minor phloem vessles. Spread of virus from cell to cell in the mesophyll was not observed. The distribution of PLRV in the potato leaf tissue has implication on its availability, for acquisition by aphids.     

Biological characterisation of various geographical isolates of potato virus Y inducing superficial necrosis on potato tubers

A range of selected PVY isolates that induce superficial necrosis on potato tubers, originating from several countries, were compared with standard strains of PVA, PVV and PVY. Biological properties (e.g., host range, aphid transmissibility and relationships based on cross-protection between virus isolates) were studied. PVY^NN isolates differ from the normal PVY^C, PVY^N and PV^O strains by their ability to infect Capsicum annuum but not Chenopodium amaranticolor and C. quinoa. All PVY^NN isolates are transmissible by Myzus persicae , without any significant differences from one standard strain. These additional data confirm that these tuber-necrosing isolates belong to PVY. However, they could be ranged in a homogeneous and distinct group inside the PVY^N group, based on the differences revealed in the host range, in addition to the specific ability naturally to induce necrosis on tubers.     

An analysis of the diphenylamine reaction in sap of healthy and leaf roll virus infected potato plants

Summary An analysis was made of a difference in colour development between saps from healthy and leaf roll virus (PLRV) infected potato plants, manifested in the diphenylamine reaction ofDische. The colour development was found to be caused by sugars. The differences in colour development were due to the sugar concentration which could be different in healthy and diseased leaves, and not to DNA in the latter. We could correlate the increases in sugar concentration with the severity of virus symptoms. The mechanical transmission of the PLRV, as suggested byBrandenburg (1962), could not be confirmed.Samenvatting Een verschil in kleur, dat tussen sap van gezonde en bladrolviruszieke aardappelplanten door de difenylmaine-reactie vanDische kan optreden, werd geanalyseerd. Het bleek dat de kleurontwikkeling werd veroorzaakt door suikers. De verschillen in kleur van de reactiemengsels waren te wijten aan het feit dat de suikerconcentratie in bladeren van zieke planten een hogere waarde kan bereiken dan in bladeren van gezonde planten en niet aan een hoger desoxyribonucleïnezuurgehalte in zieke bladeren. Er bleek een duidelijke correlatie te bestaan tussen de stijging van de suikerconcentratie en de sterkte van de bladrolsymptomen. De mechanische overdracht van het bladrolvirus, zoals die doorBrandenburg (1962) was gesuggereed, kon niet worden bevestigd.     

Molecular breeding for virus resistant potato plants

To engineer resistance against potato virus X (PVX), the viral coat protein (CP) gene has been introduced into two potato cultivars. Stable expression of the gene in transgenic clones throughout the growing season has been obtained and resulted in considerably increased virus resistance. With varying frequencies depending on the original cultivar used, true-to-type PVX resistant transgenic clones have been obtained. Since deviant light sprout characteristics were invariably associated with aberrations in plant phenotype, they can be used in procedures to early screen for deviations. Furthermore, it has been possible to unequivocally discriminate between the original untransformed and independent transgenic cultivars. Although no relation has been found between the presence, if any, of the CP of potato virus Y (PVY) or potato leafroll virus (PLRV) in CP gene transgenic potato, appreciable levels of resistance to these viruses has been obtained. This suggests that the mechanism by which a viral CP gene in the potato genome evokes resistance, differs amongst various viruses.     

Molecular breeding for virus resistant potato plants

To engineer resistance against potato virus X (PVX), the viral coat protein (CP) gene has been introduced into two potato cultivars. Stable expression of the gene in transgenic clones throughout the growing season has been obtained and resulted in considerably increased virus resistance. With varying frequencies depending on the original cultivar used, true-to-type PVX resistant transgenic clones have been obtained. Since deviant light sprout characteristics were invariably associated with aberrations in plant phenotype, they can be used in procedures to early screen for deviations. Furthermore, it has been possible to unequivocally discriminate between the original untransformed and independent transgenic cultivars. Although no relation has been found between the presence, if any, of the CP of potato virus Y (PVY) or potato leafroll virus (PLRV) in CP gene transgenic potato, appreciable levels of resistance to these viruses has been obtained. This suggests that the mechanism by which a viral CP gene in the potato genome evokes resistance, differs amongst various viruses.     

草甘膦异丙胺盐杀灭香蕉病毒病植株的研究

本研究比较了41%草甘膦异丙胺盐水剂喷雾、假茎注射和叶鞘点滴3种施用方法对香蕉病毒病病株的灭除效果。结果表明:(1)香蕉假茎注射3、5和10mL草甘膦异丙胺盐,随着注射剂量的增加,香蕉株高抑制率、叶片死亡率、植株枯死率增加,注射10mL,药后30d的植株死亡率为90.0%,显著高于其他2个处理。(2)草甘膦异丙胺盐稀释成200倍液喷雾处理香蕉,药后30d,植株枯死率达93.3%,显著高于300、400倍液处理。(3)3种使用方法比较,药后15d,喷雾法处理的叶片、植株枯死率显著高于假茎注射和叶鞘点滴法,而对株高抑制率差异不显著,药后30d,3种使用方法的灭除效果等于或高于90.0%,处理间差异不显著。考虑操作的方便,叶鞘点滴法和假茎注射法可作为防除感染病毒病香蕉植株的高效使用方法,注射和点滴剂量为10mL。     

The activity of glyphosate and aminotriazole against volunteer potato plants and their daughter tubers

In three experiments, glyphosate (1.0 kg/ha) and aminotriazole (1.5 kg/ha) killed volunteer potatoes. Glyphosate (0.5 kg/ha) gave acceptable control in the field but not in the two pot experiments; in these latter, addition of ammonium sulphate to glyphosate improved its performance. Field applications of both herbicides at the end of May were less effective than those in June and July, because not all the sprouts had emerged in May. Aminotriazole killed those daughter tubers already pre sent, whilst glyphosate affected sprout viability and hence their ability to produce new plants. The practical potential of these two herbicides for the control of volunteer potatoes is discussed. Activité du glyphosate el de l'aminotriazole contre les repousses de pommes de terre et leurs tubercules fils Dans trois expériences, le glyphosate (1,0 kg/ha) et l'aminotria-zole (1,5 kg/ha) ont tue les repousses de pommes de terre. Le glyphosate (0,5 kg/ha) a fait preuve d'une efficacité acceptable au champ mais pas dans les deux expériences en pots; dans celles-ci, I'addition de sulfate d'ammonium au glyphosate a amélioré ses performances. Les applications au champ des deux herbicides à la fin de mai ont été moins efficaces que celles effectuées en juin et juillet parce que toutes les repousses n'étaient pas sorties en mai. L'aminotriazole a tué les tubercules fils déjà présents, alors que le glyphosate a affecté leur germina tion et par suite leur capacitéà produire de nouvelles plantes. La valeur pratique de ces deux herbicides pour lutter contre les repousses de pommes de terre est discutée. Die Wirkung von Gtyphosat und Aminotriazot auf Unkraut-Kar-toffelpflanzen und deren Tochterknollen In drei Versuchen wurden durch Glyphosat (1,0 kg/ha) und durch Aminotriazol (1,5 kg/ha) Unkraut-Kartoffeln abgetotet. Glyphosat (0,5 kg/ha) ergab unter Feldbedingungen eine brauchbare Bekampfung, nicht jedoch in zwei Gefassver-suchen; in letzteren wurde die Wirkung von Glyphosat durch den Zusatz von Ammoniumsulfat verbessert. Die Feldbehan-dlung Ende Mai war bei beiden Herbiziden weniger wirksam wie im Juni und Juli, weil im Mai das Kraut noch nicht voll entwickelt war. Durch Aminotriazol wurden alle bereits vor-handenen Tochterknollen getötet, wogegen Glyphosat das Kraut schädigte und damit auch die Bildung neuer Pflanzen beeinflusste. Es werden die Möglichkeiten diskutiert, die sich durch die beiden Herbizide für die Bekämpfung von Unkraut-Kartoffeln ergeben.     

Transgenic potato plants expressing the potato virus X (PVX) coat protein gene developed resistance to the viral infection

The gene coding for potato virus X (PVX) coat protein (CP) was expressed in transgenic potato plants obtained byAgrobacterium tumefaciens transformation. One hundred independent clones were analyzed in challenge experiments for resistance to PVX infection under greenhouse conditions as a preliminary test. From this test, 16 clones with the best resistance results were selected for a small-scale field trial. Clones 54, 60, 73 and 91 demonstrated the best values of resistance to PVX in the field. Statistical analysis of the field trial showed significant differences between means of optical density obtained in ELISA from transgenic clones and non-transformed plants (P<0.05). There was correspondence between resistance to virus infection and expression of the CP gene of PVX virus in the analyzed clones. http://www.phytoparasitica.org posting Jan. 21, 2002. Corresponding author [e-mail: vivian.doreste@cigb.edu.cu].