Eradication of potato virus X from potato by ribavirin treatment of cultured potato shoot tips

Ribavirin treatment of cultured potato shoot tips was tested as a means of eradicating potato virus X (PVX) from two potato cultivars. Shoot tips were cultured on liquid medium containing 0, 1, 10 or 100μg/ml ribavirin. Cultures were evaluated periodically for viability, and scored for vigor on a relative growth scale. Developed plantlets were assayed for PVX by transmission tests toGomphrena globosa. Ribavirin treatment was phytotoxic at all tested concentrations, and lethal to all cultivars treated at 100 μg/ml. Treatment also delayed plantlet development by up to 2 months at 1 and 10 μg/ml as compared with nontreated controls. PVX assays indicated that 80 and 83% of the plantlets were free of PVX following treatment with 10 μg/ml for cultivars Russet Burbank and Red McClure, respectively. Five and 6% of the plantlets developed from the 1 μg/ml treatment were PVX-free, whereas 0 and 2% of the controls were PVX-free for the same cultivars. Six to 8 months were required to develop plants from shoot-tip cultures treated with 10 μg/ml ribavirin.     

Elimination by chemotherapy of potato virus S from potato plants grown in vitro

Summary Potato virus S was eliminated from systemically infected stem cuttings of five potato cultivars after three passages in nutrient media containing 0.003% of the synthetic riboside ribavirin (Virazole). Treatment effects could be detected after only two passages which also revealed differences in cultivar response. Treated plants transferred to ribavirin-free culture media and to soil remained PVS-free. This simple method is less time-consuming than the usual meristem (axillary) tip culture procedures combined with chemotherapy or heat treatment.     

Potato virus X eradication in cultured potato meristem tips

Summary Potato virus X (PVX) infectivity of three series of axillary potato meristem tips, each including the apical dome plus one, two and four leaflets respectively, was compared statistically with the infectivity of three series of plantlets developed from meristem tips of corresponding sizes, cultured in vitro. PVX eradication depends on the size of meristem tips. The difference between the percentage of PVX-infected plantlets and the percentage of PVX-infected meristem tips was found statistically significant when one and two leaflet meristem tips were considered. This result gives experimental evidence of an active role of meristem tips development in the virus eradication process.     

Eradication of PVS from potato clones through excision of meristems from in vitro,heat-treated shoot tips

In vitro shoot tips from PVS-infected potato breeding clones and cultivars were exposed to a constant temperature of 34 C and 8,100 lux light. Meristems were excised from heat-treated shoot tips after 3 to 7 weeks of heat therapy. Serological tests were performed on shoot tips derived from meristems excised from heat-treated shoot tips. Additional serological tests, combined with bioassays, applied to six-week-old pot-grown cuttings derived from these shoot tips, did not detect PVS in 19 out of 21 clones given heat therapy. A 90% rate of eradication was achieved.     

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.

     

Eradication of potato viruses A and S by thermotherapy and sprout tip culture

Summary Potato viruses A and S have been eradicated from varietiesJara andRajka by applying thermotherapy combined with nutrient culture of excised sprout tips.     

High yield of PVY-free potato plants from axillary bud cultures after application of lysolecithin analogues and aminoadamantane

Summary Lysolecithin analogues and aminoadamantane were tested in vitro for their antiphytoviral effect on axillary bud cultures of potato infected with potato virus Y (PVY). Ethyllecithin added to the medium (700 mg/l) gave the best therapeutic effect on axenic axillary buds that were 1.67 mm long. Applying that compound, explant size may be increased and lead to virus elimination without thermal treatment. Thus viruses can be eliminated more effectively than with conventional methods.     

Comparison of the protein in axillary bud tubers and underground stolon tubers in potato

To determine if axillary leaf bud tubers can be used to study tuber protein synthesis in potato we have compared the proteins in axillary bud tubers with those in underground stolon tubers in the variety Superior. By SDS polyacrylamide gel electrophoresis and by electrophoresis in nondenaturing polyacrylamide gels at pH 8.6, the proteins in axillary bud tubers appear to be the same as those in underground stolon tubers. The proteins also appear to be immunologically identical based on Ouchterlony double immunodiffusion test and immunoelectrophoresis.     

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.     

Some properties of potato virus S isolated from Peruvian potato varieties

Summary Potato virus S (PVS) was isolated from several Peruvian potato varieties showing different symptoms ranging from mild systemic mosaic to yellowing and bronzing of the lower leaves. The properties of PVS from the potato varietyMantaro in crude sap are as follows: thermal inactivation point between 56°C and 62°C, 6 days longevity in vitro at room temperature; and dilution end point between 10⁻⁴ and 10⁻⁵. This isolate had the unique property of giving systemic symptoms onChenopodium quinoa. Paper read at the Virology Section Meeting of the EAPR, June 1971.     

Eradication of potato wart disease from Maryland

Potato wart disease, caused bySynchytrium endobioticum (Schilb.) Perc., is a disease of quarantine significance due to the production of persistent resting spores and lack of effective chemical control measures. The disease was present in limited areas of Pennsylvania, Maryland and West Virginia in 1918–1920 and was thought to have been eradicated by 1974. A recent survey in Maryland to verify eradication in that state had revealed the presence of resting spores of the fungus in one home garden in Allegany County. A subsequent delimiting soil sample survey was conducted in and around the old quarantine area in Allegany County. None of the soil samples from 176 home gardens surveyed were positive forS. endobioticum resting spores. Bioassays with susceptible potato cultivars were conducted for five consecutive years at the site from which spores had been recovered. During three of the five years, environmental conditions did not preclude development of disease, yet no symptoms were obtained. According to the USDA APHIS guidelines for eradication of potato wart disease, the spores at the Allegany County, Maryland site are declared nonviable and Maryland is considered to be free of the potato wart pathogen.     

Detection of potato leaf roll virus and potato viruses M,S, X and Y by dot immunobinding on plain paper

Summary Potato leafroll virus and potato viruses M, S, X and Y in green leaves were detected by dot immunobinding (DIB) on plain paper and on nitrocellulose membranes. On both materials, DIB could detect the presence of very small amounts of virus, e.g. 30 pg of purified PVX. The sensitivity of the DIB test on plain paper and on nitrocellulose was compared to Double Antibody Sandwich ELISA (DAS-ELISA) by serial dilutions of infected plant sap made in healthy plant sap. Detection of potato viruses by DIB on plain paper and nitrocellulose was found to be equally sensitive whereas DAS-ELISA was 2 to 8 times more sensitive. Possible simplifications of the DIB procedure to suit the requirements of a routine method were examined. The use of the DIB method for routine testing of potato viruses is discussed.     

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.     

Potato virus X eradication from potato meristem tips held at 30°C

Summary Thermotherapy of PVX infected potato plants at 30°C followed by in vitro tip culture at 24°C was more or less successful depending on the duration of the heart treatment. Virus inactivation in meristematic tissues was much more efficient when the heat treatment was applied to mature plants rather than to meristem tips cultured in viro. By combining 30°C treatment of potato plants with 30°C tip culture. PVX eradication was not improved but the final proportion of PVX-free plantlets was increased because the tip population developed faster, giving a higher number of rooted plantlets at 30°C than at 24°C.     

Transmission of potato virus Y by aphids trapped in potato crops in southern England

Summary Harrington et al. (1986) assessed the relative efficiency with which different aphid species transmitted potato virus Y (PVY), by trapping flying aphids on a net downwind of a plot of infected potatoes and transferring the aphids to tobacco seedlings. This paper reports the extension of that work over further seasons and identifies three more vector species,Aphis sambuci, Myzus cerasi andDysaphis sp. A method for determining the proportion of those aphids caught on the net that had landed and probed in the crop is suggested. The use of such information to improve a model of virus spread is discussed.     

Spread of potato virus S

Summary An experiment withEersteling (originally freed by meristem culture from PVX and PVS) andAlpha plants has been carried out in the field to study the spread of potato virus S. It was shown that depending on virus isolate, in a crop containing approximately 10% of plants with secondary infection, the primary infection inEersteling could rise to 56–76%, whereas that percentage inAlpha plants rose to 2–28 only. From the pattern of infected plants in was concluded that under field conditions in the Netherlands potato virus S is probably transmitted by contact.     

Detection of potato virus M and potato virus S on test plants

Summary The influence of environment and virus isolate on PVM detection on eight plant species and PVS detection on six plants species was investigated.Lycopersicon chilense was the most reliable test plant for PVM andChenopodium quinoa for PVS. In both cases 12–24 days were required for the symptoms to appear. The most rapid development of PVM symptoms resulted from inoculation onPhaseolus vulgaris Red Kidney (4–8 days) and of PVS symptoms on detached leaves ofSolanum demissum Y (6–8 days). The detectability of the viruses on these test plants was, however, lower than onL. chilense andC. quinoa.

---

Zusammenfassung An 8 bzw. 6 Pflanzenarten wurde die Reaktion auf eine Inokulation mit dem Kartoffel-M-virus (PVM) bzw. dem Kartoffel-S-virus (PVS) untersucht. Die Symptome sind in Tabelle 1 beschrieben. Untersuchungen, die in 3 temperaturkonstanten R?umen (16, 22 und 28°C) durchgeführt wurden, ergaben, dass unabh?ngig von der Temperatur nach Inokulation mit PVM aufLycopersicon chilense undSolanum rostratum Symptome auftraten, nach Inokulation mit PVS aufChenopodium quinoa, L. chilense undS. rostratum (Tabelle 2). Tests, die im Winter und im Sommer mit 12 Isolaten des PVM und 8 Isolaten des PVS durchgeführt wurden, ergaben, dass sich aufL. chilense undS. rostratum für PVM und aufC. quinoa für PVS unabh?ngig von der Jahreszeit und vom Virusisolat Symptome bildeten (Tabelle 3). Die am besten geeigneten Testpflanzen warenL. chilense für PVM undC. quinoa für PVS. Insgesamt wurden 200 Versuche zu verschiedenen Zeiten des Jahres durchgeführt (Tabelle 4). Jedoch, die vielleicht am besten geeignete Testpflanze für PVM istPhaseolus vulgaris Red Kidney und für PVS sind es abgeschnittene Bl?tter vonSolanum demissum Y, da die Symptome bereits wenige Tage nach der Inokulation mit allen getesteten Virusisolaten auftreten. Die Schwierigkeit bei der Verwendung dieser Testpflanzen ergibt sich aus der sehr starken Abh?ngigkeit der Symptomausbildung von den Versuchsbedingungen.

---

Résumé La réaction au virus M et au virus S, respectivement de 8 et 6 espèces de plante, a été étudiée. Les sympt?mes qui sont apparus sur les plantestests, inoculées avec le virus M et avec le virus S, sont décrits dans le tableau 1. Des expériences conduites dans trois chambres à température contr?lée (16, 22 et 28°C) ont montré, qu'indépendamment de la température, le virus M produisait des sympt?mes surLycopersicon chilense etSolanum rostratum, et le virus S surChenopodium quinoa, L. chilense etS. rostratum (tableau 2). Des tests réalisés en hiver et en été avec 12 isolats de virus M et 8 isolats de virus S ont montré que les plantes-tests qui manifestaient chaque fois des sympt?mes, indépendamment de l'isolat utilisé, étaientL. chilense etS. rostratum pour le virus M, etC. quinoa pour le virus S (tableau 3). Deux cents tests réalisés sur la pomme de terre à différentes époques de l'année ont montré queL. chilense pour le virus M etC. quinoa pour le virus S étaient les plantes-tests les plus s?res (tableau 4). Toutefois, la plante-test la plus prometteuse est peut-être pour la détection du virus M,Phaseolus vulgaris Red Kidney; et pour la détection du virus S, les feuilles deSolanum demissum Y, car les sympt?mes étaient apparus quelques jours seulement après l'inoculation, quel que soit l'isolat testé. La difficulté d'utiliser ces plantestests réside dans le fait que le développement des sympt?mes est hautement dépendant des condition d'environnement.

     

Incidence of potato virus Y and potato leaf roll virus in autumn potatoes in Israel

Summary Random sampling of autumn grown potatoes in Israel revealed potato virus Y incidences of 2.7, 2.5 and 3% during the years 1976, 1977 and 1978, respectively, figures only slightly higher than those found in spring-planted fields (2.3% in 1976), and which agree with visual estimates by the Inspection Service. Assaying random samples for potato leaf roll virus (PLRV) by aphid transmission to test plants, detected incidences as high as 38.8, 28.9, 36.7 and 33.3% during 1976, 1977, 1978 and 1979, respectively, although only minor levels were visable, indicating symptom masking in the autumn. Most of the infection was found to be secondary; ca. 25% of the local seeds for autumn planting, grown during spring, are PLRV-infected. The effect of the high incidences of PLRV on autumn yields is not known, but they are consistently lower than spring yields of the same varieties. Contribution No 315-E, 1980 Series, The Volcani Center, Bet Dagan, Israel.