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.     

The potential for production of high quality seed potatoes in Tierra del Fuego Island, Argentina

Summary In Argentina, different areas are suitable for seed potato production: however, each has particular problems, mainly related to different pest and diseases. Tierra del Fuego Island is well isolated from traditional potato growing areas. Therefore, it was tested for its potential for seed production. The cultivars Achatt. Mailén INTA. Pampeana INTA and Spunta were grown in Río Grande, San Pablo and Ushuaia from 1991–1994. Nematode presence and aphid population dynamics were recorded. Average tuber yield ranged from 20.1–37.6 t ha⁻¹. After three years PVY and PLRV remained low (0–1% for different cultivars and locations). Moreover, seed tubers obtained were physiologically young. Long days, early frosts and strong winds may limit tuber yield in some years. The island can be considered as an ecological “safe haven” and is very suitable to obtain healthy and physiologically adequate seed potatoes.     

Occurrence of Viruses Affecting Potato Crops in Khartoum State-Sudan

The incidence of Alfalfa mosaic virus (AMV), Potato leafroll virus (PLRV), and Potato virus Y (PVY) in potato crops derived from various types of seed potatoes was assessed visually and confirmed by direct tissue blot immunoassay, over two winter growing seasons (1999/2000, 2000/2001) at three locations, Elnaiya, Elshehinab, and Shambat in Khartoum State, the main potato growing region in Sudan. Virus infection was most prevalent in 2000/2001. In general, crops grown directly from imported certified seed potatoes and from “improved seed”, produced in Sudan from imported basic seed, showed the lowest levels of PLRV and PVY compared with crops grown from Sudanese farm saved seed. For AMV, however, only crops grown directly from imported certified seed potatoes had low levels of AMV. Crop location also affected virus incidence, although this varied with year. For AMV, levels were similar at all locations in 1999/2000, but were greatest at Elnaiya in 2000/2001. For PVY, levels were greatest at Elnaiya in 1999/2000 and Shambat in 2000/2001. For PLRV, no symptoms were observed in 1999/2000 and virus levels were similar for all locations in 2000/2001. This study reports for the first time the occurrence of AMV in potatoes grown in Sudan.     

Attempts to extend seed potato production in Israel to new areas at high altitudes

Summary Attempts were made to grow seed potatoes in the Gilboa mountains and central Golan Heights both at ca 500 m altitude. The activity of winged aphids was low between May and September, the period suitable for growing seed potatoes. Potato virus X (PVX) and potato virus Y (PVY) were rare. The highest incidence of potato leaf roll (PLRV) was 17% at Gilboa and 5% at Nov (central Golan). In both areas, spindle sprout was a severe problem in progeny tubers and it was associated with a purple top syndrome, probably caused by a mycoplasma, that appeared during growth. Activity of the probable vector, the leafhopperHyalesthes obsoletus, ceases in the Golan after June. Delaying planting until the end of May or later reduced the incidence of purple top and spindle sprout to nil. Both were reduced by Temik treatment and by covering the plots with netting but not by treatments with Rogor and Croneton. All three chemicals reduced PLRV incidence. Therefore, delayed plantings and insecticides may reduce purple top, spindle sprout and PLRV. This work was partly supported by funds of BARD 339-80.     

Assessment of Possibilities of Microtuber and in vitro Plantlet Seed Multiplication in Field Conditions. Part 1: PVY,PVM and PLRV Spreading

Currently in vitro plantlets and microtubers provide the basis for pre-base production of potato seeds, from which minitubers are produced under covers – they serve later as seed material to be planted in the field. The aim of the research was to determine the possibility for multiplication of material produced in vitro directly in field conditions. The research assessed PVY, PVM and PLRV infection of potato tubers derived from plants grown directly from in vitro plantlets, microtubers, minitubers and traditional seed potatoes planted in the field at different times. Moreover, testing in laboratory conditions, the susceptibility of these plants to virus infection was determined for the case of artificial inoculation of Myzus persicae and Aphis nasturtii. It was found that the infection of tubers derived from in vitro plantlets and microtubers was greater than that of seed potatoes and minitubers. Yet it seems that the reason for their higher infection level resulted not from the plant’s sensitivity or its greater attractiveness to aphids but from a largely unknown cause. Earlier planting of microtubers and in vitro plantlets in the field in case of the more resistant cultivar and certainly later in relation to the main time of planting had an impact on limiting the PVY and PVM infection of potato tubers. Hence multiplication of microtubers and in vitro plantlets in field conditions could be very economical using cultivars which are relatively resistant to viruses. However, adopting a later than usual planting period (end of June) and applying an additional protective cover (such as non-woven agricultural fabric) in the first period of a plant’s growth, promotes multiplication of microtubers and in vitro plantlets in field conditions for cultivars with low resistance levels.     

Volunteer potatoes as a source of potato leafroll virus and potato virus X

Volunteer potatoes were investigated as infection sources for potato leafroll virus (PLRV) and potato virus X (PVX) in a high elevation seed potato growing area of eastern Idaho. Population densities ofMyzus persicae were assessed. Percentage of PLRV and PVX infection of the volunteers and seed potato crops was determined, as well as density of volunteers and certain parameters of volunteer growth and reproduction. Volunteers apparently harbored no more PLRV than the potato crop from which they originated. But they were found to be an important reservoir of PVX with the infection increasing as much as 12.43% in one year. No aphids capable of transmitting PLRV were found although one species that can transmit potato virus Y was recorded. The mean density of volunteers varied from 0 to 84,880 stems/ha. The number of tubers remaining in the field after harvest and winter weather conditions appeared to be the only factors affecting volunteer density. Volunteer plants arising from seed pieces at an average depth of 6.1 cm were found to set an average of 2.1 new tubers per plant at an average depth of 4.0 cm. These results suggest that volunteer potatoes are a significant source of PVX infection in subsequent seed potato crops.     

The infection pressure of potato leafroll virus and potato virus Y in relation to aphid populations in Cyprus

Summary The infection pressure of two viruses, potato leafroll (PLRV) and potato virus Y (PVY), both common in seed potatoes grown in Cyprus, was determined in three experiments in 1982–83. Virus-free bait plants, of potato and four other species, were exposed weekly to field infection during the growing season (March–June), and then returned to an aphid-free glasshouse for symptom expression. Only tobacco plants produced clear symptoms enabling reliable assessment of PVY infection pressure. When assessed with ELISA or by tuber indexing, the potato plants were efficient baits for both viruses whose infection period commenced at emergence (mid March to early April) and ended within 6–7 weeks. The seasonal trend of aphid populations, determined with Moericke traps or 100-leaf counts, correspond to that of virus spread. Correlation and regression analysis of aphid and virus data implicated the alate form ofMyzus persicae as the principal vector of both viruses.     

Improving production and health of seed potato stocks in Italy

Summary When nodal explants from sprouts grown from virus-free tubers of ten cultivars were propagated on half-strength Murashige and Skoog medium, cvs Arsy, Nicola, Kennebec and Spunta grew best. Rooted plantlets, 5–8 cm tall, were transplanted from culture vessels into pots containing soil, vermiculite and sand. They were weaned by growing in a glasshouse for about three weeks. Over 90% of the plantlets survived and these were then planted in the field and protected against aphids by a double screen (a large tunnel covering four adjacent small tunnels) and chemical treatments. Prebasic seed tubers thus obtained were virus-free and production ranged from 49.9 t.ha⁻¹ (‘Monalisa’) to 27.1 t.ha⁻¹ (‘Majestic’). A survey showed that ‘elite’ (near virus-free) seed could be produced from prebasic seed by early planting and early haulm killing regardless of location, but late planting on the plains and normal planting dates on the mountains resulted in 1 to 5% virus infection levels acceptable only for certified seed.     

Influence of physiological ageing of seed potatoes on yield and earliness

Summary Ageing seed potatoes at ambient temperatures after long storage (26 weeks) at 2 °C affected rate of plant emergence and yields of three potato cultivars in Cyprus. Sprout growth at ambient increased until planting, and was bigger in cv. Spunta than in cv. Arran Banner and cv. Cara. Four weeks after planting the rate of emergence was higher in physiologically younger seed; total emergence was not affected but average yields were reduced by ageing. Early yields were less affected but final yields were significantly reduced by ageing; these effects were moro pronounced in Spunta and Arran Banner, early and medium maturity cultivars respectively than in Cara, a late maturity cultivar. Ageing of seed at ambient temperature was rapid and removing seed to ambient for more than 3 weeks before planting to save storage costs adversely affected final yields.

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Zusammenfassung Eine nach verl?ngerter Lagerung bei 2 °C erfolgte Alterung der Saatkartoffeln bis zu 9 Wochen in der Umgebungstemperatur beeinflusste bei den Sorten Arran Banner, Spunta und Cara das Auflaufen der Pflanzen und die Ertr?ge. Das Keimwachstum wurde nach überführung aus dem Kaltlager in die Umgebungstemperatur bis zum Auspflanzen nicht unterbrochen; die Keime von Spunta waren l?nger als diejenigen von Arran Banner und Cara (Abb. 1). Bei physiologisch ?lterem Saatgut liefen die Pflanzen schneller auf als bei jüngerem (Tab. 1). Fünf Wochen nach dem Auspflanzen war die Auflaufrate in allen Behandlungen ?hnlich und gr?sser als 80 % (Tab. 1). Drei Wochen nach dem Auspflanzen war die Auflaufrate der Pflanzen durch die Alterung erh?ht. Die Zwischen- und Endertr?ge wurden durch die Alterung signifikant beeinflusst Saatgut, das l?nger als 3 Wochen in der Umgebungstemperatur gehalten wurde, erbrachte geringere Zwischen- und Endertr?ge. Die Frühertr?ge wurden durch die Alterungsbehandlungen weniger beeinflusst (Tabellen 2, 3 und 4). Die Saatkartoffeln alterten schneller nach überführung in die Umgebungstemperatur und ein Verbleiben des Saatgutes in der Umgebungstemperatur für mehr als 3 Wochen führt zu geringeren Ertr?gen. Wenn auch der Alterungsprozess w?hrend der Kaltlagerung fortschreitet, ist eine Verl?ngerung der Kaltlagerzeit wünschenswert, um dann das Saatgut in die Umgebungstemperatur zu übertragen und dadurch Lagerkosten zu sparen.

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Résumé Le vieillissement physiologique de plants de pomme de terre obtenu par la conservation à la température ambiante pendant des durées de 0 à 9 semaines après un maintien prolongé à 2 °C, affecte la levée et le rendement des variétés Arran Banner, Spunta et Cara. Après que les tubercules aient été sortis de chambre froide, la croissance des germes se poursuit jusqu'à la plantation. Les germes de Spunta sont plus longs que ceux d'Arran Banner et de Cara (fig. 1). La levée des plants est plus rapide chez ceux physiologiquement vieux que chez ceux physiologiquement jeunes (tableau 1). Cinq semaines après la plantation, le taux de levée est identique dans tous les traitements et dépasse 80% (tableau 1). La levée des plants trois semaines après la plantation est accrue par le vieillissement. Les rendements intermédiaires et finaux sont significativement affectés par le vieillissement. Les plants placés pendant plus de 3 semaines à température ambiante donnent de plus faibles rendements intermédiaires et finaux. La précocité des rendements est moins affectée par les traitements de vieillissement (tableaux 2, 3 et 4). Les plants vieillissent plus rapidement à la température ambiante et ceux conservés plus de trois semaines dans ces conditions donnent une réduction de rendement. Toutefois, le processus de vieillissement se poursuit également durant la période de conservation au froid aussi l'extension de la durée de cette période est préférable à cette de la mise à température ambiante lorsqu'elle est réalisée dans un but d'économie.

     

内蒙古西部区马铃薯脱毒种薯快速繁育的研究——Ⅱ.脱毒种薯生产技术及其良种繁育体系的研究

在内蒙古乌兰察布盟后山地区武川原种基地，对各级种薯生产技术及其良繁体系进行了系统的研究。现已明确：在开放条件下生产脱毒小薯（原原种），产量可达８０７３～９４６５ｋｇ／ｈｍ２，种薯产量和质量不低于温、网室生产的脱毒小薯；不同薯重的脱毒小薯旱坡地直播效果，以１０ｇ和８～１０ｇ薯重的效果好，产量和商品率均高；１级种薯在不同旱地类型种植的增产效果，以旱滩地的产量最高，其次为旱坡地，分别比对照（未脱毒）增产７１．２８％、１７１．２８％；８月上旬为有翅桃蚜迁飞盛期，从７月上旬迁飞初期开始喷药防蚜，防治效果显著；在乌盟后山半农半牧地区以原原种、原种、１、２级种薯建立的３级脱毒良种繁育体系符合该地区的生产实际，能达到留种和保种的快速、优质、高产、低成本的效果。经过６年示范推广，现已在武川等３个旗县普及，累计各级种薯种植面积达到２．３２万ｈｍ２，平均单产３万ｋｇ／ｈｍ２左右，生产出各级种薯及商品薯６９８５万ｋｇ，累计创造社会财富７１５０万元。     

Monitoring current season potato leafroll virus movement with an immunosorbent direct tissue blotting assay

A direct tissue blotting assay (DTBA) was used to track the movement of potato leafroll virus (PLRV) from newly infected foliage to the tubers. Plant and tuber characteristics were recorded to assess plant growth stage at inoculation and PLRV effect on yield. Russet Burbank potatoes were planted at different times in 1991 and 1992 to provide plants of different maturities which were then inoculated using PLRV carrying aphids. Aphids were allowed to feed two to three days after which an insecticide was applied. Stems and tubers were tested periodically for PLRV with DTBA after inoculation. Indexed tubers were grown out and ELISA tested in the greenhouse the following winter to confirm results of summer serological tests. Plant age affected percentages more consistently than did inoculation date. When plants approximately 43 days from planting were inoculated at different dates, early inoculation produced a higher percentage of infected plants. Conversely, when plants approximately 62 days from planting were inoculated at different dates, late inoculation resulted in a higher percentage of infected plants. However, early inoculation of young plants resulted in the highest infection percentages. Tuber size and yield were negatively affected by higher percentages of leafroll regardless of the stage of growth at inoculation. DTBA is best used for detecting PLRV in foliage of plants grown from infected tubers (i.e. secondary PLRV). DTBA is less accurate for detecting primary PLRV.     

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.     

Seed performance of Russet Burbank potatoes

A three-year study of three planting dates and four harvest dates of Russet Burbank seed potatoes was made to determine their effect on plant vigor, virus leaf roll infection, yield, size distribution and quality. Yields decreased significantly with delayed harvest of the seed crop. The incidence of late season virus leaf roll based on visual symptoms increased significantly with delayed harvests. The risk of a late season virus leaf roll infection increased when a later harvest was combined with a late planting. Seed taken from the earlier harvested plots consistently had earlier and more uniform emergence, the greatest vigor and the highest yields. The effect of planting date and harvest date had little effect on size distribution and no effect on specific gravity.     

Cryotherapy of Potato Shoot Tips for Efficient Elimination of Potato Leafroll Virus (PLRV) and Potato Virus Y (PVY)

Viral diseases constitute a major constraint to high yield and high quality production of potato. Potato leafroll virus (PLRV) and Potato virus Y (PVY) are among the most damaging potato viruses and are prevalent in most potato growing areas. In the present study, attempts were made to eliminate PLRV and PVY by three cryogenic protocols, i.e., encapsulation-dehydration, encapsulation-vitrification and droplet. Results showed that both PLRV and PVY could be efficiently eliminated by cryogenic treatments with 83–86% and 91–95% of frequencies of virus-free plantlets obtained for the former and latter, respectively. Frequencies of virus-free plantlets produced by cryogenic treatments were higher than those by meristem culture (56% for PLRV and 62% for PVY) and thermotherapy (50% for PLRV and 65% for PVY), and similar to those by thermotherapy followed by meristem culture (90% for PLRV and 93% for PVY). Survival (75–85%) and regrowth (83–89%) from cryo-treated shoot tips were higher than those from meristem culture (50–55%) and thermotherapy followed by meristem culture (40–50%), but similar to those from thermotherapy (80–87%). The morphology of the plantlets regenerated from cryo-treated shoot tips was similar to that of non-treated plantlets. Thus, cryotherapy would provide an alternative method for efficient elimination of potato viruses, and can be simultaneously used for long-term storage of potato germplasm and for production of virus-free plants.     

Trials to grow certified seed potatoes in the Golan Heights

Summary A trial to grow seed potatoes in summer 1968 in the Golan Heights indicated that hardly any aphid transmission of potato virus Y (PVY) could be noticed. Normal plant growth and tuber formation were observed. The incidence of seed borne virus diseases in fields grown from local seed produced in the Golan Heights in 1970 was: PVY 0.1–0.3% in 2 out of 33 inspected fields, potato leaf roll virus (PLRV) 0.3–2% in 19 fields. In 1972 30 fields were inspected, PVY was observed in 3 fields at a level of 0.1–0.2% PLRV at a level of 1–4% in 28 fields. Alfalfa mosaic visus (AMV) and Stolbur were not observed. The result of post-harvest control in field plots planted with seed potatoes produced in the Golan Heights in 1969, 1970 and 1971 were: PVY very low infection, 0.2–0.7%, for the three years; PLRV, low percentage, 0.3–0.7%, in 1970 and 1971, while it increased in 1972 to 1.3–6%. AMV and Stolbur were not observed.

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Zusammenfassung Die Felder auf den Golan-H?hen liegen 900 m ü. M. Die Temperatur ist tiefer als in den Ostgalil?ischen Bergen w?hrend des Sommers. Am 20. Mai 1968 wurden irische Pflanzkartoffeln der SorteUp-to-Date (anerkannt in Klasse A) in Merom Golan ausgepflanzt. In den Jahren 1969–1971 wurden im Mai Basispflanzen und Pflanzgut der Klasse A der SorteUp-to-Date an zwei verschiedenen Orten, Meron Golan und Ein Zivan, angebaut (Tabelle 2). In den Ergebnissen der Feldbesichtigungen, die 1969–71 2–3 mal in Juni/Juli durchge führt wurden, widerspiegelte sich ein offensichtliches Fehlen der Virus-Vektoren. Es wurde kaum eine Uebertragung des Kartoffelvirus Y (PVY) durch Blattl?use festgestellt mit einer Ausn?hme, n?mlich im September 1970, als eine verbreitete PVY-Infektion beobachtet wurde. Diese Parzellen unterstanden dem Seed Inspection Service, und der Ertrag wurde als zertifiziertes Pflanzgut verwendet. In den Jahren 1971–1972 wurden Muster von 100–200 Knollen in Pflanzgutgr?sse (40–100 g) zu verschiedenen Erntedaten entnommen und zu Untersuchungszwecken in einem insektensicheren Glashaus ausgepflanzt. Der durchschnittliche Virusbefall betrug 1971: PVY 1,3–2,6%, Kartoffel-Blattrollvirus (PLRV) 1,5–5,3%, Luzerne-Mosaikvirus (AMV) 6–12%, Stolbur 0–2% (Tabelle 2); 1972: PVY 1,3–2,5%. PLRV 0,5–4,6%, Stolbur war nicht vorhanden, AMV 2,5–4% (Tabelle 3). Pflanzgutmuster von den Golan-H?hen wurden 1970–72 in Versuchsparzellen angebaut. Der Virusbefall war wie folgt: PVY 0–0,7%, PLRV 0,3–6%, AMV 0–1% und Stolbur 0–0,5% (Tabelle 1). Vom Ertrag im Jahre 1970 wurden die Knollen in Pflanzgutgr?sse 1971 auf verschiedenen Feldern angebaut. Gem?ss dem Seed Inspection Service betrugen die Viruskheiten im Mittel: PVY 0,1–0,3% nur in 2 von 33 besichtigten Feldern; PLRV 0,3–2% in 19 Feldern, w?hrend das Virus in den andern 14 besichtigten Feldern nicht festgestellt wurde. 1972 wurden 30 Felder besichtigt, deren Pflanzgut im Sommer 1971 auf den Golan-H?hen erzeugt wurde. Befall mit Viruskrankheiten: PVY 0,1–0,2% in drei Feldern und keine Spur von PVY in den andern Feldern; PLRV 1–4% in 28 Feldern, und nur in 2 Feldern wurde kein sekund?res PLRV entdeckt. Die PLRV-Infektion ist also zunehmend h?ufiger aufgetreten und der Prozentsatz war h?her. Gelbscheckigkeit oder Calico infolge AMV oder Stolbur wurden in diesen 1971–1972 besichtigten Feldern nicht beobachtet. Die Ursache für diesen bedeutend geringeren Virusbefall auf den Feldern und den Kontrollparzellen, verglichen mit den Laboruntersuchungen, liegt in der Tatsache, dass eine betr?chtliche Zahl der AMV-infizierten Knollen nicht keimten oder unter Feldbedingungen nicht aufgingen. Pflanzen von PVY-infizierten Knollen neigen dazu, so früh aufzulaufen wie Pflanzen von gesunden Knollen; sie werden von ihren kr?ftigeren Nachbarn gedeckt und k?nnen daher den Augen des Anerkennungsexperten entgehen. Beurteilung von Pflanzkartoffeln von den Golan-H?hen. Im Frühling 1971 wurden Pflanzkartoffeln der SorteUp-to-Date von den Golan-H?hen im Vergleich met irischenUp-to-Date an neun verschiedenen Orten angebaut. An einem Ort war der Ertrag gleich, an vier Orten war er geringer und an den andern vier Orten h?her (Tabelle 6); w?hrend 1972 der Ertrag des Pflanzgutes von den Golan-H?hen gr?sser war mit dem gleichen Prozentsatz von grossen Knollen (über 60 g) (Tabelle 5). Die Pflanzkartoffeln von den Golan-H?hen verhalten sich wie Pflanzgut jüngerer Anbaustufen in bezug auf Auflaufen, Stengelzahl (Tabelle 4), Blühen und Knollenbildung.

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Résumé Les hauteurs de Golan se trouvent à 900 m audessus du niveau de la mer. Durant l'été la température y est plus basse que dans les montagnes de l'est de la Galilée. Le 20 mai 1968, on a planté à Meron Golan des plants irlandais certifiés A de la variétéUp-to-Date. Au cours des années 1969–1971, on a planté en mai des plants de base et des plants de classe AUp-to-Date dans deux localités différentes: Meron Golan et Ein Zivan (tableau 2). L'absence saisonnière apparente de vecteurs se reflète dans les résultats d'inspection des champs, exécutées 2–3 fois en juin-juillet 1969–71, ce qui explique qu'on n'a pu obsevver réellement aucune transmission par aphides de virus Y (PVY) sauf une fois où l'on observé, en septembre 1970, une infection réalisée en cours de saison. Les parcelles étaient soumises au contr?le du Service d'inspection des plants, et la production utilisée comme plants de pomme de terre certifiés. Au cours des années 1971–72, on a planté, en vue de tests, des échantillons de 100–200 tubercules de calibre ‘plants” (40–100 g), dans un abri toilé à l'abri des pucerons, et récoltés à différentes dates. En 1971, on a observé les viroses suivantes: PVY 1,3–2,6%, enroulement (PLRV) 1,5–5,3%, alfalfa (AMV) 6–12%, stolbur 0–2% (tableau 2). En 1972, les manifestations de viroses ont été les suivantes: PVY 1,3–2,5%, PLRV 0,5–4,6%, le stolbur étant absent, AMV 2,5–4% (tableau 3). On a planté des échantillons de plants provenant des hauteurs de Golan dans des parcelles expérimentales au cours des années 1970 et 1971. On a noté les viroses suivantes: PVY 0–0,7%, PLRV 0,3–6%, AMV 0–1% et stolbur 0–0,5% (tableau 1). En 1971, on a planté dans différents champs des tubercules de calibre ‘plants’ provenant de la production totale de 1970, les moyennes des maladies virologiques, selon le service d'inspection des plants, furent les suivantes: PVY 0,1–0,3% dans deux champs seulement des 33 champs inspectés, PLRV 0,3–2% dans 19 champs tandis qu'on a identifié aucune virose dans les 14 champs restants. En 1972, on a inspecté trente champs plantés avec des plants produits sur les hauteurs de Golan au cours de l'été 1971. Les manifestations virologiques ont été les suivantes: PVY 0,1–2% dans trois champs et aucune trace de PVY dans les autres; PLRV 1–4% dans vingt-huit champs et aucune manifestation de PLRV issu des plants dans deux champs seulement. L'infection de PLRV est donc devenue plus fréquente et le pourcentage d'infections plus élevé. On n'a pas observé de ‘Yellow mosa?c’ ou ‘Calico’ d? au AMV, ni de stolbur dans ces champs inspectés en 1971–1972. La raison de l'incidence remarquablement basse de virus dans les champs et parcelles de contr?le, comparativement aux tests de laboratoire, tient au fait qu'un nombre considérable de tubercules infectés de AMV ne germent pas ou ne lèvent pas dans les conditions des champs. Les plantes provenant de tubercules infectés de PVY ont tendance à lever aussi t?t que les plantes saines mais sont recouvertes par les plantes voisines vigoureuses. Elles peuvent par conséquent échapper aux yeux des contr?leurs. Appréciation des plants de pomme de terre des hauteurs de Golan. Au printemps 1971, on a planté, dans neuf localités différentes, des plants provenant des hauteurs de Golan, en comparaison avec des plantsUp-to-Date de provenance irlandaise. Dans une localité, la production fut identique, dans quatre localités elle était inférieur et elle fut supérieure dans les quatre autres (tableau 6); par contre en 1972 la production des plants des hauteurs de Golan était plus élevée avec le même pourcentage de gros tubercules supérieurs à 60 g (tableau 5). Les plants des hauteurs de Golan se comportent comme des plants plus jeunes eu égard à la levée, le nombre de tiges (tableau 4), la floraison et la tubérisation.

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Part of this paper was read at a session of the Virology Section at the 5th Triennial Conference of the EAPR (Norwich, September 1972).     

The effect of water stress on the yielding capacity of potato crops and subsequent performance of seed tubers

Summary The effect of water stress on yielding capacity of potatoes was studied in 3 years using four different levels of soil water potential (0.7, 1.9, 3.4 and 7.8 atm.) in experiments in specially adapted structures that excluded uncontrolled water supply. Seed tubers from these crops were planted in the following years to investigate effects of water stress on their subsequent performance. Limited soil moisture availability decreased yield and the number and size of tubers. The growing period was shortened by 1–4 weeks and dormancy period by 2–8 weeks. In the following year, seed produced under conditions of moisture stress gave plants with 20% fewer stems. 24–33% less yield, 18–22% fewer tubers and 19–22% fewer large tubers than plants from seed produced under abundant water supply. It is concluded that the yield potential of seed tubers can be improved by careful attention to the availability of soil moisture during their production.     

Reducing potato leaf roll virus (PLRV) in potato by means of baiting aphids to yellow surfaces and protecting crops by coarse nets

Summary Surrounding half of the perimeter of potato plots with sticky yellow polyethylene sheets (HPS) stretched vertically at a height of 0.6 m above the soil, reduced the number, of winged aphids by ca. 70% and of PLRV infection by ca. 38%. A YPS mulch cuased an increase in aphid population, PLRV incidence and percentage of misshapen tubers. Covers of white coarse net (2.5×8.0 mesh per inch square ≈ 1×3.1 per mesh per cm square) reduced landing aphids to ca. 2% of those trapped in unprotected plots but increased by factors of ca. 5 to 6000 the number of apterae. PLRV incidence was greatly reduced in protected plots provided that no secondary infection occurred under the net. In plots planted with secondarily PLRV-infected seeds subsequent incidence under the nets was even higher than in the unprotected controls. The use of aphicides in addition to net covers completely prevented the spread of PLRV.

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Zusammenfassung Um die Infektion mit PLRV in Kartoffelfeldern zu vermindern, wurde versucht, die anfliegenden L?use mit gelben Poly?thylenfolien (YPS) zu k?dern (die besonders im 500–700 nm Bereich des Spektrums reflektieren) und den Bestand mit weissen, grobmaschigen (1×3,1 F?den/cm²) und relativ billigen Netzen zu schützen. Eine Abdeckung mit YPS erh?hte die Zahl der insgesamt anfliegenden L?use und die Zahl der gefangenenMyzus persicae (Abb. 1). Der Befall mit PLRV war in behandelten Parzellen 2,1% im Gegensatz zur Kontrolle mit 0,6%, die Zahl der missgestalteten Knollen verdoppelte sich durch diese Behandlung. Wurde die halbe Parzelle mit einer klebrigen YPS (2m×0,5m) abgeschirmt, die ausserhalb der Parzelle senkrecht in einer H?he von 0,6 m über dem Boden aufgespannt war, so verringerte sich sowohl die Blattlauspopulation als auch der Befall mit PLRV. Die Zahl der insgesamt anfliegenden L?use und die Zahl der geflügeltenM. persicae betrug in den geschützten Parzellen nur ca, 30% der in den Kontrollen gefangenen (Abb. 1, Tabelle 5) und der Befall mit PLRV wurde in 5 von 6 Versuchen auf 29–87% des in den entsprechenden Kontrollen beobachteten gesenkt (Tabelle 1). Dennoch war der Befall in den geschützten Parzellen noch h?her als in der Pflanzgutverordnung erlaubt (Tabelle 1). Abdeckungen mit doppelten Lagen von Netzen reduzierten den L?useanflug auf ca, 1% der in den unbedeckten Kontrollen gefangenen (Tabelle 5) und verhinderten vollst?ndig die Ausbreitung des PLRV. Billigere Abdeckungen mit einfachen Lagen von Netzen wurden in gr?sserem Umfang getestet (9 Versuche). In allen Versuchen wurde die Zahl der geflügelten L?use signifikant auf 1,4–2,6% der in den Kontrollen landenden gesenkt. Unter dem Netz stiegen jedoch, vor allem gegen Ende der Wachstumsperiode die Populationen der ungeflügelten L?use stark an, (Tabelle 3). Die Ausbreitung des PLRV war unter den Netzen stark eingeschr?nkt, unter der Voraussetzung, dass keine Sekund?rinfektion vorhanden war, im anderen Fall führte die unter dem Netz entstehende starke Blattlauspopulation zu einer verst?rkten Virusausbreitung (Tabelle 2). Die Netzabdeckung hatte keinen Einfluss auf den Gesamtertrag (Tabelle 6). Eine Kombination zwischen Netzabdeckung und Insektizideinsatz verhinderte die Ausbreitung des PLRV vollst?ndig, w?hrend in den ungeschützten und nicht gespritzten Parzellen 16% Knollen mit PLRV gefunden wurden (Tabelle 4). Es sollte daher m?glich sein, unter dem Netz und mit Insektizideinsatz Pflanzgut mit geringem PLRV-Befall zu erzeugen.

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Résumé Des essais ont été réalisés pour réduire l’infection d?e au virus de l’enroulement (PLRV) dans les parcelles de pommes de terre, soit en attirant les pucerons par des baches en polyéthylène jaune (ces baches jaunes réfléchissent la lumière dans la zone des 500–700 nm), soit en protégeant la culture par des filets blancs grossiers (1×3,1 fils par cm²). Un paillis réalisé avec les baches en polyéthylène jaune augmente le nombre total de pucerons et le nombre deMyzus persicae piégés (fig. 1). L’incidence du PLRV dans les parcelles traitées est plus importante que dans les parcelles témoins non traitées: 2,1% contre 0,6%, et le nombre de tubercules difformes est doublé par ce traitement. On entoure la moitié du périmètre des parcelles avec des baches de polyéthylène jaune (2m×0,5m), enduites de colle, placées à une hauteur de 0,6 m au-dessus du sol. Ceci réduit à la fois la population aphide et l’incidence du PLRV. Dans les parcelles protégées, le nombre total de pucerons et le nombre deM. persicae ailés représentent 30% de la population piégée dans les parcelles témoins (fig. 1, tableau 5). Dans cinq des six essais, l’incidence du PLRV est réduite à 29–87% par rapport à celle détectée dans les parcelles témoins (tableau 1). Cependant, l’incidence du PLRV dans les parcelles protégées est encore plus élevée que les niveaux permis pour la certification des semences (tableau 1). Dans des parcelles couvertes d’une double épaisseur de filet, le nombre de pucerons ailés représente 1% du nombre piégé dans les parcelles témoins (non couvertes) (tableau 5); l’infection d?e au PLRV ne se propage pas. La protection des parcelles avec une seule épaisseur de filet (cela revient moins cher) a été testée sur neuf essais. Dans tous ces essais, le nombre total de pucerons ailés est réduit de fa?on significative à 1,4–2,6% par rapport au nombre obtenu dans les parcelles témoins. Cependant, les populations de pucerons aptères augmentent sous le filet, notamment à la fin de la saison (tableau 3). La propagation du PLRV, favorisée par le développement d’importantes populations d’aptères (tableau 2) est notablement réduite sous le filet si aucune infection secondaire ne se manifeste. En outre, les filets n’affectent pas le rendement total (tableau 6). En combinant la protection des parcelles par des filets avec un traitement aphicide, on empêche totalement la propagation du PLRV, alors que dans les parcelles non protégées et non traitées on détecte 16% de tubercules virosés (tableau 4). Donc, une protection par des filets plus un traitement aphicide permettraient aux plants de pommes de terre de se développer avec un taux d’infection relativement faible.

     

Relationships of defined PVX infection levels to verticillium wilt,yield, and quality of the Russet Burbank potato

Field studies were conducted over a three-year period to investigate effects of potato virus X (PVX) on the Russet Burbank potato cultivar. Seed (PVX-free and PVX-infected) used for this three-year study originated from the same PVX-free source and was grown and stored under similar conditions. PVX-free seed was found to increase yield over PVX-infected plots by 9 to 32%. With these yield benefits, effects of PVX on either the incidence of verticillium wilt or plant nutrition were not significant. There was a trend (P = 0.10) for a reduction of mean tuber weight when the PVX infection level exceeded 19%. Because of increases of undersized potatoes, the yields of U.S. #1 potatoes were reduced as levels of PVX infection were increased. With a PVX infection level of 36%, the yield of U.S. #1 tubers was reduced by 21% when compared with plots having 0% PVX. At an 88% infection level, the yield of U.S. #l’s was reduced still further (36% lower than plots with 0% PVX). Results demonstrate the importance of the level of PVX infection to potato production.     

Foliar Symptoms Caused by Potato mop-top virus on Potato Plants During Vegetative Propagation in Scotland and Their Association With Tuber Yield, Spraing and Tuber Infection

The effect of foliar symptomatic infection by Potato mop-top virus (PMTV) on yield of tubers, spraing and infection in daughter tubers, and foliar symptom development and tuber infection in the following generations of propagation was investigated in commercial seed potato crops in Scotland. Six crops covering cvs Atlantic, Hermes, Nicola and Cara were studied between 2000 and 2006 by labelling paired replicates of plants with foliar symptoms and plants with no symptoms. Tubers from plants with no symptoms rarely produced plants with foliar symptoms in the following generation. Plants with no symptoms produced more infected tubers if they had been derived from plants with foliar symptoms the previous year than from plants with no symptoms. The proportion of daughter plants with foliar symptoms produced by tubers from plants with foliar symptoms in year 1 ranged from 19–41% and seemed to be associated with the severity of foliar symptoms. The detection of PMTV by ELISA in samples of leaves from plants with foliar symptoms ranged from 13% for cv. Cara to 59% for a crop of cv. Atlantic in 2004. The amounts of spraing were generally low but tended to be greater for tubers from plants with foliar symptoms than those from plants with no symptoms. These results indicate that roguing plants with foliar symptoms in seed potato crops could achieve an improvement in crop health but might be impractical when diseased plants are too prevalent.     

马鈴薯脱毒种薯早收试验

1984～1985年,作者在北京延庆县田间观察马铃薯脱毒种薯早收对减少种薯感染病毒的效果。在桃蚜迁飞高峰后10～15天割秧的(以下简称割秧)病毒感染率很低:1984年0.08～0.25%;1985年1.17～1.50%。不割秧的病毒感染率很高:1984年0.83%;1985年3.30%。翌年挖取芽眼经病毒提取作PVX、PVY和TMA血清鉴定,割秧者呈阴性反应,不割秧者呈阳性。翌年将所得种薯栽种田间目测病毒症状,割秧者未见症状,不割秧者病毒株率5.5%。割秧每亩8000穴的亩产10克以上的种薯块数达32240～37600块,而不割秧正常密度的亩产10克以上种薯块数只16400～26800块。因此,早割秧密植不仅可以减少病毒感染,而且利于加大种薯繁殖系数。