Variation in the duration of tuber dormancy within a seed potato lot

Summary The variation in duration of dormancy within a seed tuber lot was studied over three years by harvesting individual plants of cvs Diamant and Désirée from field plots and by storing the tubers at 18°C. The variation in dormancy within a tuber lot was large (especially for cv. Diamant) and was mainly caused by variation within plants. For cv. Diamant there was a close negative relation between dormancy and the cube root of tuber weight, whereas for cv. Désirée a relation with tuber weight was almost absent. The duration of dormancy of a seed lot comprising tubers with a narrow range in weight can be well described by two parameters. It is proposed to maintain the moment of 80% sprouting as the criterion for the end of dormancy of a tuber lot and to characterize the spread in dormancy duration by the time lapse between 10% and 90% sprouting.     

Intercellular spaces enhance potato tuber elasticity

Summary The intercellular volume within tuber tissue increases with tuber maturation. At the same time, both tuber injury after mechanical load and lentical perforation after water uptake by tubers in wet peat decreases. The degree of tuber injury is correlated with intercellular space (r=−0.667,n=16) and with water saturation of tissue (r=0.697,n=16). The tubers lose water during storage. In wet soil wilted tubers take up significantly higher amounts of water than turgid tubers, and lenticel perforation is much more frequent. Tuber maturation in autumn and low water loss during storage enhance the cushioning effect of the intercellular gas volume of tuber tissue against outside mechanical load and internal tension after water uptake.     

Tyrosine synthesis in potato tuber tissue from blackspot-susceptible and resistant genotypes

Summary Radioactively-labeled shikimic acid (¹⁴C) was incubated with potato tuber tissue disks to determine the relative rate of tyrosine synthesis in blackspot-resistant and susceptible cultivars. Tyrosine synthesis was 55% higher in the susceptible cultivar, Lemhi Russet, than the resistant clone TXA 763-5. The susceptible clone also partitioned a lower percentage of¹⁴C tyrosine into soluble protein than did the resistant genotype. The percentage of labeled free tyrosine which would be available for oxidation by polyphenyloxidase was therefore much higher in the susceptible cultivar. Hort/LA Paper No. 90-27. Project No. 0766. Washington State University, College of Agriculture and Home Economics Research Center, Pullman, WA 99164     

Differential resistance to tuber late blight in potato cultivars without R-genes

Summary In 1983 and 1984 there were reports in Norway of more severe late blight infection than usual on tubers of cv. Pimpernel, a cultivar without R-genes known to be somewhat resistant to both haulm and tuber infection. Results from routine tests confirmed earlier experience that cv. Pimpernel shows stable resistance to tuber late blight, although the ranking of cultivars may vary between years. In experiments during three harvest seasons tubers of different cultivars were inoculated with isolates ofP. infestans obtained from stocks of cv. Pimpernel with severe tuber late blight and with other isolates. In these experiments the isolates from cv. Pimpernel caused more rot on tubers of Pimpernel than did other isolates.     

Solanum × berthaultii,a sensitive host for indexing potato spindle tuber viroid from dormant tubers

Summary When infected with mild and severe strains of potato spindle tuber viroid (PSTV), some clones ofSolanum × berthaultii developed severe symptoms, consisting of necrotic spotting of petioles and main stems and of leaf collapse. The necrotic, rolled leaves eventually dried and remained attached to the stem, any new leaves were small and the plant was severely stunted. Symptoms developed after inoculation with sap from potato foliage, sprouts, or tubers. Tubers could be indexed immediately after harvest or after storage. Single tubers could be tested by rubbing onto leaves ofS. × berthaultii either the cut surfaces of the suspect tuber directly or an extract of nucleic acid. Crude tuber extract proved unsatisfactory for inoculation. PSTV infection could be detected from as little as 31 to 7 mg of infected tuber tissue mixed with 1969 to 1993 mg of healthy tuber tissue (at a dilution factor of 64 to 256).

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Zusammenfassung Nach Infektion mit einem schwach oder stark aggressiven Stamm des Kartoffel-Spindle-Tuber-Viroids (PSTV), zeigten einige Klone vonSolanum x berthaultii die Entwicklung starker Symptome. Dabei ergaben sich nekrotische Flecken an Petiolen und Haupttrieben, begleitet von Kollabieren der Bl?tter. Die nekrotischen, eingerollten Bl?tter trocknen schliesslich aus, brechen jedoch nicht ab oder fallen herunter (Abb. 1). All neu entstehenden Bl?tter sind im Wachstum reduziert, die ganze Pflanze ist stark gestaucht. Symptome erscheinen nach Inokulation mit Saft aus Bl?ttern, Trieben oder Knollen (Tab. 1). Knollen konnten sowohl durch Abreiben der Schnittfl?chen der zu untersuchenden Knollen direkt auf Bl?tter oder durch Abreiben mit einem Extrakt von Nukleins?ure getestet werden (Tab. 1, 2). Rohe Knollen-Extrakt war nicht geeignet für Inokulation, aber rohe Sprossextrakt war ebenso brauchbar wie Knollen-Nukleins?ure (Tab. 1). PSTV-Infektion konnte noch bei Mischung von 31 bis 7 mg infizierten Gewebes mit 1963 bis 1993 mg gesunden Knollengewebes ermittelt werden (Tab. 2). Das Verh?ltnis von infiziertem zu gesundem Gewebe ist ?quivalent mit einer infizierten Knollen zu 63 bis 255 gesunden Knollen oder einem Verdünnungsfaktor von 64 zu 256. Bei Verwendung vonS. x berthaultii konnte PSTV von Knollen ermittelt werden, die von Kartoffelpflanzen abstammten, welche mit stark verdünntem PSTV-Inokulat behandelt worden waren (Tab. 3); es ist also m?glich, PSTV an im laufenden Jahr infizierten Kartoffelpflanzen zu entdecken. In einer Untersuchung von im Feld aufgewachsenen PSTV-verd?chtiger Knollen, konnte PSTV sowohl bei Knolleninfektion mit mild als auch stark aggressiven St?mmen ermittelt werden (Tab. 4). S. x berthaultii kann leicht bei Herstellung von Stengelabschnitten verbreitet werden. Ein Klon (Klon 26), der im Rahmen dieser Arbeit entwickelt wurde und einheitlich in Wachstum und seiner Reaktion gegen PSTV ist, sollte für den PSTV-Test verwendet werden. Diese Arbeit vermittelt ausserdem eine Methode zur Entwicklung weiterer PSTV-sensitiver Klone mitS. x berthaultii-Anteil, wenn Pflanzenquarant?ne-Regulierungen den Import fremderSolanum-Arten verbieten.

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Résumé Certains cl?nes deS. x berthaultii ont donné des sympt?mes graves après contamination par souches peu ou très agressives du viro?de en fuseau de la pomme de terre. Les sympt?mes se manifestent par des taches nécrotiques sur les pétioles et les tiges principales, avec un affaissement du feuillage. Les feuilles nécrosées et enroulées peuvent éventuellement se dessècher, mais elle restent attachées à la plante (fig. 1). La croissance de quelques jeunes feuilles est ralentie et la plante entière reste très chétive. Les sympt?mes appara?ssent après inoculation de jus obtenu à partir des feuilles, des germes ou des tubercules de pomme de terre (tableau 1). Les tubercules douteux pourraient être testés soit par frottis des surfaces coupées directement sur les feuilles soit par frottis avec un extrait d'acides nucléiques (tableaux 1, 2). L'extrait brut de tubercules ne donne pas entière satisfaction, alors que l'extrait de germes permet d'obtenir d'aussi bons résultats que l'extrait d'acides nucléiques provenant de tubercule (tableau 1). L'infection du viro?de en fuseau dans les tubercules peut être décelée pour des quantités faibles allant de 31 à 7 mg de tissu infecté et mélangé à une quantité allant de 1969 à 1993 mg de tissu de tubercules sains (tableau 2). Le rapport tissue infecté sur tissue sain équivaut à 1 tubercule infecté dans un lot de 63 à 255 tubercules sains, soit un facteur de dilution de 64 à 256. Le viro?de en fuseau a été détecté en utilisantS. x berthaultii à partir de tubercules provenant de plants infectés par un inoculum du viro?de très dilué (tableau 3). Mais il est préférable de le déceler dans la même année sur plantes contaminées. Au cours d'un contr?le d'essai de plein champ réalisé sur tubercules douteux, le viro?de en fuseau a été décelé sur des tubercules contaminés par des souches peu ou très virulentes (tableau 4). S. x berthaultii se multiplie facilement par boutures et un cl?ne (cl?ne 26) expérimenté dans cette étude a montré une croissance régulière et une réaction uniforme au viro?de en fuseau; il peut être ainsi utilisé pour tester le viro?de en fuseau de la pomme de terre. Cette étude peut servir également à rechercher d'autres cl?nes sensibles au viro?de et issus deS. x berthaultii, supprimant ainsi l'importation d'espèces étrangères deSolanum soumises à une mise en quarantaine.

     

A comparison of tuber shape and tissue composition of potato genotypes

Summary Seven tuber attributes were measured for a number of cultivars and breeding lines: two shape indices for the length and flatness of the potato, one index for the narrowness of the pith, three volume parameters for the relative proportion of cortical, perimedullaryand pith zones of the potato, and specific gravity. The three index traits, specific gravity and volume of the pith zone showed highly significant genotype x year interactions. Significant genotypic and seasonal effects were usually detected for the three volume traits and specific gravity. The percentage volume of the cortical and perimedullary zones showed no genotype x year interactions. Correlations between the traits were estimated, and a factor analysis was performed based on the correlation matrix. One factor appeared to control the negative allometric relationship between the percentage volumes of the cortical and perimedullary zones, and another factor indicated the relationship between the length and flatness indices of the potato. The negative association of the percentage volume with the narrowness index of the pith and positive association between the length of tuber and narrowness of the pith suggested that long potatoes having narrow pith were inclined to have a smaller volume of pith. Factor analysis can be used to identify genotypes with desirable tuber attributes.     

Chemiluminescent detection of potato spindle tuber viroid in true potato seed using a digoxigenin labelled DNA probe

Summary The potential use of a simple, sensitive and non-radioactive method for detecting potato spindle tuber viroid (PSTVd) in germinated true potato seeds, based on nucleic acid hybridization with a PSTVd-specific DNA probe labelled with digoxigenin, was investigated. Two simple procedures for the clarification of plant extracts suitable for a non-radioactive detection system were also investigated. The nucleic acid hybridization technique could detect one PSTVd-infected seed in more than 150 healthy seeds. The benefits of this non-radioactive detection system are discussed.     

A method of assessing potato seedling progenies for resistance to the white potato cyst nematode

Summary The resistance expressed by progenies of potato seedlings to the white potato cyst nematode (Globodera pallida) has been assessed on bulk sowings of seedlings and on individual plants raised from tubers, and a positive correlation between the seedling and plant tests has been established. The use of such a seedling test as an addition to other methods of screening is discussed.     

Wound healing in potato tuber tissue. 2. Varietal and anatomical variation

Summary The wound healing potential of 15 UK maincrop potato cultivars was assessed from the ability of discs of cortical and medullary tissue to become resistant to the loss of water vapour, as their surfaces suberized. Varietal rankings were moderately consistent over four experiments in two years, with cvs Désirée, Bintje and Pentland Hawk showing rapid healing and Majestic, Redskin and Pentland Crown rather slow healing. Wound healing rates in cortical and medullary tissue were generally similar. Since fast wound healing is not the dominant mechanism of resistance to disease, correlations with established ratings for resistance to individual diseases were not found, but some protection against a broad spectrum of storage diseases is likely. Wound healing rankings correlated with varietal resistance to mechanical damage.

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Zusammenfassung Die Versuche sollten sortenbedingte Unterschiede bei Wundheilungs-Raten demonstrieren. Ausserdem galt es herauszufinden ob sich Unterschiede im Wundheilungs-Potential zwischen Rinden- und Markgewebe ergeben, wodurch sich die relative Bedeutung von flachen gegenüber tiefen Wunden darstellen würde. Der Anstieg in der internen Widerstandsf?higkeit im Hinblick auf Verlust von Wasser-Dampfdruck von Scheiben von Knollengewebe, ein Mass für die Suberinisierung an Wundoberfl?chen, wurde über 6–9 Tage in vier Versuchen über zwei Lagerperioden verfolgt. Die 15 untersuchten sp?ten Kartoffelsorten zeigten betr?chtliche sortenbedingte Abweichungen in allen vier Experimenten (Tabellen 1 und 2). Zwischen den beiden Perioden waren die Schwankungen nur gering, ebenso zwischen den Untersuchungen im Herbst und im Frühjahr (Tabelle 3). Die H?he des Wasserverlustes bei Rinden- und Markgewebe waren im wesentlichen gleich (Tabelle 2) und korrelierten zwischen den Sorten (r=0,84,P<0,001). In den ersten 4–5 Tagen der Inkubation entwickelte sich die interne Widerstandsf?higkeit gegen Wasserverlust z?gernd, bei ungef?hr 6 Tagen dann schneller (Abb. 1). Sowohl das Ausmass des schnelleren Anstiegs als auch die Zeit des Beginns bestimmten den generellen Grad an Resistenz gegen Wasserverlust über die gesamte Inkubationsperiode (Abb. 1). Sorten mit rapider Wundverheilung in diesen Untersuchungen, z.B. Désirée und Bintje, befanden sich unter denjenigen, welche von Blight & Hamilton (1974) mit geringer Anf?lligkeit gegen mechanische Besch?digung eingestuft worden waren.

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Résumé Le but de cette étude est de mettre en évidence l'importance des variations dans le taux de cicatrisation des blessures selon les variétés et de rechercher s'il existe une différence dans le potentiel de cicatrisation entre les tissus corticaux et médullaires qui pourraient déterminer l'importance relative des blessures légères et profondes. L'augmentation de la résistance interne à la perte en vapeur d'eau à partir de lamelles de tissus de tubercules, comme mesure de subérisation des surfaces blessées, a été suivie pendant 6 à 9 jours dans 4 expérimentations au cours de deux campagnes de conservation. Les 15 principales variétés testées ont montré un degré variétal important dans les 4 essais (tableau 1 et 2). Le classement des variétés n'a guère varié d'une année à l'autre et entre automne et printemps (tableau 3). Les taux de perte en eau des tissus médullaire et cortical sont en général équivalents (tableau 2) et correlés avec les variétés (r=0,84,P<0,001). La résistance interne à la perte en eau évolue lentement les 4–5 premiers jours d'incubation, et plus rapidement après 6 jours environ (fig. 1). La variation dans la phase rapide, et dans sa date de démarrage détermine le niveau global de résistance à la perte en eau pour toute la période d'incubation (fig. 1). Les variétés qui montrent une évolution rapide de cicatrisation dans cette étude, telles que Désirée et Bintje, sont parmi celles estimées par Blight & Hamilton (1974), qui présentent une faible sensibilité à l'endommagement mécanique.

     

Methods to increase the starch content of potato tuber callus tissue

Summary Attempts were made to increase the starch content of callus tissue from tubers of cvs Lemhi Russet and Russet Burbank by varying growth regulator concentration, sugar source, sugar concentration, temperature and callus shape. Starch content was always higher in media containing no growth regulators. Callus spread over the media contained more starch than unbroken rectangular or cube-shaped callus. Sucrose was superior to glucose and fructose for starch formation. A sucrose concentration of 20 % produced more starch than lower concentrations. Callus growth decreased as the sucrose concentration increased. ‘Lemhi Russet’ callus incubated with 8 % sucrose at 20, 25 and 30 °C contained 1.2, 0.4 and 0.8 % starch respectively, which was much higher than in ‘Russet Burbank’ callus. With varying amounts of mannitol as an osmoticum in 8 % sucrose, the most starch was found in the medium containing 5 % mannitol. Research Paper 92B2 of the Idaho Agricultural Experiment Station     

Expression and activity of antioxidant enzymes during potato tuber dormancy

Summary The expression of antioxidant genes has been analyzed in a potato plant and during tuber dormancy. Manganese superoxide dismutase (MnSOD), cytosolic copper and zinc superoide dismutase (Cu/ZnSOD), catalase class II, cytosolic ascorbate peroxidase (APX) and glutathione peroxidase (GPX) are expressed at the RNA level in all the contexts analyzed. By contrast, the expression of the iron superoxide dismutase (FeSOD) and plastidic Cu/ZnSOD seems to be limited to green tissues, as shown by northern blots and native gels. A complex DAB-peroxidase isozyme pattern (using diaminobenzidine as substrate) has been observed in different developmental contexts analyzed, but hardly observed in tubers. During tuber dormancy, MnSOD and cytosolic Cu/ZnSOD activity was relatively constant in both Désirée and Bintje varieties while catalase activity decreases. Moreover, tuber dormancy breakage did not involve significant changes in the activity of these enzymes. On the basis of these results, the possible link between active oxygen species (AOS) metabolism and dormancy is discussed.     

Aspects of nitrogen fertilizer rate on tuber dry-matter content of potato cv. Record

Summary Effects of three rates of fertilizer nitrogen, viz. 80, 160 and 240 kg N/ha, on tuber yield and dry-matter percentage in potato cv. Record were compared in two experiments. Crop nitrogen uptake increased with application rate but total uptake differed between experiments. Tuber yield was highest following application of 160 or 240 kg N/ha but differences between these two rates were not significant. Tuber dry-matter percentage was reduced in one experiment with increasing nitrogen rate, but in the second experiment final dry- matter percentage was highest following application of 240 kg N/ha. In all treatments, positive linear relationships were found between dry matter percentage and mean fresh weight of tubers >30 mm, but within experiments, the regression coefficients were generally reduced by increased crop nitrogen uptake.     

A simple and rapid method for the detection of potato spindle tuber viroid (PSTVd) by RT-PCR

Summary A test procedure for PSTVd is described based on immobilisation of plant sap on filter paper, by dotting or tissue printing followed by RT-PCR. Tests were carried out using primarily and secondarily infected potato plants, primarily infected in vitro plants, and potato tubers. Print PCR was shown to be suitable for testing large samples of potato plants whereas dot PCR is recommended for in vitro plantlets and tuber tissue. Bulking one infected plant to 4 or 9 healthy plants gave reliable results with secondarily infected potato plants, but sometimes the test failed to detect PSTVd in primarily infected in vitro plants. Dotted and printed paper squares could be stored at 4°C for at least 2 weeks in Triton X-100 solution or under dry conditions. Storing at room temperature can lead to unreliable results.     

Screening potato cultivars for common scab of potato in a naturally infested field

Summary Twenty seven cultivars of potato were screened for common scab grown in a commercial field in two successive years (1996–97 and 1997–98). Eight cultivars were least susceptible and the others ranged from medium susceptible to very highly susceptible. None of the cultivars was resistant. Most showed a stable resistance reaction in both years.     

Determination of natural and wound-induced potato tuber suberin phenolics by thioglycolic acid derivatization and cupric oxide oxidation

Summary Application of two lignin chemistry techniques, CuO oxidation and thioglycolic acid derivatization, has confirmed that natural and wound-induced suberin does have a lignin-like component. The time course of suberin phenolic deposition could be monitored by using the thioglycolic acid technique. The thioglycolic acid procedure is easily performed, can be adapted readily to multiple samples, and thus could be an effective tool for studying rates of wound-induced suberization.     

Verification of sap flow by heat balance method on three potato cultivars

Summary A heat balance method for measuring sap flow in actively growing plants was tested on three potato (Solanum tuberosum L.) cultivars Monona, Norchip and Atlantic. The method is based on applying a known heat source to the stem of an intact plant: by measuring the axial and radial heat dissipation the magnitude of sap flow can be quantified. The technique shows promise as 24 h accumulated sap flow measurements were highly correlated (r²=0.935, n=36) with gravimetric measurements of transpiration and produced an average root mean square error (RMSE) of 20 g d⁻¹. The accuracy of the method improved as daily accumulated flow increased. Under low daily flow rates overall RMSE increased, supporting the need for a heat storage term in the heat balance equation. Short term flow rates were less significantly correlated (r²=0.764, n=1572) and produced an average RMSE of 2.89 g h⁻¹. Identification of these short term flow rates during high flow periods may be difficult. The presence of water potential gradients and the likelihood of re-hydration during high flow events may have also affected the short term performance of the method. At low flow rates, many different errors may be introduced.     

The role of phenols in potato tuber resistance against soft rot byErwinia carotovora ssp.carotovora

Summary Increasing doses of nitrogenous fertilizer increased storage rots in six potato cultivars of which cvs Kufri Sindhuri and Kufri Lalima rotted less and were found to contain high amounts of total phenols compared to the more susceptible cultivars Kufri Jyoti and Kufri Badshah. Nine phenolic acids were identified in the peel and the pulp of tubers and four of these and of other phenolic extracts from tubers suppressed the growth ofErwinia carotovora ssp.carotovora. Research Publication No. 5811, Experiment Station, G.B.P.U.A. & T., Pantnagar 263 145, India.     

Tuber yield and tuber quality of several potato cultivars as affected by seasonal high temperatures and by water deficit in a semi-arid environment

Summary The effects of high temperatures and water deficit on potatoes were investigated under field conditions. Nine cultivars and one un-named seedling were grown in the spring and in the summer under high temperatures. In both seasons the cultivars were grown under 3 water regimes: adequate water supply, moderate water deficit, and severe water deficit that were achieved by a modification of the single line source sprinkler irrigation system. Severe drought reduced tuber yields in both seasons. Moderate tolerance to a moderate water deficit in the spring season was exhibited by Draga, Désirée, and Monalisa. Late and intermediate cultivars produced high tuber yields in the spring season, and early cultivars had relatively smaller yield losses in the summer. The extent of tuber disorders, sprouting, rotting and malformation, varied considerably. High temperatures enhanced sprouting, rotting and malformation and drought may enhance sprouting and malformation. This investigation was supported by a grant from the Ministry of Foreign Affairs, Technical Assistance Department, Netherlands.     

Estimating tuber dry matter concentration from accumulated thermal time and soil moisture

Summary The tuber dry matter concentration, [DM], of crops of potato (Solanum tuberosum L.) was related using regression analysis, to time, thermal time, incident radiation accumulated from plant emergence, and soil moisture deficit (SMD). Variation in [DM] was best accounted for by the regression model that was a function of thermal time above a base of 0 °C accumulated from plant emergence, and SMD. When validated against an independent data set, there was good agreement between observed and estimated [DM] with a linear relation accounting for 79.3% of the variance.     

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.