Some effects of plant spacing on potato quality

Summary As plant population was increased so the dry matter content of the tubers increased, but delaying harvest had little such effect. Tubers of 2–3 cm (or 2.5–3.0 cm) had a lower dry matter content than tubers of 4.5–5.5 cm size at any one harvest. Increases in dry matter content were associated with increases in the disintegration of the tubers when cooked. The N content of the tubers was influenced by population, and although N content decreased and after-cooking blackening decreased with increasing plant population, after-cooking blackening was better related (inversely) to the K/N ratio of the tubers than to N content. Tubers from the later harvests had higher N, lower K and lower K/N ratio than those of a similar size at the earlier harvests. Published effects of fertilizer application on quality are related to similar effects obtained by varying the plant population.     

Effect of variety and harvest date on tuber sugars and chip color

The major tuber sugars—glucose, fructose and sucrose — in tubers of the Red Pontiac, Kennebec and Monona potato varieties harvested five times during the 1970 growing season were determined quantitatively by a gas-liquid Chromatographic technique. Also, chips were made from tubers and chip color was measured objectively and reported as Rd values. Red Pontiac tubers produced the darkest-colored chips (Rd-15.5), and its tubers tended to accumulate the highest levels of the three sugars. The major difference between Monona, which produced chips with the lightest color (Rd-21.1), and Kennebec (Rd-19.5) was the very low level of glucose found in the tubers of Monona. Varieties produced chips lightest in color at the second (8/31) or third (9/15) harvest dates. Conversely, darkest-colored chips were obtained from each variety at the fourth harvest date (9/28). This was attributed to the cool, wet weather. Sugar content also varied during the harvesting schedule. Glucose content changed little until late in the season when an increase occurred. Fructose tended to decline until the final harvest when a distinct increase was obtained. Sucrose declined significantly through the third harvest, but changed little thereafter.     

Specific gravity and dry matter content of potato

Summary Data obtained from 516 pairs of specific gravity and dry matter determinations were used to derive a relationship for estimation of dry matter content of potatoes grown in India.     

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 effect of time of harvest,variety and storage of the ascorbic acid content of potato tubers

American Journal of Potato Research -     

Specific gravity,potato chip color and tuber mineral content as affected by soil moisture and harvest dates

In 1966 and 1967 the chipping quality of three potato varieties was studied using three moisture regumes, two nitrogen levels, and three harvest dates. Specific gravity and chip color of potatoes freshly harvested and of those stored 10 days, along with chip color differences between the two periods, were tested. Of the three varieties tested — Anoka, Kennebec, Irish Cobbler — Anoka§ specific gravity was least depressed by soil-moisture stress and its chip color least affected by time of chipping; all tubers, however, chipped darker after being stored. High soil temperatures were associated with low specific gravities and dark chips. In 1966 irrigation tended to lower soil temperature, resulting in lighter chip color for potatoes harvested from irrigated than from nonirrigated plots; also color was lighter at the first than at the later harvests. In 1967, when air temperatures were consistently lower and rainfall nearly adequate, chip color was lighter for potatoes harvester later in the season. Nitrogen levels did not influence chip color. Moisture regimes and varieties influenced mineral content of tubers more consistently for the two years than did harvest dates or nitrogen levels. Specific gravity did not correlate significantly with chip color.     

Population density and row spacing effects on dry matter yield and bark content of kenaf (Hibiscus cannabinus L.)

Efforts to bring kenaf from experimental crop status to an accepted alternative in established cropping systems have been ongoing for years. To compete with existing crops and maximize monetary returns, the effects of agronomic practices on yield and crop quality must be better understood. Row spacing and population density are implicated in dry matter yield, and therefore, bast fiber production. Four row spacings, four population densities, and two cultivars were examined to determine these effects on dry matter accumulation and bark content. Of all factors evaluated, only row spacing significantly affected dry matter yield. Yield was greatest at the 35.5-cm row spacing, and lowest at the 71- and 101.6-cm row spacings. With regard to bast yield, calculated as a percentage of total sample dry weight, a significant cultivar × row spacing interaction occurred. However, data indicate that manipulating row spacing to maximize total stalk yield per hectare resulted in the highest bast fiber yield for the two cultivars tested. The narrowest row spacing of 35.5 cm, gave the greatest biomass yield as well as the highest bark yield per hectare.     

Specific gravity,dry matter content and starch content of 50 potato cultivars grown under Cyprus conditions

Summary Fifty potato varieties were grown at different geographic areas in Cyprus and were classified into groups according to the specific gravity of their tubers. Specific gravity varied from location to location; it was high at Athalassa, low at Xylophagou, and intermediate in the Paphos and Morphou areas. Specific gravity increased with maturity and significant differences were observed between lifting dates 3 weeks apart; the rate of increase in specific gravity was higher in medium-late than in early varieties. Specific gravity values obtained by the potato hydrometer method were converted into dry matter (DM) and into starch content by standard formulae and a conversion table was prepared and is presented for reference.

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Zusammenfassung Fünfzig Kartoffelsorten wurden in 4 geographischen Gebieten auf Zypern (Abb. 1) getestet und entsprechend dem Spezifischen Gewicht ihrer Knollen in vier Gruppen eingeteilt (Tabelle 1). Das Spez. Gewicht schwankte von 1.0669 (17.62% Trockensubstanz) bis 1.0850 (21.62% Trockensubstanz); die erhaltenen Werter für das Spez. Gewicht wurden mittels Standardformeln in % St?rkegehalt und % Trockensubstanzgehalt umgerechnet. Das spez. Gewicht schwankte von Ort zu Ort und war am h?chsten in Althalassa (eine sp?te Kartoffellage). Für die festgestellten Unterschiede im Spez. Gewicht waren mikroklimatische und Bodenfaktoren in diesen Gebieten verantwortlich (Tabellen 2–4). Unterschiede zwischen den Orten waren stets unabh?ngig von Sorte und Jahreszeit. Das Spez. Gewicht nahm mit der Reife zu, und es wurden signifikante Unterschiede zwischen Ernten, die 3 Wochen auseinanderlagen. festgestellt. Das Mass der Zunahme an Spez. Gewicht war bei mittelsp?ten und sp?ten Sorten, z.B. Arran Banner. Up-to-Date, Cardinal und Maris Piper, gr?sser als bei frühen Sorten, z.B. Premiere und Spunta (Tabelle 5). Zur Erleichterung der Information und der Verwendung der von Simmonds (1977) vorgeschlagenen Formeln wurde eine Tabelle zur Umrechnung der Spez. Gewichtswerte innerhalb des Bereichs von 1.0600 bis 1.1090 in % Trockensubstanz und % St?rke vorbereitet (Tabelle 6).

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Résumé Cinquante variétés de pommes de terre ont été testées dans quatre régions de l'lle de Chypre (figure 1) et ont été classées en 4 groupes selon le poids spécifique de leurs tubercules (tableau 1). La valeur du poids spécifique est répartie entre 1,0669 (17.62% de matière sèche) et 1,0850 (21,62% M.S.); les valeurs obtenues ont été converties en pourcentage d'amidon et en pourcentage de matière sèche (tableau 1) par l'emploi d'une formule standard. Le poids spécifique a varié d'une région à l'autre et a été le plus élevé en Athalassa (localité à pommes de terre tardives). Les facteurs climatiques (micro-climats) et le type de sol de ces diverses régions ont été responsables des différences de valeur de poids spécifique observées (tableaux 2–4); ces dernières ne dépendant ni de la variété, ni de la saison. Le poids spécifique a augmenté avec la maturité des pommes de terre et des différences significatives ont été observées entre des récoltes faites à 3 semaines d'intervalle. Il a été plus élevé chez les variétés demi-hatives et tardives telles que Arran Banner, Up-to-Date, Cardinal et Maris Piper que chez les variétés hatives telles que Première et Spunta (tableau 5). Pour faciliter l'emploi de la formule proposée par Simmonds (1977) une table de conversion des valeurs de poids spécifique (entre les classes de 1,060–1,100) et les pourcentages de matière sèche et d'amidon a été réalisée (tableau 6).

     

The relation between specific gravity and dry matter content of potato tubers

The theoretical basis of the relationship between the percentage of dry matter in a potato and its specific gravity is examined. The relationship is hyperbolic but, for values of dry matter percentage usually encountered with potatoes, a linear approximation is adequate. However the specific gravity of a tuber depends not only on the percentage of dry matter in it but also on the density of the dry matter and the percentage of air in the tissue. Thus dry matter percentages estimated from specific gravities may be in error if it is assumed that the linear approximation is constant.     

The effect of harvest date and tuber-borne sclerotia on the severity ofRhizoctonia disease of potato

Experiments performed in 1976 and 1977 examined the effect of harvest date on the development of tuber-borne sclerotia and the effect of these sclerotia onRhizoctonia disease severity of potato. Results from tubers harvested at seven weekly intervals in 1975 indicate maximum sclerotial development occurred 3–4 weeks after vine killing. When these tubers were planted the following year, few differences occurred in disease severity of stems and stolons with respect to prior harvest date. However, the tubers which had remained in the ground 4–7 weeks after vine killing in 1975 produced the largest and greatest number of sclerotia on progeny tubers harvested in 1976. Experiments in 1976 and 1977 demonstrated that tubers with approximately 20% sclerotial coverage produced stems and stolons with significantly more severeRhizoctonia disease compared to tubers with no visible sclerotia. Sclerotial coverage on tubers of less than 20% did not significantly increase disease severity.     

Influence of Colorado potato beetle sample counts and plant defoliation on potato tuber production

Field experiments were designed to subject Superior potato plants to various levels of defoliation by the Colorado potato beetle (CPB)Leptinotarsa decemlineata (Say), Coleoptera: Chrysomelidae. Defoliation occurred during each of five consecutive plant growth periods and CPB population, plant leaf area, and tuber weight data were recorded for each period. A visual defoliation rating scheme provided an accurate estimate of actual potato plant leaf area of defoliated plants. Data generated from regression analysis demonstrated a significant dependence of leaf area on CPB numbers per plant during some plant growth periods, but numbers of CPB accounted for very little of the total variation in tuber weight. Plant leaf area was the most important independent variable in the tuber weight regression model.     

Influence of chilling on potato tuber respiration,sugar, O-dihydroxyphenolic content and membrane permeability

The response of four potato cultivars to various temperatures was evaluated in respect to respiration, sugar and phenolic content, and ion leakage from cut tissue sections. Respiration decreased with decreasing temperature from 20° to 0°C but after 24 hours at 0°C began to increase and reached a maximum after 10 days at 0°C, then drifted downward. No distinct break in an Arrhenius plot of the respiration data from 20° to 0°C was observed. Reducing and non-reducing sugars did not change initially between 20° and 0°C and did not increase until after 6 or 7 days at 0°C. The magnitude of the increase in sugars varied between cultivars. Only one cultivar significantly increased in phenolic content during chilling. Ion leakage remained constant from 20° to 0°C then showed a transient increase within 24 hours at 0°C. A sustained increase in leakage did not occur until after 10 days at 0°C. Cultivars varied in the rate and magnitude of the increase. The respiratory rise could not be attributed to an increase in sugar content or an increase in membrane permeability. Also, the initial increase in sugars preceded the sustained increase in ion leakage. Differences observed between cultivars in the parameters measured were not considered sufficient to explain differences in chilling sensitivity.     

Sowing date, harvest date and the yield of forage brassica crops

The effect of sowing date, within the period from late May to mid-August, on the DM yield of five leafy forage brassica crops sown to a stand was examined over the period 1976–78. Kale was the crop most sensitive to variation in sowing date and yields declined progressively with later sowings. There was no yield benefit from sowing rapes or stubble turnips earlier than mid- to late-June. Raphanobrassica produced yields as good as rape when sown in June. In 1978, DM yields of rape, kale and Raphanobrassica increased from September to early November, largely as a result of stem growth; kale was slower to accumulate DM than rape in late summer but continued growing longer into the autumn. The DM concentrations of all crops increased from September to December. Rape had a higher DM concentration than stubble turnip. Raphanobrassica was 10–25 g kg^-1 lower in DM concentration than rape or kale. Raphanobrassica produced 23–59% flowering plants from late-May to early-June sowing. Harvest date affected DM yield and concentration, leaf: stem ratio and flowering percentage. The effects of sowing dale on DM concentration were small.     

Some problems in the analysis of pectin in potato tuber tissue

Summary Simultaneous determination of the degree of esterification and pectin content, without extraction, by Cu²⁺ ion exchange is described. The method, based on the high affinity of Cu²⁺ for pectic carboxylic acid groups, is applied to potato tuber tissue and potato, tuber cell wall material, and the results are compared with a combination of pectolytic extraction for pectin content and methanol determination after saponification and distillation. Cu²⁺ ion exchange appeared a valuable method for potato cell wall analysis. During analysis of potato tissue phosphate covalently bound to starch interferes in ion-exchange and leads to erroneous results. A means of correction is given for interference of neutral sugars in the carbazole test after pectolytic extraction of pectic substances.

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Zusammenfassung Eine Ionen-Austauschmethode, basierend auf dem Austausch von Cu²⁺-Ionen mit den S?uregruppen des Pektins, wurde im Hinblick auf die des Pektins untersucht. Diese neue Methode wurde mit der pektolytische Extraktion von pektinischen Substanzen für den Pektingehalt, verbunden mit der Methanol-Bestimmung nach Verseifung und Destillation für den VG von Pektin, verglichen. Beide Methoden wurden bei Kartoffelknollengewebe angewendet. Cu²⁺-Ionen-Austausch ergab h?here Pektingehalte und niedrige VG als die pektolytische Extraktion /Methanol-Analyse (Tabelle 2). Isolierung des Pektins aus Kartoffelgewege in relativ gereinigter Form, z.B. aus den Zellw?nden, und Anwendung beider Analysenmethoden, führten zu einer besseren übereinstimmung des Pektingehaltes und des VG (Tabelle 3). Es wurden einige Anhaltspunkte dafür gefunden, dass Phosphate, die kovalent an die Kartoffelst?rke, die bei der Zellwandpr?parierung entfernt wird, gebunden sind, beim Cu²⁺-Ionen-Austausch st?rend wirken. Für die Analyse von Pektin in den Zellw?nden der Kartoffel scheint sich der Cu²⁺-Ionen-Austausch als eine brauchbare Methode zu erweisen. Die pektolytische Extraktion/ Methanol-Analyse brachte befriedigende Ergebnisse für den Pektingehalt und VG von Kartoffelknollengewebe (Tabellen 2 und 3). Nach der pektolytische Extraktion von Pektinsubstanzen aus Kartoffelknollengewebe wurde die Modifikation der Carbazolreaktion nach Rouse und Atkins zur Bestimmung von Pektin als wasserfreie Galakturons?ure angewendet. Die Korrektur der erhaltenen Werte mittels eines neutralen Zuckertestes (Phenol-Schwefels?uretest) trug zu einer besseren Bestimmung des Pektingehaltes im Kartoffelknollengewebe (und in den Zellw?nden der Kartoffel) bei. Ohne diese Korrektur würde der Pektingehalt um zirka 20% übersch?tzt.

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Résumé Les auteurs ont fait des recherches sur une méthode d'échange ionique, basée sur l'échange de i'ion Cu²⁺ avec les groupes d'acide pectinocarboxylique, dans la détermination dans le tissu de tubercule de pomme de terre, à la fois de la teneur en pectine, et de son degré d'estérification (=DE) sans extraction du complexe pectine. Les auteurs ont comparé la nouvelle méthode avec l'extraction des substances pectiques pour ce qui concerne la teneur en pectine, en combinaison avec leurs déterminations au méthanol après saponification et distillation pour ce qui concerne l'ester de pectine (DE). Les deux méthodes furent appliquées au tissu de tubercule de pomme de terre. La méthode de l'échange d'ion Cu²⁺ donne des teneurs plus élevées en pectine, et plus basses en ester de pectine, que l'analyse ‘extraction pectolytique/méthanol’ (tableau 2). L'isolement, dans les échantillons de tissu de pomme de terre, de la pectine dans une forme déjà relativement purifiée, comme dans les parois cellulaires, et l'application des deux méthodes d'analyse ont conduit à une meilleure estimation aussi bien de la teneur en pectine que de DE (Tableau 3). Les auteurs ont recueilli des preuves que le phosphate est combiné par ses valences à la fécule de pomme de terre qui est enlevée au cours du traitement de la paroi cellulaire, et qu'il interfère dans l'échange d'ion Cu²⁺. L'échange d'ion Cu²⁺ se révèle une méthode pleinement utile pour l'ane lyse de la pectine de la paroi cellulaire de la pomme de terre. La méthode ‘extraction pectolytique/méthanol’ donne des résultats satisfaisants pour l'analyse de la pectine et de DE du tissu de tubercule de pomme de terre (tableaux 2 et 3). Après extraction pectolytique des substances pectiques des tissus de tubercules de pomme de terre, on utilise la réaction du carbazole, modifiée par Rouse et Atkins pour déterminer la pectine sous forme d'acide anhydrogalacturonique. La correction des valeurs obtenues par un test de sucre neutre (test à l'acide phénol-sulfurique) contribue à une meilleure détermination de la teneur en pectine du tissu de tubercule de pomme de terre (et de la paroi cellulaire de pomme de terre). Sans cette correction la teneur en pectine serait surestimée de 20% environ.