Effects of soil-borneRhizoctonia solani Kühn on yield and quality of ten potato cultivars

Summary The effects of soil-borneRhizoctonia solani on yield and quality of potato were studied by an extensive individual plant sampling procedure. From 1983 to 1986, stem canker and stolon pruning were examined in 10 768 plants growing on a sandy soil. Tuber yield and quality and haulm yield per plant were also recorded. The degree of attack byR. solani depended on the cropping frequency of potato. Severe and very severe stem and stolon attacks decreased fresh yield, dry matter yield and dry matter content of tubers and increased the number of deformed and small tubers, whereas the effect on haulm yield and stem number was small. Potato cultivars differed in susceptibility toR. solani, but yield response did not differ significantly between cultivars at the same levels of stem and stolon infection.     

The influence of leaf area,light interception and season on potato growth and yield

Summary Light interception in the photosynthetically active radiation (PAR) range (400 700 nm) was measured over two years in potato crop canopies. Light interception increased linearly with increasing leaf area index (L) up to values of 2.25, light interception increased at a decreasing rate until L=4.0 was attained when around 95% of the incoming radiation was intercepted. The equation I_l=I_oe^kl accounted for 92% of the variance in the relationship between light interception and L, where I_l is the irradiance on a horizontal plane below a leaf area index of L., and k (light extinction co-efficient)=0.335+0.151 (L) 0.0129 (L)². Crop growth rate was found to be linearly related to the PAR intercepted by the canopy in 1980, in the absence of any apparent water-stress. The photosynthetic conversion efficiency of the canopy (g dry weight MJⁱ PAR intercepted) was 3.42 and 2.49 for 1980 and 1979, respectively. Tuber yields were also found to be linearly related to PAR intercepted by the canopy over the whole season.

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Zusammenfassung In den Jahren 1979 und 1980 wurde die Lichtaufnahme der photosynthetisch aktiven Strahlung (PAR) im Bereich von 400–700 nm in Kartoffelbest?nden im Vereinigten K?nigreich gemessen. Die meteorologischen Daten zeigten, dass der Niederschlag in den Jahren sehr unterschiedlich war (Abb. 2); 1979 war überwiegend trocken, vor allem in der sp?teren Vegetationszeit, w?hrend 1980 allgemein ein nasses Jahr war. Die Lichtaufnahme stieg linear mit dem zunehmenden Blattfl?chenindex (L) bis zu L=2,25 an (wobei rund 73% der einfallenden Strahlung aufgenommen wurde) und über L=2,25 nahm die Lichtaufnahme mit einer abnehmenden Rate bis zu L=4,0 zu, wobei rund 95% der einfallenden Strahlung aufgenommen wurden (Abb. 3). Die Gleichung I_L=I_oe^kL gilt für 92% der Varianz in der Beziehung zwischen Lichtaufnahme und Blattfl?chenindex (L), wobei I_L=Strahlung auf einer horizontalen Fl?che unter einem Blattfl?chenindex von L und k (Lichtextinktionskoeffizient)=0,335+0,151(L)−0,0129(L)². Wenn die Konstante k (=0,72) verwendet wurde (Abb. 3) entsprach die Varianz für das ausgew?hlte Modell 88%. Zwischen dem Gesamttrockengewicht (TDW) und der PAR, die aufgenommen wurde, bestand in beiden Jahren ein signifikantes lineares Verh?ltnis. Abb. 4 zeigt die Daten für 1980. Durch den Nullpunkt geführt ergibt sich ein TDW=3,42 (PAR) und 2,49 (PAR) für 1980 bzw. 1979, das bedeutet, dass die Umwandlung von Lichtenergie in Trockensubstanz ohne ersichtlichen Wassermangel 1980 wirkungsvoller war. Abb. 5 zeigt die photosynthetische Wirksamkeit (g Trockengewicht MJ^l PAR) w?hrend der Vegetationszeiten zusammen mit den ?nderungen im Blattfl?chenindex L. Die Wachstumsrate des Bestandes stand 1980 in einem linearen Verh?ltnis zu der von den Bl?ttern aufgenommenen PAR, w?hrend sich für 1979, wo der Bestand stark unter Trockenheit litt, eine Abweichung ergab (Abb. 6). Obwohl w?hrend der beiden Jahre die photosynthetische Wirksamkeit (g Knollentrockengewicht MJ^l PAR, aufgenommen w?hrend der gesamten Vegetationszeit) für das Knollengewicht unterschiedlich war: Knollentrockengewicht=1,97 (PAR) und 2,37 (PAR) für 1979 bzw. 1980, zeigen die Daten, dass ein gesteigertes Wachstum entsprechend einer h?heren Lichtaufnahme zu h?heren Knollenertr?gen führt, unabh?ngig von einer Reihe ackerbaulicher Massnahmen.

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Résumé L'interception des radiations actives pour la photosynthèse (PAR), dans des longueurs d'onde de 400 à 700 nm, est mesurée durant très différente les deux années; 1979 fut particulièrement sec, surtout en fin de saison, alors que 1980 fut une année humide. La quantité de lumière interceptée, augmente linéairement avec l'index de surface foliaire (leaf area index) jusqu'à une valeur de L=4,25 (correspondant à 73% de radiations interceptées) et pour des valeurs supérieures, l'interception augmente à une vitesse décroissante jusqu'à L=4,0 correspondant à 95% de radiations captées (fig. 3). La relation I_L=I_oe^kL interpréte 92% de la variation dans la liaison entre la lumière interceptée et l'index de surface foliaire (L), où I_L est le rayonnement atteignant un plan horizontal situé sous un index foliaire L et K (coefficient d'extinction lumineuse)=0,335+0,151(L) −0,0129(L)². Si on fixe k à 0,72 (fig. 3), la part de variation expliquée par le modèle est de 88%. Une relation linéaire significative entre la matière sèche totale (TDW) cumulée et le PAR intercepté cumulé, a été établie pour les deux années et les données de 1980 sont portées dans la figure 4. Si on fait passer la régression par l'origine, on écrira pour 1979: TDW=2,49× deux années, 1979 et 1980, dans des cultures de pomme de terre du Royaume-Uni. Selon les données météorologiques, la pluviométrie fut et pour 1980: TDW=3,42×PAR. Ces relations indiquent que la conversion de lumière en matière sèche a été plus efficace en 1980 en l'absence de déficit hydrique. L'efficacité de la conversion photosynthétique (g de matière sèche/PAR intercepté) au cours de la saison, est indiquée avec les variations de L dans la figure 5. La vitesse de croissance de la culture est liée linéairement au PAR capté par la végétation en 1980, alors que cette liaison s'écarte de la linéarité en 1979, lorsque la culture est affectée par la sécheresse (fig. 6). Bien que l'efficacité de la conversion photosynthétique (g de poids sec de tubercule/PAR captée durant toute la saison) pour le poids de tubercules soit légèrement différente pour les deux années (en 1979 elle est égale à 2,37 (PAR), en 1980 elle est égale à 1,97 (PAR)). Les données indiquent que l'augmentation de la croissance de la récolte totale, expliquée par l'augmentation de la lumière captée, résultent également du rendement de plus en plus grand des tubercules (fig. 7), sur une série de traitements agronomiques.

     

Physiological effects of calonyctin on development and yield of potato

Summary Foliar sprays of calonyctin, a natural plant growth regulator extracted from the leaves ofCalonyction aculeatum (L.) House, at a concentration 0.05 activity units, increased the tuber yield of six potato (Solanum tuberosum L.) cultivars by 7–19% (mean 15%) during 1993 and 1994. Physiological differences between calonyctin-treated and untreated potato plants were usually detected 30–40 days after spraying them with calonyctin. The chlorophyll content of treated potato leaves increased, and the chlorophyll a:b ratio decreased. By 40 days after treatment the root oxidizability and soluble protein contents of different parts of the plants also increased. Their subsequent decline as the plants aged was inhibited by calonyctin. It is concluded that calonyctin delayed the senescence of potato plants and increased tuber growth at later stages of development.     

Tuberization in potato at high temperatures: Responses to exogenous gibberellin,cytokinin and ethylene

Summary In potato (Solanum tuberosum L., cv. Sebago), benzyladenine (BA) promoted tuberization at high day/night temperatures (32°/18°C), while gibberrellic acid (GA) and chlorethylphosphonic acid (CEPA) reduced tuberization at low day/night temperatures (22°/18°C). These results are consistent with the hypothesis that temperature exerts its influence on tuber formation by altering the balance between endogenous gibberellins, cytokinins and inhibitors, but not ethylene.     

Influence of irrigation regimes on growth and yield of potato cv. Spunta

Summary The effect of furrow and drip irrigation giving 0, 33, 66, 100 and 133% of the maximum evapotranspiration (ETM) was studied on leaf transpiration, stomatal resistance, tuber growth, yield and yield response of cv. Spunta. The research was carried out in Sicily in 1988 and 1989 on early potato crops grown during the winter/spring cycle. Increased water supply increased leaf transpiration, plant fresh weight, tuber growth rate, yield and earliness, and decreased stomatal resistance and tuber dry weight. A higher yield response was obtained at the lower water regimes (ETM of 33 and 66%). There were no significant differences between the two methods of irrigation.     

Field performance of potato minitubers with different fresh weights and conventional seed tubers: Multiplication factors and progeny yield variation

Summary Multiplication factors and progeny yield variation in crops from minitubers of five weight classes (ranging from 0.13–0.25 g to 2.00–3.99 g) and conventional seed tubers were studied in field experiments in three years. Multiplication factors were calculated as the number and weight of progeny tubers produced per planted tuber or per unit planted tuber weight. They were lower for the lighter minitubers when calculated per tuber and higher when calculated per weight. Yield variation was described by coefficients of variation for the number and weight of progeny tubers produced. Variation over individual plants of a crop was higher in stands from the lighter minitubers. Variation over plots within a field was sometimes higher for the lighter minitubers, but variation over years was similar for all minituber classes. Variation over plots in progeny tuber weight was higher for minitubers than for conventional tubers.     

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 effect of irrigation strategies during tuber initiation on marketable yield and development of common scab disease of potato in Russet Burbank in Tasmania

Summary Management of soil moisture deficit during tuber initiation and early development was important for the optimisation of net and marketable tuber yields of cv. Russet Burbank on the typical red ferrosol cropping soils of Northern Tasmania, Australia. An effect of reduced water input during the tuber initiation period on increasing incidence of common scab disease was noted in one trial. In subsequent trials disease inoculum levels were not sufficient to show differences between treatments despite a history of disease at the site. For optimisation of marketable yield and probable assistance in the management of common scab disease it is recommended that irrigation scheduling to known soil moisture deficits be adopted during this period of growth on this soil type.     

Influence of cultivar, season, explant type and seaweed concentrate on potato plantlet quality

Summary The addition of a seaweed concentrate to tissue culture medium improved the quality of potato plantlets. Season, cultivar and explant type affected the most beneficial concentration applied. Concentrations higher or lower than the optimum were less beneficial or adverse to plantlet quality. Terminal buds were more sensitive to non-optimum seaweed application than axillary buds. Decreased water loss from plantlets was one of the potential benefits of seaweed concentrate in vitro, thus improving establishment after transplanting.     

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.     

Effect of soil solarisation and mouldboard ploughing on black dot of potato, caused byColletotrichum coccodes

Summary Preplant soil solarisation and mouldboard ploughing to a depth of 30 and 60 cm respectively were evaluated in two field experiments for the control ofColletotrichum coccodes causing black dot of potato. Solarisation reduced disease incidence by 45% when tarping was done for eight weeks and temperatures reached 56°C in the top 5 cm of soil. With a six week tarping period and lower maximum temperature (50°C) the reduction in disease was a nori-significant 25%. Mouldboard ploughing to a depth of 30 cm reduced black dot by 34% and was twice as effective as ploughing to a depth of 60 cm.     

Effect and interaction of crop management factors on the glycoalkaloid concentration of potato tubers

Summary Potato tuber glycoalkaloid content was measured in response to nitrogen fertilizer rate, storage temperature, length of storage period and cultivar. Cvs Gemchip, Norchip and Russet Burbank were grown with applied nitrogen fertilizer rates of 0, 168 or 336 kg/ha and then stored at either 4.4 or 10°C. Total glycoalkaloid content was determined one month before harvest, at harvest, after three months of storage and after nine months of storage. Higher rates of nitrogen, higher storage temperature and a period of storage all resulted in significantly (P<0.05) higher concentration of glycoalkaloids. The cv Norchip had higher glycoalkaloids than cvs Gemchip or Russet Burbank. Only the storage period had more influence than the environment (difference between years). Significant (P<0.05) two-way interactions were detected for year x cultivar, year x nitrogen, storage period x cultivar and nitrogen x cultivar. Most interactions were due to the unique responses of cultivars.     

Influence of ambient forced-air ventilation rate on potato storage wastage

Summary Potatoes were stored in three insulated bins having ventilation rates of 0.0190, 0.0306 and 0.0417 m³/s·t. The results showed that in the climate of northern Italy potatoes can be stored successfully at ventilation rates of not less than 0.0306 m³/s·t resulting in product weight loss of less than 2.0% after 100 days' storage. The incidence of diseases and of sprouting was very low at rates of 0.0306 and 0.0417 m³/s·t, but greater at 0.019 m³/s·t because of the higher tuber temperature. Laboratory tests simulating ambient conditions confirmed the validity of a thermodynamic model simulating air-potato heat exchange.     

Field performance of potato minitubers with different fresh weights and conventional seed tubers: Crop establishment and yield formation

Summary Field performance of five fresh weight classes of minitubers ranging from 0.13–0.25 g to 2.00–3.99 g and conventional seed tubers was studied in a short growing season (79 or 82 days) in two years. The heavier minitubers gave a more regular emergence, faster ground cover soon after emergence, higher dry-matter yields, and higher fresh tuber yields. Radiation conversion coefficient (RCC) did not differ. Higher tuber yields resulted from more radiation intercepted due to a faster ground cover, and a higher harvest index. All minitubers produced plants with one primary stem. In one experiment when heavier minitubers had long sprouts, time to 50% emergence decreased with tuber weight, whereas dry-matter concentration of progeny tubers increased. Conventional tubers appeared superior to minitubers in all characteristics mentioned except RCC, which was similar. Differences in performance between minitubers and conventional tubers were attributed to weight and age of seed tubers, presprouting method and crop husbandry.     

Relationships between ground cover,intercepted solar radiation,leaf area index and infrared reflectance of potato crops

Summary In field trials with potato several methods determining the proportion of intercepted solar radiation by the crop were compared. Non-destructive measurement of the proportion of ground cover with the aid of a grid correlated well with the proportion of intercepted photosynthetically active radiation as measured with a tube solarimeter and with the leaf area index. Measurement of the infrared reflectance of the crop proved to be an efficient and objective method to show differences between treatments. Moreover, it showed a good correlation with ground cover and radiation interception until full closure of the canopy. Percentage ground cover is useful for assessing intercepted solar radiation and leads to fewer errors in calculation of efficiency of conversion into dry matter than the other methods.     

Effect of planting date and inoculum level on incidence and severity of powdery scab on potato

Summary Powdery scab incidence and severity was examined on six potato cultivars planted at two different dates in a naturally infested field. There were two sub-plots; one where seed was exposed prior to planting to spores ofSpongospora subterranea from scabby peels, which were then added to the furrow at planting, and another where seed was exposed only to natural inoculum within the field. The later planting data reduced incidence and severity, but there were no differences between sub-plots. All cultivars became infected, but ‘Rosa’ was the most susceptible and ‘Katahdin’ the most resistant. Contribution No. 1720, Department of Plant Pathology, The Pennsylvania Agricultural Experiment Station. Authorized for publication September 22, 1988 as Journal Series Paper No. 8007.     

The effect of a seaweed concentrate on the in vitro growth and acclimatization of potato plantlets

Summary The seaweed concentrate ‘Kelpak’ is used commercially in the greenhouse and field to improve plant quality. ‘Kelpak’ was added to the in vitro culture medium of potato cv. ‘BP1’ and also applied as a leaf/soil drench immediately after transplanting. The addition of 0.25% seaweed concentrate to the medium improved plantlet quality and led to better establishment in the greenhouse. No beneficial effect of seaweed concentrate in the tissue culture medium was observed if a second cutting was part of the micropropagation process. Additional application of 0.5% seaweed concentrate in the greenhouse to plantlet cuttings derived from tissue culture was not beneficial.     

Effects of soil characteristics on the relationship between potato cyst nematodes and yield. II. Acidity (soil pH)

Summary The sandy and sandy peat soils of the northeast of The Netherlands are mineralogically very poor and acid. Independently of potato cyst nematode infestations, there is a considerable negative effect of increasing soil pH on potato tuber yield. Potato cyst nematode infections aggravate the effect of soil pH in depressing yield. It was shown that both potato cyst nematode infection and increasing soil pH values reduce the buffering capacity of the root system. Testing for yield as well as for tolerance to potato cyst nematode infection should be made at a range of soil pH values, similar to those found in the target area. This refers to active breeding programmes as well as to the selection of cultivars for yield trials.     

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.     

Potato production from true potato seed (TPS) in Egypt: Effect of the growing season on seedling development,recovery from transplanting and yield

Summary Ware potatoes were produced from true potato seed by transplanting seedlings to the field in different growing periods to evaluate environmental constraints of this production method in the Nile delta. In the autumn season, with high temperatures and long-day conditions during seedling culture in the nursery and transplant establishment in the field, seedling development was fast, and transplants resumed growth within 5 days of transplanting in the field. Tuber yields ranged between 120 and 160 dt ha⁻¹. In the spring season, with low temperatures and short-day conditions during the initial growing phase, seedling development in the nursery was slow and biomass partitioning between above ground organs (stems, leaves) and tubers was shifted towards the tubers. This partitioning was further enhanced by transplanting the seedlings in the field. Seedlings recovered only slowly from transplanting or died. It is concluded that potato production via transplants is poor in the spring season when premature tuberization of seedlings in the nursery leads to slow field establishment and low tuber yield.