The effect of chloride fertilization on blackspot susceptibility and other quality characteristics and on yield of potato

Summary Trials were carried out in two years on a sandy loam and on a heavy clay soil with two cultivars to examine the potential of chloride fertilization as a tool to reduce blackspot susceptibility of potatoes and to investigate other effects on yield and quality. Blackspot susceptibility was significantly reduced in cv. Marijke, but not in cv. Bintje as a result of increasing doses of applied chloride from 0 to 400 kg ha1. Dry matter concentration, assessed as under-water weight, was reduced by chloride in both cultivars at the two locations. Fry colour of French fries was improved by chloride. Applying 400 kg ha⁻¹ Cl⁻ to both soil types decreased net tuber yield >35 mm of cv. Bintje but not of cv. Marijke. Chloride caused slower emergence, retarded crop development and less stems per plant on the sandy loam soil but not on the heavy clay soil.     

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.     

The effect of some environmental factors on potato tuber numbers

Summary Five experiments studied the effects of shading, temperature and stolon growth medium on stolon and tuber formation. The lowest numbers of stolons and tubers were produced at the higher and lower nodes. Numbers of primary stolons and tubers were relatively stable across nodes and treatments and variation in total numbers was largely due to changes in numbers of lateral and branch stolons. In the field, 70% shading reduced numbers of stolons and tubers by reducing lateral and branch stolons, while in hydroponics, 45% shading and temperatures at initiation had no effect on tuber numbers. In both environments later planting tended to reduce numbers of stolons and tubers. There were large effects of the physical environment, with compost producing three times as many tubers as dry vermiculite. The potential number of tubers may be determined by the number of stolons and the environmental conditions affecting stolon formation and development.     

The effectiveness of using a minituber crop for selection of agronomic characters in potato breeding programmes

Summary Performance of 20 potato genotypes was studied for seven agronomic characters in crops raised from minitubers and normal seed tubers. Correlation coefficients were computed between minituber crop and normal seed crop in order to study the selection efficiency at minituber crop level. The performance of normal seed crop was significantly better than the minituber crop for various characters including tuber yield and its components. Correlation coefficients between minituber and normal seed crop were significant for various characters except number of stems and number of tubers. Highest correlation coefficient (r=0.86) was for tuber yield followed by average tuber weight (r=0.67) and number of nodes (r=0.63). The results suggest that selection for tuber yield can be practised at the minituber crop level in potato breeding programmes     

The effect of irrigation and nitrogen on powdery scab and yield of potatoes

Summary Powdery scab, caused by the fungusSpongospora subterranea, has developed in the Cappodocia region of Turkey because of changes in agronomic practices, such as excessive irrigation and nitrogen fertilizer use and growth of highly susceptible cultivars. The most suitable irrigation and nitrogen application levels were established to maintain powdery scab at minimum levels without affecting potato yield. Three irrigation levels were used in 1998 (673, 897, 1121 mm) and five in 1999 (329, 494, 658, 823, 987 mm). Nitrogen levels were applied 150, 300, 450, 600 kg N ha⁻¹. In 1998, least powdery scab occurred with 673 mm irrigation, which yielded 41 t ha⁻¹ potatoes. The lowest disease severity occurred in 1999 with 494 mm irrigation and 150 kg N ha⁻¹. At these levels, tuber yield was 34 t ha⁻¹ which was not significantly different from the highest yield measured. In 1999 and at two of the three irrigation levels inl998, nitrogen increased disease severity.     

The impact of some agronomic factors on the variability of potato tuber size distribution

Summary Using data from a wide range of experiments, the effects of some agronomic factors on the variability of the tuber size distribution were calculated. The factors studied were nitrogen (N), phosphorus (P), potassium (K), seed-tuber planting density, physiological age, date of harvest, seed-tuber weight, irrigation, cultivar and site of production. There were significant effects of N, date of harvest, cultivar and site of production on the variability of the tuber size distribution measured as the coefficient of variation (CV) of tuber size. The CV increased with higher levels of aplied N and with later harvesting. The largest effect, but one that was unquantifiable, was that of site of production. These results demonstrate that the uniformity of tuber size distribution can vary and suggest that work to understand the reasons for this would be valuable.     

Amino acid composition of coagulable protein from tubers of 34 potato varieties and its relationship with protein content

Summary Samples of coagulable protein, from tubers of 34 varieties ofSolanum tuberosum, were analysed for amino acids. The coagulable protein was rich in most of the essential amino acids. The essential amino acid index ranged from 86 to 93. Methionine was the first limiting essential amino acid. Its content in coagulable protein was considerably higher than values reported in literature. Lysine content was very high, which makes the protein a valuable component for mixed feed. Arginine was the second limiting amino acid. The varietal differences in amino acid composition were small. There was no correlation between protein content and content of most of the essential amino acids. Breeding for increased protein content in potato may be expected to have little effect on the nutritional value of the protein. Selection can be directed to content of coagulable protein.

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Zusammenfassung Aus Knollen von 34 Sorten vonSolanum tuberosum mit grossen Unterschieden im Proteingehalt wurden Muster von koagulier-barem Protein hergestellt. Die Proteinmuster wurden auf Aminos?uren analysiert. Methionin und Cystin wurden mittels einer Methode von Moore (1963) (Tabelle 1) getrennt bestimmt. Das koagulierbare Protein weist hohe Gehalte bei den meisten essentiellen Aminos?uren auf (Tabelle 2). Der Index der essentiellen Aminos?uren (EAAI) reichte von 86 bis 93, was für ein Pflanzenprotein hoch ist. Methionin was die erste begrenzende essentielle Aminos?ure (Tabelle 3), aber sein Gehalt war bedeutend h?her als in der Literatur aufgeführt. Der Lysingehalt war sehr hoch, was das Protein zu einem wertvollen Bestandteil für Mischfutter macht. Arginin war die zweite begrenzende Aminos?ure. Zwischen Arginin- und dem Proteingehalt wurde eine signifikant negative Korrelation (r=−0,589) festgestellt. Dies ist wichtig. wenn das Protein im Futter für Geflügel, das einen hohen Argininbedarf hat, verwendet wird. Die sortenbedingten Unterschiede in der Zusammensetzung der Aminos?ure waren relativ klein (Tabelle 2). Es gab keine Korrelation zwischen Proteingehalt und dem Gehalt an den meisten essentiellen Aminos?uren (Tabelle 4). Der Züchtung auf erh?hten Proteingehalt in Kartoffeln wird nur wenig Einfluss auf den N?hrwert des Proteins haben. So kann die Auslese auf den Gehalt an koagulierendem Protein ausgerichtet werden.

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Résumé Dans le but d'étudier les protéines coagulables on a préparé des échantillons avec 34 variétés deSolanum tuberosum ayant de grandes différences dans leur teneur en protéines. A partir de ceux-ci on a effectué l'analyse des acides aminés. La méthionine et la cystine ont été évalués sèparément par la méthode de Moore (1963) (tableau 1). Les protéines coagulables avaient une teneur élevée pour la plupart des acides aminés indispensables (tableau 2). Leur index se situait entre 86 et 93, ce qui est élevé pour des protéines de plantes. La méthionine a été le premier acide aminé indispensable limitant (tableau 3) mais sa teneur était considérablement plus élevée que celle donnée dans la littérature. La teneur en lysine était très haute, faisant de ces protéines un constituant valable pour les aliments composés. L'arginine a été le second acide aminé limitant. Une corrélation négative (r=−0,589) entre l'arginine et le taux de protéines s'est avérée significative. On doit en tenir compte lorsque ces protéines sont utilisées comme aliments destinés aux volailles, qui nécessitent un taux élevé d'arginine. Les différences variétales en acides aminés ont été relativement faibles (tableau 2). Il n'existe pas de corrélation entre la teneur des protéines et la plupart des acides aminés indispensables (tableau 4). L'hybridation dans le but d'augmenter le taux de protéines dans les pommes de terre peut être considéré comme n'ayant que peu d'effet sur la valeur nutritionnelle de ces protéines. Aussi, la sélection peut être orientée vers l'amélioration de la teneur en protéines coagulables.

     

Use of single-leaf cuttings of potato for efficient mass propagation

Summary Potato stock plants of five commercially propagated varieties, which derived from tissue culture, were grown at a low light irradiance in non-aseptic conditions. The plants produced tiny-leaved etiolated stems, which were a good source of cuttings for further propagation. The method was tested by growing micropropagated and cutting propagated plants as three lines of stock plants, based on different clonal generations, and which were repeatedly harvested for cuttings. There was wide variation in the multiplication capacity among the varieties used. The most productive variety produced more cloned potato plants than when micropropagated in vitro. Stock plants derived from single-leaf cuttings produced more new cuttings than when derived from tissue culture. The growing facilities used were simple and inexpensive and could be set up anywhere. The method is economically competitive due to the need of only very simple and inexpensive growing rooms, and would be worth using particularly in developing countries and also in advanced potato production. All the cuttings of different harvests rooted well and the last propagated cuttings of the lines were still free of prevalent viruses although using simple growing facilities.     

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.     

Amylolytic activity in stored potato tubers. 2. The effect of low-temperature storage on the activities of α-and β-amylase and α-glucosidase in potato tubers

Summary Tubers of the potato cultivars Record, Wilja, Pentland Dell and Brodick (formerly clone 137371) were sampled before and after storage at either 4°C or 10°C. Reducing sugar content stayed constant during storage at 10°C in all four cultivars but rose greatly during the first 6–12 weeks of storage at 4°C in Record, Wilja and Pentland Dell but not in Brodick. Amylolytic activity was determined after 5 weeks storage using blockedp-nitrophenyl maltoheptaoside as substrate for α-amylase,p-nitrophenyl maltopentaoside as substrate for β-amylase, andp-nitrophenylglucopyranoside as substrate for α-glucosidase. The values obtained from tubers stored at 4°C were higher than those from tubers stored at 10°C, the differences being much less in Brodick than in the other three cultivars.     

Carbohydrate metabolism during tuber initiation in potato: A transient surge in invertase activity marks the stolon to tuber transition

Summary The relationship between carbohydrate metabolism and tuber initiation in potato was determined by monitoring changes in the amount of starch and sugars along with the activities of sugar metabolizing enzymes upon transfer of plants to tuber-inducing conditions (TI; short days, cold nights) from non-inducing conditions (NTI: long days, warm nights). Switch to TI conditions caused an immediate slow-down in plant growth and triggered swelling of stolon tips, which went on to develop into tubers. Leaves of plants moved to TI conditions accumulated less starch and sugar while their stolon tips showed a sudden upsurge in starch content and a sharp decline in sugars even before any tip swelling was detectable. These changes were paralleled by a transient surge in the activity of cell wall invertase (74%) and soluble invertase (30%) in stolon tips of plants transferred to TI conditions in two unrelated cultivars under different experimental conditions. As the surge in invertase activity faded, it was replaced by a substantial increase in sucrose synthase activity as the tuber enlargement proceeded. The transient increase in invertase activity just prior to tuber initiation appears to mark a turning point in the transition of stolon tip to tuber.     

Characterization of pectic substances from two potato cultivars with different sensitivities to prewarming

Summary Potato cultivars Chieftain and Kennebec were prewarmed at 70°C for 15 min. prior to heating at 100°C for 18 min. in a water bath. Chieftain exhibited a large increase in fracturability upon treatment while Kennebec showed a smaller increase. Pectic substances of the two cultivars were sequentially extracted in water, sodium hexametaphosphate (0.5%), hydrochloric acid (0.05M, 50°C), and sodium hydroxide (0.05M, 5°C). The largest fraction isolated from both cultivars consisted of hydroxide-soluble pectic substances, and was followed by the acid-soluble fraction. Chieftain contained significantly greater amounts of the hydroxide-soluble fraction than Kennebec. Ion exchange chromatography revealed that the extracted pectic substances from the two major fractions consisted of a charged pectin chain with attached neutral sugars. Gel filtration chromatography revealed wide molecular size distributions for the isolated pectic substances. Pectic neutral sugar content for the hydroxide-soluble fraction (50% of total pectic substances) was greater for Chieftain than for Kennebec.     

The resistance of potato plants toErwinia carotovora subsp.atroseptica in relation to their calcium and magnesium content

Summary The effect of adding gypsum (CaSO₄) to growing media on the resistance toErwinia carotovora subsp.atroseptica (van Hall) Dye of potato (Solanum tuberosum L.) stems and mother and daughter tubers was examined in field and glasshouse experiments. The decayin situ of inoculated mother tubers from field plots treated before planting with gypsum was significantly delayed compared with tubers sampled from non-amended plots. Blackleg development was also significantly delayed in the gypsum-amended plots; however, for both mother tubers and stems the increased resistance associated with the application of gypsum later disappeared. Stem resistance tended to be related to tissue calcium and magnesium concentrations which were higher in plots treated with gypsum than in untreated plots. Daughter tubers produced in plots amended with gypsum generally contained a higher concentration of calcium in their cortex and were more resistant to decay byE. carotovora subsp.atroseptica but the effect was not consistent.     

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.     

Yield response of potato genotypes to different soil water regimes in contrasting seasons of a subtropical climate

Summary Potato crops in subtropical climates are often subjected to water stress, resulting in low yields and poor tuber quality. The yield response of potato genotypes to water supply was investigated in six trials, three each in spring and autumn plantings. Trials were conducted under automated rain shelters, using an irrigation boom to impose five soil water regimes. The negative effect of water stress on tuber yield was more detrimental in spring than in autumn, because of higher atmospheric evaporative demand and higher temperatures in spring. An average yield reduction of 68% was recorded for the most severely stressed regime in spring plantings, while the mean reduction for the same treatment in autumn was only 42%. Genotypic differences in yield response to drought were clearly illustrated in spring, but not in autumn. This suggests that the choice of genotypes is only influenced by the availability of water in spring, when more drought tolerant genotypes should be used.     

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 boron on calcium uptake and growth in micropropagated potato plantlets

Summary Boron (B) requirements differ widely among plant species and the concentration range between toxicity and deficiency is less for B than for any other nutrient. Excess B can adversely affect calcium (Ca) uptake and plant growth. Potato cvs Bintje and Norland plantlets were micropropagated on Murashige & Skoog (MS) nutrient medium, supplemented with 3 (MS control level) or 9 mM Ca, and a range of H₃BO₃ levels (0.025 to 0.300 mM B). Medium B levels of 0.100 and 0.300 mM decreased Ca content in leaves and shoots of cv. Norland, but not Bintje. Medium B level of 0.025 mM, which is 25% of the control MS level, enhanced Ca uptake in cv. Norland and did not compromise normal plantlet growth in either cultivar. This lower H₃BO₃ level (0.025 mM B), and a B-free gelling agent such as Gelrite, could be used for micropropagation of potato and possibly other species susceptible to Ca defifiency disorders.     

Assessing progenies of potato for resistance to skin spot (Polyscytalum pustulans) in the glasshouse

Summary Crosses were made between six parents differing in susceptibility to skin spot and glasshouse-grown tubers from true seedlings of the nine resulting progenies assessed for resistance to the disease. The assessment was evaluated by a two-year comparison with the behaviour of field-grown tubers of the progenies and their parents. The correlations between progenies in the glasshouse and field were r=0.911 and 0.753 and those between the mid-parental values and the progeny means were high (r>0.864), indicating that parental differences were heritable. It is concluded that correlations were sufficient for glasshouse-grown tubers to be used for assessing large numbers of progenies in genetical studies and for eliminating highly susceptible progenies at an early stage in a breeding programme. R.L. Wastie died 16.01.96.     

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.