Specific Gravity, Dry Matter Concentration, pH, and Crisp-making Potential of Ethiopian Potato (Solanum tuberosum L.) Cultivars as Influenced by Growing Environment and Length of Storage Under Ambient Conditions

A study was conducted to investigate the influence of genotype, growing environment and storage period on postharvest quality of seven released potato cultivars grown at Adet (2240 masl), Chilga (2270 masl), and Dabat (2620 masl), northwest Ethiopia in 2006. Cured tubers of each cultivar from each location were stored at ambient conditions for 8 weeks in a locally constructed dark room in Adet, the location with the highest temperatures. The quality of the tubers and the crisps prepared from them was evaluated at weekly intervals. Tubers from cvs Jalenie, Guassa, and Zengena had a high specific gravity (1.088–1.094) and dry matter percentage (26.2–27.1%) when grown in Dabat and Chilga, and a lower specific gravity (1.064–1.072) and dry matter percentage (22.3-22.7%) when grown in Adet. These cultivars produced crisps with a taste value of 8 (like very much) when grown in Chilga and Dabat and of almost 7 (like moderately) when grown in Adet. There was a progressive reduction in specific gravity, dry matter percentage, and taste of crisps with increase in storage time. Cultivars with higher dry matter concentration maintained a better quality than cultivars with a lower dry matter concentration. Across growing locations and cultivars, 57% of the crisps samples were white to cream colored, 33.3% light tan and 9.5% dark tan after 1 week of storage, whereas after 6 weeks of storage none of the cultivars produced white cream colored crisps. It is reasonable to conclude that cvs Jalenie, Guassa, and Zengena can produce tubers with a high dry matter percentage under Chilga and Dabat conditions, from which acceptable crisps can be prepared from tubers stored up to 6 weeks under ambient conditions.     

The Effect of Long Term Storage on Bacterial Soft Rot Resistance in Potato

Bacterial soft rot is a serious disease in potato (Solanum tuberosum L.), causing rapid tuber tissue maceration and, consequently, marketable yield loss. Soft rot bacteria, including Pectobacterium carotovorum subsp. carotovorum (Pbc), are favored by moist conditions, which are prevalent in large potato storage facilities. However, although most potatoes in North America are stored before use, there are no published surveys of soft rot resistance in cultivars exposed to long-term storage conditions. Thus, we tested 65 cultivars and 13 breeding lines for soft rot resistance after 6 months of storage. There was a significant effect of cultivar and production environment on soft rot resistance score. During 6 months of storage, tuber soft rot resistance in resistant clones did not change, while it changed in susceptible clones. The three most resistant cultivars to soft rot were Freedom Russet, Anett, and Alaska Red Eye.     

Economic Optimum Nitrogen Fertilization Rates and Nitrogen Fertilization Rate Effects on Tuber Characteristics of Potato Cultivars

The objective of the research was to determine the economic optimum nitrogen (N) fertilization rates and to determine the effects of N fertilization rates on tuber characteristics and fresh mass loss after storage under cold and ambient conditions of four potato cultivars, Ágata, Asterix, Atlantic, and Monalisa. The experiments were, simultaneously, conducted in the same area and similar experimental conditions during the fall/winter period in Viçosa, Minas Gerais State, Brazil. In each experiment, five N fertilization rates (0, 50, 100, 200, 300 kg ha^?1) were evaluated in a randomized complete block design. For all cultivars, increasing N fertilization rate increased total and marketable yields and tuber dry matter yield up to a maximum following a quadratic model. Increasing N fertilization rate linearly increased the tuber protein concentration of Atlantic and Monalisa and had no effect on tuber pH. N fertilization rate effects on tuber mass, tuber titratable acidity, and fresh mass loss during storage were cultivar-dependent. N use efficiency (tuber yield divided by N fertilization rate) decreased with increase in N fertilization rate. The economic optimum N fertilization rates ranged from 147 to 201 kg ha^?1 depending upon cultivar and relative prices of N and potato tubers. Depending on the cultivar, under favorable price conditions (low N price and high tuber price), the economic optimum N fertilization rates to be applied by potato growers were 92–95% of the estimated N fertilization rate for obtaining the maximum potato yield, whereas under unfavorable conditions (high N price and low potato tuber price) the economic optimum N fertilization rates to be applied should be decreased to 86–92% of the rates for maximum yield.     

Chipping performance of three processing potato cultivars during long-term storage at two temperature regimes

Three potato cultivars (Russet Burbank, Norchip, and Gemchip) grown with nitrogen applied at three rates were stored at two temperature regimes (Treatment 1: 13 months at 10 CTreatment 2: 1 month at 10 C; followed by a 1 C decrease per week until tubers were 4 C; followed by 6 months at 4 C; followed by a 1 C increase per week until tubers were 10 C; followed by 3 months at 10 C). Tuber chemical components and potato chip appearance were measured at harvest and after 3, 6, 9, 11, 12, and 13 months; these measurements were performed within 24 hours of the time potatoes were removed from storage. Sugar responses (tuber glucose, fructose, sucrose) and potato chip appearance were affected by cultivar over time in both years and storage temperatures. Russet Burbank tubers displayed a significantly higher glucose forming potential and produced darker appearing chips, regardless of storage temperature or time in storage, compared to Norchip and Gemchip. Potatoes receiving a cold-storage treatment contained less sugar and produced lighter appearing chips after 12 months storage compared to tubers stored at a constant 10 C for 12 months. The linear association between tuber chemical components and potato chip appearance varied with storage temperature.     

The concept and development of management profiles for potato cultivars and selections

Potato (Solanum tuberosum L.) growers in Ontario, Canada have funded research specifically to develop management profiles for potato cultivars. Such profiles have been developed for Atlantic, Conestoga, Jemseg, Monona, Norchip, Shepody, Superior and Yukon Gold grown under Ontario conditions. The development of management profiles to facilitate the optimum production and storage of different potato cultivars and selections is recognized as a valuable tool in aiding in the technology transfer of potato research and information to growers and processors. Unique differences among cultivars such as herbicide tolerance, time and duration of bulking, fertility requirements, processing quality and other variables may have significant impact on management of a particular cultivar. Some cultivar traits can be modified via management techniques while others cannot. A clarification of such information is critical to the industry.     

The use of hormonal and osmotic growth retardants in media used for the storage of potato germplasm in-vitro

Summary Cultures of 23 potato cultivars were examined for their responses to hormonal and osmotic growth inhibitors incorporated in media used for storage in-vitro. Cultivars differed in their tolerance of inhibitors and also in their growth on a Murashige and Skoog medium with 3% sucrose. Both osmotic and hormonal growth retardants restricted the development of shoot tips but there were significant cultivar x treatment interactions, indicating that the ranking of cultivars will vary with the media used. Such interactions may complicate the establishment of facilities for storage in-vitro. However, addition to the basal medium of 5 mg l⁻¹ abscisic acid reduced both the overall mean scores and, more importantly, the between cultivar variance; its use in conjunction with low temperature shows promise as a method for conserving potato germplasm in-vitro.     

Change in Some Glycoalkaloids of Potato under Different Storage Regimes

The potato (Solanum tuberosum L.) is an important food crop worldwide. Potato tubers can be stored to provide continuity of supply between production seasons, but it is important that they be stored under appropriate conditions as incorrect storage will result in deterioration in end user quality and may increase glycoalkaloid levels. We have investigated the effects of types of household storage on potato glycoalkaloid content (total glycoalkaloids [TGA]; α-solanine; α-chaconine) in Turkey. Tubers of potato cultivars (cvs.) Agria and Bettina were stored under four types of storage conditions (indirect sunlight for 10 h per day and dark storage for the remaining 14 h per day; storage under continuous fluorescent light; storage in constant darkness; storage in the dark in a refrigerator) for 56 days. Samples of tubers were taken at the beginning of the storage period and after 14, 28 and 56 days of storage for tuber glycoalkaloid measurement. Tubers stored in the three light environments showed an increase in glycoalkaloid levels; however, none of the cv. Agria tubers reached the critical level of 200 mg/kg tuber. On day 56 the TGA level of cv. Bettina tubers stored under fluorescent light reached 234.31 mg/kg.     

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.     

A bioassay with excised potato shoot-tips for assessing the effect of growth-inhibiting volatile compounds in the potato

Summary A bioassay technique is described for assessing growth-regulatory activities of volatile compounds in the potato. Excised potato shoot-tips (3 mm) were cultured aseptically in an aqueous medium in the dark at 25°C. After 7–12 days in culture, growth rates were measured by the increase in length of the treated shoot-tips. The addition of low concentrations (1 μmol/l) of gibberellic acid (GA₃) and kinetin to the culture medium enhanced shoot growth. Known sprout suppressants inhibited growth of shoots in the bioassay. Of those tested 1,4-dimethylnaphthalene was found to be the most potent. The effectiveness of these known suppressants of sprout growth of whole potato tubers in inhibiting growth in the bioassay is presented as evidence of the validity of using this bioassay to detect unknown growth inhibitory volatile compounds evolved by stored potatoes.     

Breeding progress for potato chip quality in North American cultivars

Forty-four potato cultivars, released in the period between 1876 and the present were grown concurrently in field trials, stored simultaneously in three different environments, then evaluated for chip quality. They represented cultivars historically used and/or bred for potato chip production. Quality factors measured were tuber solids, chip color, reducing sugar levels, sucrose levels, and percent of defect-free chips. Tuber solids tended to increase in the late period cultivars, but trends were erratic. The release of Lenape marked the beginning of an increase in tuber solids that has continued to the present. There was a significant trend for lower reducing sugars and better chip color that corresponded to increasingly later cultivar release dates. Since about 1960, progress toward lower reducing sugars and better chip color has been constant, regardless of whether tubers were stored at 4.4 C, stored at 4.4 C and reconditioned, or stored at 10 C. Late period cultivars tended to have a greater percentage of defect-free chips in comparison to those released earlier, with most of the improvement coming during the last few years. This study provided evidence that potato breeders have made significant progress in developing cultivars with good chip quality. Evidence was also found that Lenape was a landmark cultivar and has been an important contributor to the observed breeding progress     

Regeneration of plantlets from single cells in potatoes

Regeneration of plantlets from isolated single cells of potato tubers can be achieved through several culturing procedures, each maintained on defined medium and under specific environmental conditions. High auxin and high temperature were favorable for cell proliferation while high cytokinin and alternating low temperature promoted embryoid formation and plantlet regeneration.     

Assessment of the physiological vigour of new potato cultivars in Switzerland

Summary Dormancy, incubation periods and physiological vigour or rusticity of new potato cultivars were determined during the official cultivar assessment programme in Switzerland. A total of 60 cultivars were assessed, including the standards, Sirtema (early), Bintje (mid-early) and Eba (mid-late); Russet Burbank was re-examined. Large variation between cultivars was observed, from 2000 to 3400 day-degrees for dormancy and from 1900 to 3700 day-degrees for incubation periods, expressed as sums of cumulated temperatures above zero centigrade. Field trials with physiologically aged seed identified the physiological vigour or rusticity of the cultivars. Those with low vigour or low rusticity showed poor emergence and yield after prolonged sprouting periods. The lowest produced less than 10% of the yield of seed of optimum physiological age stored under standard conditions. However, some high vigour or very rustic cultivars produced 100% of their potential yield. There was no relationship between earliness and physiological vigour. Vigour is very useful to farmers because it indicates those cultivars that are sensitive to warm storage or long sprouting periods and desprouting before planting. Dr Winiger passed away on 9th October 2000     

通过农杆菌介导将菜豆几丁质酶基因导入马铃薯

选用两个生产上主栽马铃薯品种“鲁引 1号”和“鲁引 4号”的试管微型薯为材料 ,通过农杆菌介导成功地将菜豆几丁质酶基因导入到马铃薯中。试管微型薯薯片与农杆菌共培养 3d后 ,转到含卡那霉素 10 0mg/L的分化培养基上诱导不定芽分化。待抗性芽长到 1 0～ 1 5cm高时 ,转入含卡那霉素 10 0mg/L的液体培养基中进行生根筛选。经过分化和生根两轮筛选的转化植株的PCR检测结果均为阳性 ,而未经转化的对照植株为阴性 ,证明该筛选系统是可靠的。早熟品种鲁引 1号的转化频率明显高于晚熟品种克新 4号 ,其最高转化频率为 4 1 0 % ,平均每个外植体可得到 3 85株转化苗。转化植株的抗病性鉴定正在进行中     

The effect of storage conditions on subsequent field performance of potato seed tubers in Tunisia

Summary Seed tubers of four cultivars were grown under similar conditions and harvested simulataneously. They were stored in traditional dark storage, diffused-light storage, or cold storage, and with combinations of these three methods for 150 or 230 days beginning in the hot, dry summer period. The effect of storage conditions on emergence, stem and tuber number, tuber size distribution and yield is discussed. Results suggest an optimal combination of storage method, cultivar choice, and sprout management practices may be achieved to obviate the need for cold storage in warm climates. Emergence and yield were consistently good for the 150-day storage period when traditional storage was followed by diffused-light storage. The sam technology gave promising results for the 230-day period with cultivars Claustar or Désirée when seed was desprouted prior to planting.     

Sugar-Starch Metabolism and Antioxidant Potential in Potato Tubers in Response to Different Antisprouting Agents During Storage

Single applications of different antisprouting agents like hot water treatment, spearmint oil and clove oil were carried out on potato cultivar “Lady Rosetta” to compare their efficacy with that of synthetic chloro isopropyl N-phenyl carbamate (CIPC). The tubers were stored at ambient storage conditions (25?±?2 °C) for 81 days to assess changes in their sugar-starch concentrations and antioxidant potential. Antioxidant potential in the tubers was assessed as their total phenolic concentrations and radical scavenging activities. In addition, the enzymatic activities were also determined in order to evaluate the possible depletion of these antioxidants as substrate during storage. Results revealed significant response of stored potatoes to all antisprouting agents compared with the control (P?≤?0.05). CIPC and clove oil applications maintained tuber dormancy almost twice as long (81 days) as observed in the control (45 days). Application of spearmint oil and hot water treatment maintained tuber dormancy for almost 2 months. However, it was associated with an increased percentage sprouting during the last weeks of storage. At the end of storage, the highest starch (16.83%) and lowest sugar (0.99%) concentrations were estimated after CIPC application and maximum total phenolic concentration (143.57 mg gallic acid equivalent (GAE)/100 g), and highest antioxidant activity (39.73%) were found after clove oil application. Enzymatic activities were not statistically different between CIPC and clove oil application during most of the storage period. Results showed that efficient replacement of CIPC with clove oil in the premium potato cultivar might be useful; this may avert related food safety and environmental issues and would also ensure organic potato storage.     

Production of perennial ryegrass cultivars of different maturity types when grown as pure swards and in certain combinations

A field investigation was carried out over 3 years to determine if there was a synergistic effect on total or seasonal yield when cultivars of perennial ryegrass were grown in combination. The three cultivars used were Stormont Zephyr, Hora and Perma, representing respectively early, medium late and late maturing groups. Each cultivar was grown as a pure stand and also as a 50:50 mixture with each of the other two cultivars. Each of these swards was maintained under two rates of nitrogen fertilization (300 and 600 kg per ha per annum) and under two harvesting treatments (4 and 8 harvests per annum). Mixture yield did not exceed significantly the pure sward yieid of the highest yielding component. Occasional yield improvements were detected for the mixtures averaged as a group over monocultures averaged as a group. There was a tendency, especially under frequent cutting, for the yield response to nitrogen to be greater from mixed than from pure swards.     

Effects of Potato Cultivar on the Components of Nitrogen Use Efficiency

Maximising potato nitrogen use efficiency (NUE) is necessary to combine high yields, market requirements, high economic income and low environmental impact. A 5-year study was conducted to assess the cultivar effect on NUE components in France. Seven trials were carried out in the Beauce, Picardie and Nord-Pas de Calais regions. The protocol combined two factors: cultivar (‘Agata’, ‘Bintje’, ‘Innovator’, ‘Lady Claire’ and ‘Spirit’) and nitrogen application along a complete response curve (six to seven rates). Total tuber yield, 50 mm tuber yield and nitrogen uptake at haulm killing were measured. We demonstrate that the potato cultivar has a clear effect on NUE components. This effect is supported both by nitrogen uptake efficiency (NupE) and by nitrogen utilisation efficiency (NutE). It implies that the potato cultivars tested generate different nitrogen requirements per yield unit to reach the optimum yield. The way to characterise these differences for all cultivars available in registration trials must be considered before taking into account a cultivar effect on NUE in nitrogen recommendations for farmers.     

The relationship between respiration and chip color during long-term storage of potato tubers

Processing potatoes, both sprout inhibited and untreated, were evaluated for respiration rate and chip color during storage under commercial conditions (12 C, approximately 95% relative humidity, in darkness) following three growing seasons. While absolute respiration rates varied depending upon growing season and treatment, all cultivars and treatments studied during the 1995, 1996, and 1997 storage seasons showed similar respiration profiles. The initial stage following curing and sprout inhibition treatment (if applied) showed essentially constant respiration rates for a period of time varying from two to 15 weeks, depending upon growing season, treatment and cultivar. This was followed by a stage that showed a linear increase in respiration rates. In some cases the respiration rates eventually stabilized, or decreased. There was an apparent correlation between respiration trends and chip color changes in most cases, though the statistical significance varied between cultivars and seasons. Qualitative analysis of the data showed that the point at which respiration rates began to increase coincided with the onset of the decline in chip color quality. These trends suggest that measurement of tuber respiration may provide a non-destructive andin situ method to predict changes in processing quality of stored potato tubers.     

Analysis of <Emphasis Type="Italic">Potato Mop-Top Virus</Emphasis> Survival Probability in Post-Harvest Storage

Potato mop top virus (PMTV) induced necrosis can cause tuber quality loss at harvest and storage. Stored potatoes help maintain a constant supply of potatoes to the market and processing industry. PMTV-induced necrosis continues to develop during storage and appropriate timelines are needed for growers to make marketing decisions of their potatoes before incurring any significant quality losses. Survival analysis was used to estimate the time to event occurrence (PMTV-induced necrosis) in four (red-, russet-, white-, and yellow-skinned) potato market types across six post-harvest assessments conducted over two years. At each assessment the presence and absence of PMTV-induced necrosis was recorded and probability of tuber survival was estimated. Survival curves were significantly different among the four market type potato cultivars (Log-Rank test, P < 0.0005). Red- and russet-market type cultivars showed low and high survival probability, respectively, demonstrating that red cultivars need priority marketing. The survival probabilities decreased with increased storage time during both years, indicating that PMTV-induced necrosis development is dependent on potato cultivar and post-harvest storage. The median (50% of tubers with symptoms) survival times were estimated as 167 and 214 days for red- and other market type potato cultivars. The information from this study could potentially help growers regulate storage times for their cultivars to minimize tuber quality loss due to PMTV-induced tuber necrosis.