Performance of potato minitubers in a controlled environment after different storage periods

Summary Minitubers of cultivars Agria and Liseta were harvested from the same plantlets on three dates. After each harvest, tubers were dried (1 day), cured (13 days) and cold stored at 2 °C in darkness and 80 % RH. Their performance was studied 65, 128, 191, 254, 317, 380, 443, 506 and 569 days after harvest. Minitubers (1–2 g) were planted in pots and grown for 8 weeks in a controlled environment. After 191 days of storage their growth was still extremely poor. In both cultivars, tallest plants and largest leaf areas per plant were observed in plants from tubers from the second and third harvests that had been stored for 317 days. Highest stem numbers, yields (total dry matter, tuber fresh weight) and harvest indices were achieved with 443 days storage with cv. Agria and 569 days storage with cv. Liseta. Tubers from the first harvest behaved slightly differently.     

The Impact of Retail Light Source on Greening of Russet Burbank Potato Tubers

The use of accent lighting in retail stores has focused illumination on potatoes for greater consumer awareness. Unfortunately, this directed light on displayed potatoes may impact the rate or level of tuber greening. The objective of this study was to evaluate the influence of various retail accent light sources on greening and quality of illuminated tubers. Two separate experiments exposed ‘Russet Burbank’ potato tubers to fiber optic, ceramic metal halide, fluorescent, fluorescent with filter lighting (experiment 1) and fiber optic, halogen, and fluorescent lighting (experiment 2). In each experiment, tubers were exposed to a consistent light intensity (1390 lx in experiment 1 and 1300 lx in experiment 2) in addition to a dark control. Tubers were illuminated for 22 h per day at an ambient room temperature of 22 C. Six randomly selected tubers were evaluated for level of greening, chlorophyll concentration, and weight loss at day 0, 2, 4, 7, and 9. Total glycoalkaloid content was analyzed at days 0 and 9. In experiment 1, the fiber optic and fluorescent illuminated tubers showed significantly lower chlorophyll content compared to the ceramic metal halide light source. There was no significant difference in chlorophyll level or greening rating between the fluorescent light source and fluorescent with filter. In experiment 2, the fiber optic illuminated tubers had lower chlorophyll content and less visual greening compared to the halogen illuminated tubers. Total glycoalkaloids were not significantly impacted by light source. The use of fiber optic lighting or a combination of fiber optic lighting with standard fluorescent lighting would retard the progression of greening in the retail store yet potentially highlight the commodity for consumer eye-appeal.     

Ascorbic acid and glycoalkaloid content of Atlantic and Superior potato tubers as affected by supplemental irrigation and soil amendments

Atlantic and Superior potato (Solanum tuberosum L.) tubers were collected at harvest from two field experiments in Maine during 1993 and 1994. Tubers were analyzed for ascorbic acid (ASC) and total glycoalkaloid (TGA) concentration within one month of harvest and after 4 to 5 months of storage at 10 C. ASC concentration was significantly higher in Superior than Atlantic at harvest and after storage. TGA concentration was consistently higher in Atlantic than Superior. Irrigation tended to slightly reduce ASC and increase α-solanine concentrations when applied too late in the season for yield benefits. Storage decreased tuber ASC content, but no specific pattern was observed for TGA changes. Soil amendment programs using compost and manure (22 Mg ha^?1 potato compost + 45 Mg ha^?1 manure) did not dramatically affect tuber ASC or TGA concentrations. ASC content of the tubers declined dramatically in storage, but no consistent pattern was found for tuber TGA changes. We conclude that genotype, growing environment, and storage time play much stronger roles in determining tuber ASC and TGA levels than do irrigation and soil management programs. We observed a negative relationship between the average tuber size of the assayed samples and ASC concentration in fall samplings; however, this relationship was not observed from storage. Average tuber size and TGA content generally displayed a negative relationship.     

Effect of Different Defoliation Systems of Ryegrass–Clover on Yield and Selected Quality Parameters of Organic Potatoes (Solanum tuberosum L.) for Industrial Processing at Harvest and After Storage

The nitrogen supply plays an important role in achieving quality characteristics in organic potato farming. Different defoliation systems of ryegrass–clover may influence the amount of fixed nitrogen available to the tubers. In a field experiment, the effect of different defoliation systems (cutting, mulching and a combination of them) of the pre-crop ryegrass–clover on selected quality attributes of organically grown potatoes, destined for processing into French fries (cv. Agria) or crisps (cv. Marlen), were conducted in two consecutive years (2003 and 2004). Parameters studied included compounds related to the sensory properties of potato food (tuber dry matter, starch, reducing sugars) as well as nutritional quality (nitrogen, minerals). Selected agronomic parameters such as total tuber yields and tuber size distribution were also compared. Furthermore, the influence of additional slurry fertilisation and 4 months of storage on these parameters were investigated. Total yields and portion of tuber yield 50–60 mm were significantly affected by the pure mulching variant in 2003. In 2003, the starch concentration at harvest, as well as after storage, was above the required minimum of 22% (cv. Marlen) and 19% (cv. Agria), while in 2004, this was slightly beneath these values. In 2004, a significant increase of starch concentration by the pure cutting variant was observed. In both years, mulched ryegrass–clover caused a decrease in tuber DM contents of 2.10 and 3.54%, respectively, compared to the cutting systems. Fertilisation significantly decreased DM and starch concentration. In 2004, the reducing sugar concentration of tubers of cv. Marlen from the pure cutting system was with 2.1 g kg^?1 FM above the required maximum of 1.5 g kg^?1 for crisps. In addition, storage led to a three to fivefold increase of reducing sugars concentrations in the tubers in this year. After slurry fertilisation, 8.8% higher N contents and up to 36% higher K concentrations were measured. Mulching of the pre-crop combined with slurry application led to an up to 61% higher tuber K concentration compared to the cutting system. The results indicate that different defoliation systems of the pre-crop ryegrass–clover and slurry fertilisation had only minor effects on internal tuber quality attributes. Quality parameters were more affected by the prevailing weather conditions in combination with the genotype of different potato cultivars.     

Photoinduction of glycoalkaloids in cured potatoes

Curing of Sebago potatoes for 10 days at 25°C prior to common storage at 5°C, reduced the responsiveness of tubers to photoinduced glycoalkaloid synthesis. Continuous illumination with 15 and 25-Watt incandescent light for 10 days increased glycoalkaloid content of peelings (12–14% of tuber weight) in uncured potatoes by a factor of 3.2 and 2.8, respectively, while the corresponding factor for cured tubers was only 1.8 for both lights. The peeled tuber portion (86–88% of tuber weight) had negligible amounts of glycoalkaloids, averaging about 1 mg per 100 g of fresh weight. The rise of glycoalkaloid levels in peels of uncured tubers was nearly linear to 164.7 mg/100g (15W light) with no indication of levelling off. In peels of cured tubers, the rise began only after the 4th day of light exposure with an apparent maximum and levelling off at 94.7 mg or approximately 43% lower than the final TGA levels in uncured tubers.     

Post-harvest characteristics of potato minitubers with different fresh weights and from different harvests. II. Losses during storage

Summary Storage losses were studied in minitubers of cvs Agria and Liseta, using five fresh weight classes (<0.50 g, 0.5–0.99 g, 1.00–1.99 g, 2.00–2.99 g, ≥3.00 g), and three successive harvests of the same plantlets. After each harvest, tubers were dired at room temperature (1 day), curred at 18 °C (13 days) and stored at 2 °C (540 days). Two kinds of storage losses were considered: (a) losses of entire tubers because of deterioration, and (b) fresh weight losses of the other tubers. Both kinds of losses were higher in cv. Liseta, in tubers with lower fresh weights and in tubers from the first harvest. Almost all minitubers ≥0.5 g from later harvests and from both cultivars survived storage for 1.5 years. Deterioration occurred mainly from 6 to 12 months of storage. Tubers which deteriorated during cold storage had already shown high weight losses during curing.     

Potato glycoalkaloids: Increases and variations of ratios in aged slices over prolonged storage

Four commercial cultivars of potatoes were maintained under normal storage conditions at 44 F for 34 weeks. Except for a final 10 week interval tubers were withdrawn at 6 week intervals. After slicing, a portion of the slices was immediately analyzed for total glycoalkaloid content. The remaining slices were aged for four days in the dark at room temperature, then similarly analyzed. The total glycoalkaloid content of the aged slices increased dramatically on aging. This increase on aging of slices reached a maximum early in storage then decreased gradually over the storage period. In determining the individual glycoalkaloids, α-solanine and α-chaconine both increased in these slices, but the greatest increase was in the former. Appearing solely in the aged slices of the Kennebec variety, α-and β-solamarine appeared early in the storage period and gradually decreased over the storage period. Analyses of the unaged slices indicated that the glycoalkaloid content and composition of the potato tubers was little affected by storage. Aging of potato sprouts did not change their glycoalkaloid content.     

储藏条件对马铃薯块茎肉质部分α-茄碱含量的影响

研究不同储藏条件下马铃薯块茎肉质部分α-茄碱的含量变化.在不同温度、光照、时间条件下储藏马铃薯,用乙醇-乙酸法提取马铃薯块茎肉质部分α-茄碱,用高效液相测定其含量.结果表明,在储藏温度为8、15、25℃条件下,样品中α-茄碱含量分别为0.9556％、3.923％、7.520％;在储藏时间为6、12、18 d条件下,样品中α-茄碱含量分别为3.923％、6.187％、9.257％;在有光照、无光照条件下样品中α-茄碱含量分别为7.520％、4.665％.马铃薯块茎肉质部分α-茄碱含量与储藏温度、时间呈正相关,光照对α-茄碱含量的影响显著.马铃薯应该在避光、低温条件下储藏并要控制储藏时间.     

Glycoalkaloid content inSolanum species and hybrids from a breeding program for resistance to late blight (Phytophthora infestans)

As part of an effort to study the relationship between the “glycoalkaloid trait” and genetic resistance to late blight (Phytophthora infestans), glycoalkaloid content in tuber and foliar tissues from a wide genetic background withinSolanum, includingS. demissum, S. iopetalum and 15 hybrids selected from a backcrossing breeding scheme was determined. Analysis of variance indicated significant genotypic effect on total glycoalkaloid, solanidine, α-solanine, and α-chaconine content in both tubers and leaves. Tubers from wild potato species commonly contain glycoalkaloids in concentrations that exceed international health regulations for human consumption (20 mg/100 g fresh weight). In this study,S. demissum andS. iopetalum were highest in total tuber glycoalkaloids among all materials tested, with 70.4 and 76.2 mg/100 g fresh weight, respectively. In contrast, both commercial cultivars had the lowest concentration, both below the safety limit. Solanine was more abundant than chaconine in all but one genotype. All hybrids were intermediate to low in total glycoalkaloids. Except for the two wild species, glycoalkaloid concentration in leaves of all genotypes studied was at least twice that in tubers, with glycosylated forms accounting for more than 80% total glycoalkaloid content. Correlation between tuber and foliage alkaloids was poor. In view of the observed field resistance to late blight, it was concluded that tuber glycoalkaloid content may not be responsible for such resistance.     

Effects of a short period of drought on changes in tuber volume and specific leaf weight. II. Diurnal changes

Summary Single-stemmed potato plants, cv. Bintje, were grown on a nutrient solution under controlled conditions. They were exposed to a short drought stress, or remained untreated. Short-term changes in tuber volume and in specific leaf weight were measured non-destructively. Tubers from control plants increased rapidly in volume during the night and did not grow, or even shrivelled during the day. Tubers of stressed plants did not show a uniform response; some tubers markedly declined in volume during the day. The patterns of volume increase of stressed plants became erratic after the stress, mainly because some plants never fully recovered. Patterns of diurnal fluctuation in tuber volume were similar to diurnal changes in specific leaf weight; tubers within the same stressed plant sometimes reacted differently. In these cases the effects on the diurnal fluctuation partly reflected the long-term effects, reported in an earlier paper.     

Effects of Foliar and Tuber Sprout Suppressants on Storage of Ware Potatoes under Tropical Conditions

Potato (Solanum tuberosum L.) is an important source of dietary carbohydrate and cash income generation for farmers in the tropical highlands of Kenya. The feasibility for cold storage at the farm level is limited due to the high costs of maintaining such a facility and there is limited data on the long-term post-harvest storage and quality of tubers of tropical-adapted cultivars. Application of sprout suppressants to control premature sprouting of ware potato is an attractive proposition. The objectives of this study were to evaluate the efficacy of pre-harvest foliar applications of paclobutrazol (PBZ) and ethephon for sprout suppression on ware potato tubers in storage. Post-harvest spray applications of Isopropyl N-(3-chlorophenyl carbamate) chloropropham (CIPC) and 1,4-dimethylnaphthalene (DMN) on tubers as fog was also evaluated. Potato cultivars had varying levels of tuber dormancy. The tubers were stored at ambient temperature (23 C) and evaluated weekly for 24 weeks for percent of tubers sprouting, length of longest sprouts, tuber weight loss and assessed for dormancy for 24 weeks. Paclobutrazol prolonged tuber dormancy by 21–31 days and reduced tuber weight loss. Ethephon treatment had no effect on dormancy and tuber weight loss. Potato tubers treated with CIPC had greater sprout control than the other treatments in storage. Tuber response to DMN treatment varied among the three potato cultivars evaluated. The findings from this study imply that PBZ is effective in prolonging potato tuber dormancy for short-term basis at 23 C, while CIPC applied on tubers was effective for long term storage. Optimization of post-harvest potato storage can improve food security in the highland tropics.     

Failure of systemic insecticide-nematicides to affect total glycoalkaloid content of harvested potato tubers in northern Florida

Tubers of Sebago, Pungo, and Wauseon cultivar potatoes were analyzed for total glycoalkaloid (TGA) content following treatment with systemic insecticide-nematicides in two experiments. The treatments were at plant applications of aldicarb, carbofuran, and phenamiphos, each applied at 3.4 kg ai/ha in-the-row; oxamyl, and ethoprop at 4.5 kg ai/ha in-the-row; and fensulfothion applied at 2.2 kg ai/ha in-the-row; and three 1.1 kg ai/ha overall foliar applications of oxamyl both alone and in combination with an at plant application of carbofuran at 4.5 kg ai/ha in-therow. None of the nematicide treatments significantly affected TGA content of potato tubers at harvest. Similarly, there were no significant differences in tuber TGA levels between the cultivars Pungo and Sebago in one experiment. In the other experiment Pungo and Wauseon tubers had significantly lower levels of TGA than Sebago. There were no cultivar X nematicide treatment interactions observed in either experiment.     

Relationship of potato tuber periderm resistance to plant water status

Potato (Solanum tuberosum L. cv. Russet Burbank) tuber periderm resistance to water loss was monitored during the harvest season. Periderm resistance of tubers from water-stressed plants was compared with tubers from unstressed plants throughout a six-week harvest period, in order to determine the effect of plant condition on tuber resistance to water loss. Tubers stored for ten days at 4°C immediately following harvest were also monitored to determine if storage enhanced periderm resistance and if any difference occurred between tubers from stressed vines compared with those from unstressed vines. During the harvest season, tuber resistance to water loss was positively correlated with plant water stress, as measured by leaf water potential and leaf diffusive resistance. Storage of tubers after harvest also caused an increase in periderm resistance. The commercial practice of vine killing, therefore, may have a positive effect on reducing weight loss in storage by enhancing the resistance of tuber periderm to water loss.     

Determination of Glycoalkaloids in Potatoes and Potato Products by Microwave Assisted Extraction

Potato glycoalkaloids can reach levels that are harmful to human health. A rapid and reliable microwave assisted extraction method for quantitative analysis of α-solanine and α-chaconine content in raw potato and potato based products is presented. A chemical microwave was used to determine optimal temperature and pressure conditions for the extraction of α-solanine and α-chaconine from Idaho grown tubers and six commercially available mashed potato products. Recovery efficiency of glycoalkaloids was 37% greater by microwave assisted extraction (19.92 mg/kg glycoalkaloid) as compared to conventional solid/liquid methods (12.51 mg/kg glycoalkaloid). Optimal extraction of glycoalkaloids from potato samples dissolved in methanol was achieved using a microwave reactor set to 90 °C for ten minutes. The interior of Idaho grown tubers was determined to contain lower levels of glycoalkaloids (19.92 mg/kg dry weight; 6.5 ± 1.78 mg α-solanine and 13.40 ± 1.65 mg α-chaconine), as compared to commercial potato products (33.86–81.59 mg/kg).     

Effect of Harvest Date on PI2, Total Protein, TGA Content and Tuber Performance in Potato

Proteinase inhibitor 2 (PI2), isolated from potatoes is associated with the release of cholecystokinin (CCK), a satiety factor in humans. PI2 is the active ingredient of Slendesta® Potato Extract. The effect of harvest date on the levels of proteinase inhibitor 2 (PI2), total protein content and total glycoalkaloids (TGA) was studied in two potato (Solanum tuberosum L.) clonal lines. In addition, tuber specific gravity, tuber yield, and tuber size distribution were measured in response to harvest date. The two potato clonal lines designated as KI-PSt0018 and KI-PSt0034 were planted in a randomized complete block design with four replicates. Tubers were harvested at four different dates during the growing season; 4 weeks and 2 weeks to vine-kill; at vine-kill; and 2 weeks post vine-kill. Sample tubers from these four harvest dates and from 2 months of storage, post vine-kill stage were analyzed for PI2, total protein and TGA. Harvesting at different dates had a significant influence on most of the traits studied in both clonal lines. The two clonal lines responded differently to different harvest dates for all traits except PI2 and specific gravity. PI2 levels increased with maturity with the highest levels observed at full maturity in both clonal lines. The protein levels did not show any specific trend in either clonal line. TGA levels increased gradually in small increments with maturity in KI-PSt0018 but did not have a clear pattern in KI-PSt0034. Tuber yield and size increased with maturity of the crop in both clonal lines. Higher tuber yields were seen during final vine-kill and 2 weeks post vine-kill compared to the earlier stages of harvest in both clonal lines. Tuber specific gravity declined when tubers were left in the ground for 14 to 21 days after vine-kill in both clonal lines. This study indicated harvest of potato prior to vine-kill is not beneficial for the extraction of PI2 for use as functional food or dietary supplement ingredient.     

Seed Potato Performance after Storage in Light at Elevated Temperatures

In regions with short growth seasons, it is of great importance to use potato (Solanum tuberosum L.) seed tubers with a high growth vigour and a short growth cycle. Such qualities may be obtained by treatments advancing the physiological age of the seed tubers. In this study, we have exposed tubers from four cultivars to various combinations of temperature and light conditions (green-sprouting) for 3–7 months in controlled climate. Subsequent sprout quality, seed tuber health and performance were studied in laboratory, greenhouse and field trials. Satisfactory short, sturdy and leafy sprouts were produced even after 7 months storage at 15 °C under light exposure. An assay of black scurf (Rhizoctonia solani) on the tuber skin showed that light exposure significantly reduced the occurrence compared with dark-stored tubers, while the average effect of storage temperatures was insignificant. In general, green-sprouting advanced emergence and plant growth by 1–2 weeks, and showed early tuber initiation and growth, compared to untreated material. Yields, 107 days after planting in the field trial, did not deviate significantly from untreated tubers. However, plant development at harvest was in accordance with general responses to physiological ageing of potato seed tubers, i.e. still tall and immature plants from untreated tubers, and short and mature plants from aged tubers. Results demonstrated the possibility of successful long-term storage of potato seed tubers in light at elevated temperatures and a potential for earlier harvests and higher early yields from such treatments.     

Enzyme-linked immunosorbent assay (ELISA) for the detection of potato leafroll virus and potato virus Y in potato tubers after artificial break of dormancy

Summary Conditions necessary for the detection of potato leafroll virus (PLRV) and potato virus Y (PVY) in tubers from primary and secondary infected plants were investigated. Tubers were analysed before and after breaking dormancy by rindite treatment. PLRV was reliably detected indormant tubers whereas PVY was readily detected only when tubers had been rindite-treated and held for two to three weeks at 22°C and high humidity in the dark. PLRV occurred in higher concentration at the heel end than at the rose end of infected tubers and the concentration remained nearly unchanged during the experimental period of 35 days, whereas PVY was found to be more concentrated at the rose end and was rapidly accumulating in the tubers after the break of dormancy. In dormant tubers PVY concentration dropped during storage at 22°C. The use of ELISA for tuber indexing is discussed.     

A comparison of variability in storage behaviour of seed tubers from true potato seed and clonal tubers

Summary The tuber-to-tuber variability in storage behaviour of seed tubers from true potato seed was compared with that in clonal seed tubers after storage in the dark, in diffused light, or in diffused light with a single desprouting. The variability was estimated by calculating standard deviations of length, number and weight of sprouts, and tuber weight loss. After dark storage, the variability of these variables was greater in seed tubers from true potato seed than in clonal seed tubers. After storage in diffused light with a single desprouting, the variability of number, length and weight of sprouts of seed tubers from true seed was not statistically different from that observed in clonal seed tubers. All storage treatments resulted in a greater variability of tuber weight loss in seed tubers from true potato seed than in clonal tubers.     

The effect of controlled atmosphere storage at 4°C on crisp colour and on sprout growth,rotting and weight loss of potato tubers

Summary After three weeks curing at 10°C, potato tubers cv. Record were stored at 4°C under different controlled atmospheres (CA) for six months to study the effect on crisp fry colour, sprout growth and rotting. Combinations of low levels of CO₂ (0.7–1.8%) and low levels of O₂ (2.1–3.9%) gave a significantly lighter crisp colour, low sprout growth and fewer rotted tubers compared with 0.9% CO₂ and 21.0% O₂. Tubers stored in these conditions. showed a significantly higher weight loss and shrinkage after reconditioning. High CO₂: low O₂ combinations during storage completely inhibited sprout growth and caused the darkest crisp colour, but after reconditioning tubers gave the same level of sprouting and crisps as light as the other CA combinations. Furthermore these combinations, especially CO₂ at 10 or 15%, increased the onset of rotting. Also our results showed that at low concentrations of CO₂ (0.7–1.6%), and low O₂ (2–2.4%) there was an increase in tuber rotting.     

Differential Growth Response and Minituber Production of Three Potato Cultivars Under Aeroponics and Greenhouse Bed Culture

We have evaluated and compared different methods and cultivars for the production of quality prebasic seed in potato. Two cultivation systems, aeroponics and greenhouse beds with a peat moss substrate, and three potato cultivars with different vegetative cycle, Agria, Monalisa and Zorba, were assayed. Plants in the aeroponic system showed increased growth and their vegetative cycle extended between 12 and 36 % compared to the plants cultivated in greenhouse beds. Flowering and tuberization dates, Absolute Growth Rates (AGR) during the period of 60 days after planting (DAP) and height presented a wide variation between cultivars. Zorba showed earlier flowering and tuberization, lower AGR and reached a minor height at 60 DAP. Instead the late season cultivar Agria showed later flowering and tuberization, presented higher AGR and reached an increased height at 60 DAP. The total tuber yield per plant was between 34 and 87 % higher in the aeroponic system, with a marked difference for the earlier cultivars Zorba and Monalisa. Tuber numbers increased between 60 and 80 %. Minituber production in aeroponics showed a better size distribution, with a reduction in the percentage of tubers smaller than 12 mm of between 33 and 86 %. In this soil-less culture system average tuber weight increased in Zorba and Monalisa over 60 % but was lower for Agria. Further studies are needed to optimize aeroponics system, which can be considered a high yield potato multiplication system, particularly for early or mid season potato cultivars that may produce best quality minitubers.