Effects of ethylene and 1-methylcyclopropene on potato tuber sprout control and fry color

The study examined the efficacy of 1-methylcyclopropene (1-MCP), an anti-ethylene compound, as a preventative treatment for ethylene-induced fry color darkening in potato (Solanum tuberosum L.) tubers, without reducing the effectiveness of ethylene as a tuber sprouting control agent. The experiment was conducted for two years with ‘Shepody’ and ‘Russet Burbank.’ Tubers of each cultivar from four separate growers received one of the following treatments: Air (control), Air + 1-MCP (1 (μL.L^-1 for 48 h), isopropyl N (3-chlorophenyl) carbamate (chloropropham; CIPC; 1% a.i. [v/v]); continuous ethylene (4 μL.L^-1) in air; continuous ethylene pre-treated with 1-MCP once; continuous ethylene pre-treated with 1-MCP and repeated monthly; and continuous ethylene pre-treated with 1-MCP and repeated bi-monthly. Treatment started after suberization and cooling to 9 C, and samples were evaluated at 3-wk (year 1) or 4-wk (years 2 and 3) intervals thereafter until April (Shepody) or June (Russet Burbank). Sprout growth (sprout fresh weight per tuber), fry color (Agtron reflectance units), tuber weight loss, incidence of disease infection and internal disorders were evaluated. Weight loss, tuber infection, and the occurrence of disorders were not affected by any of the treatments. Sprout growth was controlled by the continuous ethylene supply in both cultivars, and single or multiple additions of 1-MCP to the ethylene treatment did not affect the ethylene control of sprouting. As expected, ethylene treatment alone enhanced fry color darkening in both cultivars. In Russet Burbank tubers, fry color was not darkened in any of the ethylene + 1-MCP (once, monthly, or bimonthly) treatments. In Shepody, fry color was not darkened in the ethylene + 1-MCP monthly or bimonthly treatments, but started darkening 4 wk after exposure in the single ethylene + 1-MCP treatment. It is concluded that 1-MCP can be used to control fry color darkening induced by ethylene without blocking ethylene control of tuber sprouting. However, the number of 1-MCP applications required may vary with the cultivar, e.g., one application was sufficient in Russet Burbank but not in Shepody.     

Growth-room and field studies with seed tubers treated with ethylene and 1-methylcyclopropene (1-MCP) during storage

Based on ethylene management in potato storage, we hypothesized that the applied treatments would modify number of sprouts per seed tuber. Thus, in combination with in-row spacing (closer for seed, wider for processing) in the field treatments will give either (1) a high number of small tubers destined for seed use, or (2) a relatively smaller number of large, uniform tubers suitable for processing. A three-year study (2001–2003), conducted with two french fry processing cultivars, Russet Burbank (RB) and Shepody (SH), aimed at the development of a novel modified atmosphere seed tuber storage treatment. Seed tubers were stored at 4 C from October to May of each year in a cold room under five modified atmospheric regimes: (1) air ventilation only (Control); (2) 4 µl L^?1 ethylene applied continuously beginning in November and (3) beginning in February; (4) 1 µ1 L^?1 MCP (1-methylcyclopropene) applied as a gas for 48 h only in early December followed by continuous 4 µl L^?1 ethylene and (5) MCP alone applied as above. Each year, once a month (mid-January until end of April), a number of seed tubers was taken from each storage treatment, planted to pots and grown for 4 wk in a growth-room. In these studies, shoot emergence from the ethylene-treated seeds of both cultivars occurred significantly earlier, giving higher number of stems per tuber and stolons per stem than Control and MCP treatments. Moreover, the time to emergence after planting decreased with the increased length of storage. Field studies that were conducted from the end of May (planting) until October each year, produced similar trends (although not significant atP≤0.05) and resulted in a higher number of tubers per stem. In RB at the closer in row spacing (30 cm) used for seed production, ethylene enhanced yield of smaller tubers in the 30- to 115-g and 115- to 300-g categories. The ethylene storage treatments also increased tuber number per plant, but not the total mass of harvested potatoes. The MCP treatment, in combination with the wider in-row spacing (40 cm) used for the production of processing tubers, significantly increased the percentage of large tubers (>300 g). In SH, contrary to RB, the ethylene treatments did not alter tuber size distribution and the application of MCP reduced tuber size rather than increasing it. Results from this study suggest that both ethylene and MCP can be used in seed potato storage to influence the tuber size distribution of the crop from that seed.     

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.     

Using Ethylene Gas and Chlorpropham Potato Sprout Inhibitors Together

Marketplace preference for lower pesticide residues in foods has led to research to reduce the residue of chlorpropham (isopropyl N-3-chlorophenyl carbamate; CIPC), a postharvest-applied sprout inhibitor which is widely used around the globe to prevent sprouting of stored potatoes (Solanum tuberosum L.). Ethylene gas, an effective, safe and non-toxic sprout inhibitor used in several countries, sometimes has negative effects on the colour of processed potato products when used alone. Trials were conducted over 3 years using cv. Shepody (French fry) and cv. NorValley (potato chips/crisps) to determine whether a combination of these two sprout inhibitors, at reduced dosages, could inhibit sprouting while maintaining good processing colour. CIPC applied at 0, 0.1, 0.25 and 1.0 times the recommended dosage was combined with 4 μll⁻¹ of ethylene gas applied or no ethylene at all (0 ethylene), for 1 day in 4 days, for 1 day in 2 days or continuously, in a factorial design. Sprout inhibition in both cultivars was excellent at all levels of CIPC application except the 0 rate. In both cultivars, sprouting was inhibited by the continuous ethylene treatment. However, all levels of ethylene exposure except the 0 rate negatively affected processing colour in both cultivars. The darkening was dose dependent, whereby the colour was darkest in continuous ethylene and was less affected by the intermittent exposures. In continuous ethylene, the colour was progressively lighter during storage after initial darkening. Shepody tubers appeared to be more sensitive to ethylene than the NorValley tubers. In Shepody only, colour in the ethylene of 1 day in 4 days treatments was progressively darker with increasing time in storage.     

Auxin-induced sprout growth inhibition: Role of endogenous ethylene

The role of endogenous ethylene in auxin-mediated tuber sprout growth inhibition was determined in potato (Solanum tuberosum L. cv. Russet Burbank) minitubers. Treatment of tubers with biologically active auxins resulted in a transient, dose-dependent increase in ethylene production and inhibition of sprout growth. Biologically inactive auxin analogs elicited neither response. Continuous exposure to > 0.001 μL L^-1 exogenous ethylene inhibited sprout growth in a dose-dependent manner with complete inhibition occurring at ethylene concentrations ≥1 μL L^-1. In further studies with the active auxin α-naphthalene acetic acid (NAA), the role of ethylene in auxin-induced sprout growth inhibition was determined using ethylene biosynthesis and action inhibitors. The ethylene biosynthesis inhibitor aminoethoxyvinylglycine reduced NAA-induced ethylene biosynthesis by over 80% but had no effect on sprout growth inhibition. The non-competitive ethylene action inhibitor silver thiosulfate had no effect on NAA-induced sprout growth inhibition. Similarly, both the competitive ethylene action inhibitor 2,5-norbornadiene and the irreversible action inhibitor 1-methylcyclopropene were ineffective in reducing NAA-mediated sprout growth inhibition. Collectively, these results do not support the proposal that, in the case of potato tuber sprouts, auxininduced growth inhibition is mediated by endogenous ethylene action.     

Methods to Minimize the Effect of Ethylene Sprout Inhibitor on Potato Fry Colour

Ethylene is an effective potato (Solanum tuberosum L.) sprout inhibitor, but it often darkens fry colour. Trials were conducted over nine consecutive storage seasons to identify ethylene application methods which would mitigate darkening while retaining adequate sprout inhibition, using cv. Russet Burbank plus cvs Shepody, Asterix and Santana in some years. Tubers were stored for up to 35 weeks in closed chambers with ethylene gas delivered via the ventilation airstream. Exposure to continuous 4 μl l⁻¹ ethylene after suberization and cooling were completed was designated the ethylene check. Alternative ethylene treatments included commencing exposure either before or after suberization was completed; gradually introducing the ethylene either by a concentration gradient of eight steps over 4 or 8 weeks or by increasing the duration of exposure from 6 to 24 h per day in four weekly steps; repeatedly interrupting exposure for several hours per day or for durations of 1 or more days; and warm storage. Selected ethylene treatment combinations were applied in each year, plus untreated controls, chlorpropham-treated (CIPC) checks and ethylene checks. Sprout growth, fry colour, loss of mass and disease incidence were evaluated at regular intervals. In all cultivars and all years, the ethylene check darkened fry colour more than the other treatments. Commencing before suberization ended, gradually introducing the ethylene by either concentration or time gradient and interrupting the exposure all reduced the negative effect of ethylene sprout inhibitor on fry colour. Continuous ethylene treatments inhibited sprout growth as effectively as CIPC, except at 13 °C storage. Interruptions of 18 h and 2 or more days reduced sprout inhibition. Regardless of cultivar variations, an early start using either a concentration or time-increment gradient had the least effect on fry colour while maintaining good sprout inhibition.     

Effect of Cooking and Processing on CIPC Residue Concentrations in Potatoes and Processed Potato Products

Residue concentrations of the sprout suppressant chlorpropham (or CIPC) were determined in raw and cooked potatoes and processed potato products, 48 h after CIPC aerosol treatment and after 30 days of subsequent storage at 4 or 12 °C. In the raw (uncooked) tuber, 48 h after CIPC treatment, the CIPC residue in the peel was 4.7 mg kg^-1, while in the peeled tuber it was 0.1 mg kg^-1. Boiling resulted in a decrease in residue concentration in the peel, but no significant differences in the residue concentration of the peeled tuber were observed. Pressure cooking resulted in a significantly increased residue concentration in the peel, but no significant change in the peeled tuber, whereas microwave cooking also did not increase the residue concentration in the peel significantly compared with that in raw tubers. Also the trend towards increases in residue concentration in microwave-cooked peeled tubers was not significant. The CIPC residue concentration detected in peeled tubers was 0.4–0.7 mg kg^-1 after boiling, 0.4–1.5 mg kg^-1 after pressure cooking and 0.4–3.8 mg kg^-1 after microwave cooking. The highest values were always found for tubers stored for 30 days at 4 °C. Processed products such as crisps, French fries, dehydrated sliced potatoes and starch contained different concentrations of CIPC residue, which was also detected in the cooking water and frying oil. The highest residue concentrations detected were 0.7, 4.7, 1.3 and 0.2 mg kg^-1 in crisps, French fries, dehydrated sliced potatoes and starch, respectively. The highest CIPC residue concentration observed in raw potatoes was much lower than the maximum residue level of 10 mg kg^-1 prescribed by the European Union.     

Maleic hydrazide effects on tuber yield, sprouting characteristics, and french fry processing quality in various potato (Solanum tuberosum L.) cultivars grown under argentinian conditions

Field trials were carried out during 1995–1998 in commercial crops of five potato cultivars grown at several locations in Argentina to test maleic hydrazide (MH potassium salt, 36% ) effects on tuber yield, sprouting characteristics, and processing quality. MH was applied at growth stage IV, when developing tubers were 40–70 mm, at 9, 10,12 and 14 1 ha^-1 in single or split treatments. MH treatments did not produce phytotoxicity symptoms in the foliage and did not decrease tuber yield. MH increased tuber yield in Kennebec, Russet Burbank and Shepody in several experiments, while not in Atlantic and Ranger Russet. MH treatments delayed initial sprouting date and inhibited sprout growth during storage periods up to 8 months, which resulted in lower weight losses due to sprouting. Tuber dry matter content and fry color were similar or in some cases improved due to MH treatments, while no consistent results were found regarding reducing sugar content.     

The effects of ozone and 1,8-cineole on sprouting,fry color and sugars of stored Russet Burbank potatoes

Ozone and 1,8-cineole were investigated as alternatives to isopropyl-n-(3-chloro-phenyl)carbamate (CIPC) to control sprout development of potato (Solatium tuberosum) tubers cv Russet Burbank during long-term storage. Sprout development was similar in ozone-treated and air-stored tubers, but both had much larger and more numerous sprouts than CIPC-treated tubers. Sucrose and reducing sugars in ozone-treated tubers were similar to levels in air-stored potatoes. Fry color was not different among potatoes stored in ozone, air and CIPC. Conversely, potatoes treated with 1,8-cineole did not produce any sprouts during the 25 week study. The fry color of tubers exposed to cineole was darker than either air-stored or CIPC-treated tubers. Sucrose and reducing sugar levels were higher in cineole-treated tubers than in tubers treated with CIPC.     

Potato Sprout Growth Suppression by Menthone and Neomenthol, Volatile Oil Components ofMinthostachys, Satureja, Bystropogon, andMentha Species

The replacement of synthetic pesticides such as chlorpropham (CIPC) with effective potato sprout suppressants that have negligible environmental impact is needed due to increased concern for consumer health and safety. To date, however, only S-(+)-carvone, a monoterpene produced from caraway seeds, has been developed commercially as a competitive product to CIPC. Consequently, the effects of menthone and neomenthol vapor were compared to S-(+)-carvone for sprout suppressant efficacy as well as for effects on soluble sugar levels, respiration, and processing quality during high and low temperature storage. In the majority of treatments, tubers were enclosed in 3.8 1 glass jars at 25 C. Liquid test compounds were applied to a 10-cm-long x 2-cm-wide filter paper strip (Whatman No. 1) enclosed in each jar. Treatment with either menthone or S-(+)-carvone at 5 ul liquid/1 of treatment volume gave complete sprout suppression in non-dormant Russet Burbank tubers. An examination of changes in CO₂ output, glucose, or sucrose levels over 4 wk at 10 C indicated that the effects of menthone and S-(+)-carvone were similar. In addition, menthone significantly inhibited sprouting without adversely affecting the percentage glucose content or sucrose content when this compound was applied at 4 ul/l to five-month-old, non-dormant tubers of AC Novachip, Russet Burbank, Shepody, and Snowden for two months at 10 C. Menthone and neomenthol were five to ten times more effective in sup pressing tuber sprouting than S-(+)-carvone when applied together at 0.5 ul/l each.     

Effect of sprout inhibitors on potato tubers (Solanum tuberosum L.) stored at ambient or reduced temperatures

Summary Single and combined applications of three sprout inhibitors, maleic hydrazide (MH), isopropyl 3-chlorophenylcarbamate (CIPC) and isopropyl phenylcarbamate (IPC) mixed with CIPC in a commercial formulation coded AMK (Tixit-C, Sandoz, S.A.E., Barcelona, Spain; 2.0% IPC +0.7% CIPC) were tested on potatoes stored from March to June under ambient conditions (20–30°C, 30–80% RH), and in a store with passive evaporative cooling (16–30°C, 75–95% RH). All treatments were more effective in reducing physiological losses, sprouting, and sprout growth in the cool than in the ambient store. AMK, CIPC and MH+AMK caused most sprout suppression. All treatments increased tuber rotting but there were no significant differences in numbers rotted by MH, MH+CIPC, CIPC (single treatment) and the untreated control. Nevertheless, the treatments can usefully extend storage life of potatoes under non-refrigerated conditions.     

Carbon Disulphide (CS<Subscript>2</Subscript>) Promotes Sprouting and Affects the Metabolism of Harvested Minitubers Grown from True Potato Seed

Chemical agents may be used to overcome dormancy in potato tubers so as to permit early planting. In this paper, the effect of carbon disulphide on sprouting and related metabolic processes in potato tubers grown from true potato seed (TPS) was investigated. Carbon disulphide was applied to potato tubers derived from TPS, at a rate of 20 ml m^?3 container volume for 72 h. It accelerated tuber sprouting and increased tuber weight loss. It also caused an increase in the respiration rate, as well as ethylene emission from the tubers during the first 6 days after treatment. The respiration rate of carbon disulphide-treated tubers remained at a higher level than that of untreated controls for 35 days after treatment. In addition, carbon disulphide increased the concentrations of the soluble sugars sucrose and fructose, but not glucose, in the tuber tissues (buds, parenchyma). These findings suggest that carbon disulphide releases potato minitubers from dormancy and that dormancy breakage is associated with changes in tuber metabolism prior to the visible sprouting.     

Auswirkungen des wiederholten mechanischen Entkeimens auf den Substanzverlust und die Qualität von Kartoffelknollen

The influence of a continued mechanical desprouting of potato tubers on weight loss and tuber quality was investigated in comparison with tuber irradiation (Cs 137), IPC/CIPC powder application, and the untreated control. Mechanical desprouting of tubers resulted in minimum weight loss, but it caused increased sugar content, rotting and internal sprouting. To give consumers an alternative for the conventional sprout prevention methods, tubers of varieties with a natural deep dormancy, and potato storage in low temperature should be preferred.     

Changes in chlorpropham residues in stored potatoes

Chlorpropham (CIPC)³ concentrations were measured in peel samples of tubers taken from large commercial potato storages and from test bins after aerosol application. Tuber samples were taken at different levels within the pile and at numerous sites near the surface. The minimum concentration of CIPC in the peel layer for complete inhibition of sprouting was estimated to be 20 ppm. Immediately after commercial application of CIPC, 99% of the sample sites had concentrations high enough to completely inhibit sprouting, and residues in the peel were generally highest in samples obtained from the surface and from the bottom of the pile. CIPC concentrations decreased during the storage season in nearly all sites tested. Storages differed in the rate at which CIPC was lost. Mean peel residues fell below the level necessary for sprout inhibition in some storages but not in others. The rate of CIPC loss increased at the same time that air movement to maintain the desired temperature increased. With the 20 ppm threshold level as a guide, it is possible to monitor commercial storages for sprout-inhibition status. Retreatment before peel residues drop below 20 ppm can extend sprout inhibition in storage.     

Effect of controlled atmosphere,temperature and cultivar on sprouting and processing quality of stored potatoes

Summary Three crisping potato cultivars, Record, Saturna and Hermes, were stored at 5 or 10°C in gas mixtures of either 0.5% CO₂ and 21.0% O₂ (control) or 9.4, 6.4, 3.6 or 0.4% CO₂ all combined with 3.6% O₂. There was almost complete sprout inhibition, low weight loss and maintenance of a healthy skin for all cultivars stored in 9.4% CO₂ with 3.6% O₂ at 5°C for 25 weeks. When tubers from this treatment were stored for a further 20 weeks in air at 5°C the skin remained healthy and they did not sprout. The fry colour of crisps made from these potatoes was darker than the industry standard but when they were reconditioned, tubers of cv. Saturna produced crisps of an acceptable fry colour while crisps from the other two cultivars remained too dark. Reducing sugar levels were related to fry colour both after storage and after reconditioning. The other gas combinations and the controls did not have the same effect on sprouting and none of the controlled atmosphere treatments controlled sprouting at 10°C.     

Effect of CIPC on Sprout Inhibition and Processing Quality of Potatoes Stored Under Traditional Storage Systems in India

Indigenous non-refrigerated methods like heaps and pits are used in India for short-term storage of potatoes (Solanum tuberosum L.) to avoid distress sale. Storing untreated potatoes generally results in high losses from sprouting, moisture loss and rotting. To reduce storage losses by inhibition of sprouting and to determine the suitability of stored potatoes for processing into crisps, a single spray application of a commercial formulation of 3-chlorophenyl carbamate (CIPC or chlorpropham) 50% a.i., (Oorja, United Phosphorus Limited, Mumbai, India) of CIPC (or chlorpropham) was tested on potatoes during storage from March to June under two traditional storage methods [heap (17–33 °C, 58–92% relative humidity (RH)) and pit (17–27 °C, 72–95% RH)] in 2 years [2005 up to 90 days of storage (DOS) and 2006 up to 105 DOS], using four cultivars and two rates of CIPC application (20 and 30 mg a.i. kg⁻¹ tubers). The two rates of application were comparably effective in reducing weight losses, sprouting and sprout growth in stored tubers, and the effect was more pronounced in pit storage than in heap storage. By contrast to untreated tubers, CIPC-treated potatoes remained turgid under the two storage methods and fetched market prices comparable to those for cold-stored (2–4 °C) potatoes after 105 days of storage. Reducing sugar concentrations in treated potatoes decreased during storage especially in 2006 when the initial reducing sugar concentration was higher than in 2005. Crisp colour improved only in 2005 after 90 DOS, but it deteriorated in 2006 during storage up to 105 DOS. Sucrose concentration increased tremendously during storage in 2 years. Only one cultivar (Kufri Chipsona-1) with low initial reducing sugar concentration and less sucrose accumulation during storage could produce acceptable colour crisps after storage in both years. The remaining three cultivars—with high initial reducing sugar concentration—were suitable for processing after storage in heap and pit in 2005, but not in 2006. Stored potatoes were safe for human consumption as the CIPC residue concentrations were far below the permissible level of 10 mg kg⁻¹ as prescribed by the European Union. Single spray application of CIPC (20 mg kg⁻¹ treatment) can effectively reduce storage losses in potatoes stored in traditional non-refrigerated methods of heap and pit and extend the storage life by 90 to 105 days.     

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.     

The influence of storage factors on endogenous ethylene production by potato tubers

Throughout a 7-month storage period, Russet Burbank tubers continuously ventilated at 32 F (0 C) and 45 F (7.2 C) with atmospheres of 2% O₂, air, 4% CO₂, and intermittently ventilated with air, evolved ethylene at a rate no greater than 0.008 μ 1 Kg^?1 hr^?1. Tubers stored in 80% O₂ and 12% CO₂ produced ethylene at much higher rates. In all cases where sprouting occurred, the rate of ethylene production increased. Inoculation withFusarium roseum greatly stimulated ethylene production but inoculation withAlternaria solani did not.     

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.     

Effect of soil salinity on internal browning of potato tuber tissue in two soil types

A study was carried out with potato (Solanum tuberosum; cv. Atlantic) during 2001 and 2002 to determine the effect of soil salinity on internal tuber browning. The effect of varying levels of soil salinity on proline content, polyphenol oxidase enzyme activity, and chlorogenic acid content in potato leaves and tubers was examined. NaCl treatments (2.1, 4.25, 6.38, 8.5 g NaCl L^?1) were applied to the pots, the first 46 days after planting, and four additional treatments were applied, each about 7 days apart. Increasing NaCl concentrations resulted in an increase in browning of tuber tissue and proline content in the tubers. Chlorogenic acid content in the leaves increased up to 6.4 g NaCl L^?1, but then decreased at 8.5 g NaCl L^?1 and in tubers tended to be maximal at the highest saline concentration tested (8.5 g NaCl L^?1). Increasing NaCl concentration resulted in a reduction in yield per plant and average tuber weight, and also increased tuber number. There were major differences in the impact of salinity over the 2-year period, which was probably due to the impact of the growing media; a low organic matter (about 1% OM) silty loam soil and a high organic content (about 90% OM) Muck soil were used in 2001 and 2002, respectively. Tuber browning increased linearly with salinity in 2002, but only markedly increased at 8.5 g NaCl L^?1 in 2001. Sodium and chloride ion concentration was always greater (about two times) at equivalent application rates in the 2002 trial. The high organic matter content soil retained sodium and chloride ions more effectively than the silty loam soil and enhanced the impact of increased salinity concentration on physiological properties of potato plants and particularly on tuber tissue browning and proline accumulation.