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 temperature and light during storage of young seed potatoes on initial plant development at early plantings

Summary Young seed tubers of several cultivars were exposed to storage temperatures of 4–24°C in light and dark intended to optimise their growth vigour following early plantings. In five experiments during four autumn and winter periods, the effects of storage conditions on subsequent initial plant development in the glasshouse were studied. Storage of seed potatoes for 2 months at temperatures of 12°C or higher greatly increased early plant development of five cultivars following early plantings. Light during storage had a favourable effect, but desprouting before planting was greatly disadvantageous.     

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.     

The effect of potato seed tuber age and soil temperature on the phenomenon of non-emergence

Summary In three experiments seed tubers of cvs Jaerla, Bintje and Alpha, stored at 12 °C in the dark, were planted in glasshouses on various dates at soil temperatures varying from 8 °C to 28 °C to study the phenomenon of ‘non-emergence’ with ageing seed tubers. In general the tubers were desprouted before planting. At all plantings cv. Alpha produced normal plants. The cvs Jaerla and Bintje, however, showed high proportions of the ‘little potato’ phenomenon when planted in cold soil, and high proportions of decayed tubers more frequently in warm soil. When using physiologically older seed at later planting dates, both the range of soil temperatures became wider and the proportions of seed tubers experiencing both ‘little potato’ and decay increased.     

Seed potato quality as influenced by high temperatures during the growth period. 1. Effect of storage temperature on sprout growth

Summary In the Negev area of Israel potatoes are grown in two seasons of the year: spring and autumn. Locally grown seed of cv. Up-to-Date prepared for the autumn season are grown in the spring under high-temperature conditions during the last part of the growth period. The response to storage temperature treatments consisted of different degrees of sprouting. Temperatures that encouraged bud development (12–22°C) shortened the dormant period of the tubers by about a month, and usually there is clear apical dominance. However, increasing length of the apical bud was positively correlated with storage temperature. Partial loss of apical dominance was obtained when the tubers were held at a low temperature (4°C) for at least two months after lifting. After transfer of the tubers to high temperatures for another month, there were 3 or 4 sprouts per tuber. The physiological age of seed tubers developing in the semi-arid region is discussed. Contribution from the Agricultural Research Organization, Beit Dagan, Israel 1979 Series, No 300.     

Assessment of Opportunities for Burundian Small-Scale Potato Farmers to Increase Productivity and Income

From 2014 through 2016, on-farm experiments were carried out in three provinces surrounding Bujumbura town in Burundi to improve the low potato (Solanum tuberosum) yields, which currently stand at about 6 t ha^?1. It was hypothesised that in rain-fed conditions, improved varieties, healthier seed tubers, pre-sprouting in light, proper fertilisation and protection from late blight attack would improve yield and quality, such as tuber weight, tuber size and lower brown rot incidence. The treatments in the on-farm trials at five farms in each of three sites (15 replicates) were applied in two seasons, giving 30 replicates in 580 plots. The following treatments were compared with growers’ current practices: introduction of two new varieties, use of early generation seed from a rapid multiplication scheme, earlier harvesting of a seed crop, seed storage in a diffused light store, and research-based timing and dose rate of fertilisers and fungicides. Marginal rates of return on investments were calculated at farm level and current and tested alternative technologies were compared. Costs and benefits of applying such techniques were calculated. An improved variety contributed up to 20% yield increase and healthier seed 80%. Early harvesting reduced yield by 30% and reduced incidence of brown rot in the current season, but increased it (from 21 to 39%) in the following season when tubers were replanted. Diffused light storage, alternating contact and systemic fungicide application, and application of chemical fertilisers resulted in 30, 50 and 60% yield increases, respectively. It was shown that it is possible to double yields and economic returns (marginal rates of return) under the growing conditions in Burundi when growers plant healthy pre-sprouted seed of a new variety and apply chemical fertilisers and fungicides.     

Effect of whole seed tuber size and pre-plant storage conditions on yield and tuber size distribution of Russet Burbank

Field experiments were conducted in 1995, 1996, and 1997 at Agriculture and Agri-Food Canada’s Harrington Research Farm to assess the effect of whole seed tuber size and pre-plant seed storage conditions on processing yield (> 51 mm dia.) of potato (Solanum tuberosum L. cv Russet Burbank). Following commercial storage, seed tubers were stored at 4.4 C then subjected to one of three pre-plant treatments: (1) planted directly from storage, (2) held at 10 C for 3 wk before planting, or (3) green-sprouted for 3 wk before planting. Five sizes of whole seed were used (28, 42, 56, 70, and 84 g) with a variable size cut seed treatment added for comparison. Plots were harvested 138,134, and 131 days after planting in 1995, 1996, and 1997, respectively. Cut seed produced a higher yield of tubers > 51 mm diameter in comparison to all whole tuber seed sizes, with the exception of the 28 and 56 g sizes. In terms of total yield, the 28and 42-g whole seed tubers yielded significantly less than all other seed sizes examined. Warming or greensprouting seed tubers prior to planting did not increase tuber yield. The larger whole seed tuber sizes tended to result in greater numbers of stems and tubers per plant. To maximize marketable yield of Russet Burbank planted from whole seed tubers, it is recommended that the seed be between 28 and 42 g in size. Accepted for publication 25 May 2004.     

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.     

Growth in Netted Gem potatoes as influenced by transplanting and by greensprouting

The basis of difference in field growth and yield in Netted Gem potato plants grown from greenhouse transplants, from seed which was greensprouted for two weeks prior to planting and from seed which was retained in storage until planting was studied by measuring changes in plant dry weight and leaf area throughout the season. Cut seed, approximately 70g in size, which were either two or four-cut from 142g or 283g mother tubers respectively, were used in the comparisons. Transplants were started in 7.6 cm peat pots in the greenhouse and were transplanted to the field when 10 cm high. The greensprouted seed was cut from mother tubers which had been sprouted under fluorescent light at 15–18°C for two weeks producing strong sprouts 5 mm long. Transplants, greensprouted seed and seed from mother tubers held in 3°C storage were all planted in the field May 30, 1974, coinciding with commercial plantings of Netted Gem in the province. Backup field experiments, comparing similarly treated greensprouted and storage seed and transplants, were conducted in 1974 and 1975 but were not subjected to growth analysis. All plantings were grown on a Riverbank sandy loam soil. The 1974 growing season in New Brunswick was excellent while that for 1975 was dry and required extensive irrigation. The use of transplants established a substantial advantage in terms of early emergence and yields were consistently and significantly greater than those of greensprouted-seed and unsprouted-seed plants. The transplant yield advantage was attributed to the fact that tuberization was advanced substantially compared with the latter two types. Higher relative growth rates were associated with later emergence so that the rate for plants growing from unsprouted seed was greater than that for plants growing from greensprouted plants which, in turn, was superior to that of transplants. This pattern was maintained through the season. Consequently, small advantages in time of emergence, such as that obtained with greensprouted-seed plants, were not accompanied by significant yield differences. Canopy size decreased as emergence was delayed and canopy size differences were determined largely by the amount of branching. As canopy size decreased and emergence was delayed, the net assimilation rate was found to increase.     

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.     

Effect of fumigation of potato seed tubers with 2-aminobutane on plant growth and yield

From 1968 to 1973, 13 field experiments were carried out to discover any effects of fumigation of seed tubers with 2-aminobutane (used for tuber disease control) on subsequent plant growth and yield. Nine experiments were done with tubers treated within 1 month of harvest, the remaining 4 with tubers stored for several months before treatment. In general, fumigation did not have any substantial effect on the growth pattern or the yield of the crop obtained from treated seed, although in most cases it was probable that there were small increases in the number of sprouting eyes, percentage emergence, stem number and in weight and number of seed tubers at harvest. However, these effects rarely reached levels which gave a statistically significant increase over crops grown from untreated material.     

Physiological age index: a new,simple and reliable index to assess the physiological age of seed potato tubers based on haulm killing date and length of the incubation period

Chronological and physiological age of seed tubers have major impacts on potato yields. This paper presents a new, simple and reliable physiological age index (PAI) that considers and reconciles the effects of chronological and physiological age. PAI calculation is based on the haulm killing date of the seed crop (T₀) and the end of the incubation period of seed tubers, measured under standardized conditions. The PAI formula is T₁/T₂, where T₁ is the time from haulm killing date (T₀) to possible planting date and T₂ the time from T₀ to the end of the incubation period. The PAI expresses physiological ageing of seed potato tubers within a range from 0 (for physiologically young) to 1 (old) tubers. To test the PAI existing data were re-evaluated and re-elaborated and specific experiments regarding seed origin and storage conditions for different cultivars were performed during 1994–1999. The PAI proved useful in assessing differences due to differences in growing conditions, cultivar, haulm killing, seed origin and storage system, and pre-planting treatments. For example, for cv. Spunta 6 days after haulm killing the PAI was 0.025 and after 100-storage days the PAI was 0.56, 0.52 and 0.49 for seed tubers stored in heaps in the field, at relatively high temperatures, natural diffuse light and a cold (4°C) and ventilated store, respectively. The PAI is related to ground cover duration and yield of the future crop. For a PAI of 0.55 tuber yield was 55 t ha⁻¹, while for a PAI of 0.80 tuber yield was 40 t ha⁻¹. The PAI is easy to measure, non-invasive, objective, reproducible and reliable and could be used for modelling purposes to describe performance of seed tubers.     

Ground cover, photosynthetic rate and tuber yield of potato (Solanum tuberosum L.) crops from seed tubers with different physiological age modified by foliar applications of plant growth regulators

Summary The modifying effects of applying the plant growth regulators (PGRs) benzylaminopurine (BAP), gibberellic acid (GA₃) and BAP+GA₃ on physiological age were studied. Two experiments with two cultivars, differing in rate of physiological ageing (medium-early Pampeana, medium-late Huinkul) and two storage systems were performed during 1988/89 and 1989/90 in two different potato areas of Argentina. In both seasons seed tubers stored in heaps reached an advanced physiological age at planting, compared with tubers from the cold store. Seed tubers of cv. Pampeana were older than those of Huinkul. compared with control crops, those sprayed with BAP maintained ground cover and photosynthesis for longer, and those sprayed with GA₃ for a shorter period. Consequently tuber yield was decreased by GA₃ in 1988/89, but in 1989/90 all crops treated with PGRs outyielded the control. BAP could overcome effects of advanced physiological age on crop senescence and tuber yield. CIC BA This work was carried out with a research grant from CAFPTA (249/89).     

Myzus persicae (Sulzer) in diffuse light and dark rustic storages and resultant PLRV transmission

Population levels ofMyzus persicae (Sulzer) were studied on potato tubers in diffuse light and dark rustic storage houses in Peru. No differences in numbers of aphids/sprouted eye on potatoes infested naturally during storage in diffuse light or darkness were observed. Significantly more alate aphids were observed on tubers stored in darkness than in diffuse light storage houses. Viral transmission was occurring during the storage period. The incidence of viral transmission was not significantly influenced by storing tubers in diffuse light or dark storages. There were significantly more plants infected with virus from tubers that had not been sprayed for aphid control than from tubers that had been sprayed     

Management of silver scurf (Helminthosporium solani) with fungicide seed treatments and storage practices

Thiabendazole insensitive strains ofHelminthosporium solani, the causal agent of silver scurf, make controlling the disease with seed treatment difficult. Potato tuber seed treatments and environmental storage management practices were investigated as means to minimize silver scurf. Fungicide seed treatments were evaluated for control ofH. solani; disease was evaluated during the growing season, at harvest, and after 5 months of storage. Silver scurf was observed on progeny tubers eleven weeks after planting. Fungicides that reduced silver scurf incidence and severity on the seed resulted in reduced incidence and severity of the disease in the progeny tubers at harvest and significantly lower disease ratings after storage. Only small increases in disease incidence (0-8%) were seen after storage. Thiophanate-methyl with mancozeb, Captan with mancozeb, and fludioxonil were among the most effective in reducing the incidence and severity of silver scurf on seed and in progeny tubers (Incidence on progeny tubers at harvest for these three treatments were 3%, 9%, and 8% respectively). Thiophanatemethyl alone was not effective for control of silver scurf (48% incidence compared to 43% incidence for the untreated control). Environmental conditions in storage affected disease development. Reduced humidity (85%) during the curing period (0–3 weeks after harvest) significantly reduced (11%) the surface area of tubers infected with silver scurf. Free moisture on the tuber surfaces during storage significantly increased (15%) tuber surface area infection.H. solani was shown to survive in soil and on some potato storage building materials for up to 9 months. The silver scurf disease of potatoes can be suppressed using effective seed treatment and storage management.     

Planting materials for warm tropic potato production: growth and yield of transplanted seedlings or rooted cuttings and tuber materials in the field

Expansion of potato production in lowland tropical regions has been constrained by the lack of planting materials, given that adapted genotypes and suitable field management practices now exist.

The respective performance of transplanted materials (i.e., true potato seed (TPS) seedlings or rooted stem cuttings) produced in situ in the warm tropics were compared with that of genetically identical seedling tubers (tubers produced from seedlings) or seed tubers. Seed and seedling tubers had been previously produced under optimal cool conditions. Transplanted materials achieved lower maximum leaf area index than did tuber materials (1.3–2.2 vs. 2.7) but relative growth rates of cuttings and seedlings were greater. This was in part due to the greater net assimilation rate of cuttings and to greater leaf:stem ratio for both compared with plants originating from tubers. Stolon and tuber formation were greater in seed tubers than in cuttings and in seedlings versus seedling tubers. On average, seedlings produced 14 tubers per plant, apical cuttings 12, seedling tubers 8, and stem cuttings 6.

Tuber yields within a genotype were statistically similar for crops from seed tubers or cuttings and for crops from seedling tubers or seedlings. However, the proportion of marketable (i.e., > 3.5 cm diameter) tubers was approximately 12% less in the crops from seed tuber and seedlings compared with those from cuttings and seedling tubers, respectively. Within a genotype, the crop duration in the field was similar whatever the type of planting material. Maximum yields, at 23 t/ha in warm sites, were still below those of temperate potato crops, but could be achieved equally well with transplanted in situ-produced materials or imported cool-climate seed tubers.     

Effect of Storage and Pre-sprouting Regimes on Seed Potato Performance in Norway

Physiological quality affects vigour and yield potential of potato seed tubers. Under short-season conditions, a seed tuber should preferably produce a short cycle and mature crop. The aim of the current studies was to assess how various storing and pre-sprouting treatments affect growth vigour and yield formation. Results showed that different low-temperature storage regimes before pre-sprouting treatments had no clear effects although some minor differences between treatments occurred. For pre-sprouted (‘green’-sprouted) seed tubers, results from field trials in southern Norway (2007–2008) showed that emergence of cvs Asterix and Saturna improved significantly compared to unsprouted seed. Total yields increased significantly for both cultivars in 1 out of 2?years. For Saturna, a major increase in number of tubers per plant resulted in larger proportions of smaller-size grades and thus lower marketable yields. In other trials (northern Norway, 2006–2007), varying duration of pre-sprouting did not affect growth vigour and yield. For number of tubers and size grades, the results varied significantly between pre-sprouting durations, but differently among trials, so no clear conclusions can be drawn. In one of the two trials, increased duration of pre-sprouting resulted in higher proportions of the smaller sizes at the expense of large tubers. Different levels of temperature sums during pre-sprouting (ca. 200 or 400?day-degrees >4?°C) did not affect seed performance. In conclusion, our studies showed that pre-sprouting may improve growth vigour and increase the proportion of smaller grade sizes.     

A method to assess cultivar differences in rate of physiological ageing of seed tubers

Inter-cultivar differences in rate of physiological ageing of potato tubers were assessed in a laboratory test and field tests. The physiological status of the seed tubers was varied by storing them at 4°C and a range of higher temperatures for 28 weeks (= excluding curing and pre-sprouting periods), after which tubers were desprouted. In a laboratory test, growth vigor was assessed by determining number and weight of sprouts after 28 days of incubation. In a field test, percentage emergence, total plant height, haulm and tuber weights were determined and a stand score was allocated 4 weeks after emergence of the 4°C storage treatment. Ageing indices were calculated by dividing the values for the warm-stored treatments by values for the tubers stored at 4°C. Using the tests the cultivars were scored from 0–10 and ranked accordingly. The indices were more evenly distributed over the range of 0–10 in the field test than in the laboratory test. Fresh haulm yield proved very suitable for calculating ageing indices but it could be replaced by a visual score of the haulm development without a great loss in accuracy     

Reduction of silver scurf on potatoes by pre- and post-storage treatment of seed tubers with imazalil

Control of silver scurf on daughter tubers was obtained by imazalil applied to seed tubers as a pre- or post-storage treatment or as a furrow treatment (at time of planting), in three field experiments. Post-storage and pre- and post-storage combination treatments provided consistent results. The most effective treatment in the first and second experiments was the combined pre- and post-storage application of imazalil. However, separate pre- and post-storage treatment also significantly reduced the incidence compared with the non-treated control. No differences were observed between dosages of 15 and 30 g a.i. of imazalil per ton of seed tubers. Although furrow treatment at planting time (1.5 1/ha) significantly reduced silver scurf incidence on daughter tubers, it was less effective than seed treatments. However, the combined treatment of pre-storage application and furrow treatment significantly reduced the disease and was more effective than the single pre-storage seed treatment. In the third experiment, a reduction of disease incidence and severity index was obtained by post-storage treatments or with the combination of pre- and post-storage applications.     

The effects of (S)-(+)-carvone treatments on seed potato tuber dormancy and sprouting

Summary Potato seed tubers may suffer from premature sprouting during storage, thus limiting their suitability for cultivation. Commonly used sprout suppressant treatments negatively affect but viability and therefore a reliable method to inhibit bud development must still be found for seed tubers. The monoterpene carvone ((S)-(+)-carvone) was tested in small scale experiments. The vapour of this compound fully inhibited bud growth of tubers cv. Monalisa stored at 23°C without affecting bud viability throughout 6 months of treatment. The most effective range of carvone vapour concentrations was between 0.34 and 1.06 μmol mol⁻¹. With these qualities we can expect carvone to become a suitable sprout suppressant for seed tubers.