Comparative performance of different-sized seed tubers derived from true potato seed

The growth and yield of plants from different-sized seed tubers derived from true potato seed were evaluated on a per stem, per plant, and per unit area basis using either single or multiple-sprout tubers. In single-sprout tubers, haulm dry weight per stem 47 days after planting was greater in the 40–60 g tubers when compared with that in the 5–10 g or the 10–20 g tubers. This resulted in greater tuber weight per stem in the 40–60 g tubers throughout the growing season. The number of tubers per stem was not affected by seed tuber size. In multiple-sprout seed tubers of increasing size, total tuber number and total tuber weight, as well as weight of those tubers larger than 45 mm, increased on a per plant basis but decreased on a per stem basis. At different rates of planting, 1–5 g seed tubers produced smaller tubers than 5–10 g or 10–20 g seed tubers. Increased rate of planting resulted in non-significant yield increases per unit area in plots planted with 1–5 g seed tubers. The yield increases were significant when 5–10 g and 10–20 g seed tubers were planted at higher rates. The number of main stems per unit of seed tuber weight was five times greater in 1–5 g tubers compared with that in 40–60 g tubers. This resulted in low seed weights per hectare when small tubers were planted and in a high ratio of harvested to planted tuber weight.     

Growth and yield of potato plants grown from microtubers in fields

Despite many reports of thein vitro production of microtubers, little is known about plant growth and yield from microtubers planted in the field. This study clarified differences in growth and yields between potato plants grown in the field from microtubers and from conventional seed tubers. The experiments were performed at Hokkaido University, Japan, over four years. Conventional seed tubers of about 50 g and microtubers of two sizes (0.5–1.0 g and 1.0–3.0 g) of the latematurity cultivar Norin 1 were planted, and plant growth and tuber yields were analyzed. The microtuber plants had a lower initial increase in root and leaf area index than conventional seed tuber plants, but had the same leaf area index after about 40 days from emergence. The first tuber formation in microtuber plants was about 7 days later than in conventional seed tuber plants, while tuber bulking occurred about 14 days later in microtuber plants. Consequently, the onset of tuber weight increase was later in microtuber plants, but the rate of increase thereafter was similar between conventional seed tuber and microtuber plants. At harvest the tuber fresh weight of microtuber plants was 82% that of conventional tuber plants, suggesting a potential for using microtubers for field planting.     

Rapid seed multiplication by planting into beds micro tubers and in vitro plants

Summary Micro tubers of 3 weight categories with means of 0.63 g, 1.25 g or 2.50 g and in vitro plants were planted in nursery beds at densities of 24 and 48 plants per m². The average tuber numbers and tuber weights were, respectively, 38% and 17% higher at 48 than at 24 plants per m². In vitro plants produced significantly more but smaller tubers than did plants grown from micro tubers. Plants grown from the larger micro tubers produced a similar number of tubers but larger ones than did plants grown from small micro tubers. Tuber yields and multiplication rates are discussed.     

Disease eradication and propagation of the initial seed potato material in Estonia

Summary The EVIKA Research Centre has developed a disease eradication system for the initial material of seed potato, which consists of 1. Selection of the initial material for eradication, plant thermotherapy, meristem tip cultivation and testing for viruses; 2. Re-eradication (thermotherapy of test-tube plants, cultivation of meristem tips, testing for viruses, testing of varietal quality and yield of disease-free meristem clones, and the selection of meristem clones with best varietal characteristics; 3. Renewing of the initial material (all processes as above, but the initial material is selected from the seed potatoes grown for at least 3 years in the field). Field trials were conducted after the second cycle of eradiaction to determine whether the plantlets were true-to-type and to assess the yield, disease resistance and tuber dry matter. Recently we have also started in vitro testing of meristem plants resistance to late blight, hoping that this approach will improve the selection efficiency. Propagation and growing of the seed tubers consists of 3 main steps: 1. Plantlet propagation in vitro; 2. Greenhouse propagation in plastic rolls; and 3. Planting the first generation tubers in the field. Under our conditions it is the cheapest, simplest and most effective way. Multiplication of the meristem-derived plants is done by shoot tip cuttings in a greenhouse in plastic rolls with peat as the growing medium. The first generation of seed tubers is grown in the field. In our trials plant productivity was affected by the method of multiplication, growing conditions and genotype. The highest yield per hectare was obtained with plants multiplied in plastic rolls. The in vitro plants had more tubers per plant than plants multiplied in plastic rolls. In seed production fields the productivity of plants was more influenced by following our instructions than by multiplication and growing methods. The number of tubers per plant obtained with over 0.5 million plants was 6.5–9.0. In the second generation of seed tubers, grown under equal density, the greater-sized tubers gave more tubers with lower weight than the smaller-sized tubers. Cutting tubers had no effect on the plant development and tuberization.     

Field performance of potato minitubers with different fresh weights and conventional seed tubers: Crop establishment and yield formation

Summary Field performance of five fresh weight classes of minitubers ranging from 0.13–0.25 g to 2.00–3.99 g and conventional seed tubers was studied in a short growing season (79 or 82 days) in two years. The heavier minitubers gave a more regular emergence, faster ground cover soon after emergence, higher dry-matter yields, and higher fresh tuber yields. Radiation conversion coefficient (RCC) did not differ. Higher tuber yields resulted from more radiation intercepted due to a faster ground cover, and a higher harvest index. All minitubers produced plants with one primary stem. In one experiment when heavier minitubers had long sprouts, time to 50% emergence decreased with tuber weight, whereas dry-matter concentration of progeny tubers increased. Conventional tubers appeared superior to minitubers in all characteristics mentioned except RCC, which was similar. Differences in performance between minitubers and conventional tubers were attributed to weight and age of seed tubers, presprouting method and crop husbandry.     

Soil water stress and the growth and yield of potato plants grown from microtubers and conventional seed tubers

Tuber yields of potato plants grown from microtubers in fields are more variable than yields from conventional seed tubers (CT). One reason could be their higher susceptibility to water stress. This study clarified the effect of soil water stress from 1 month after emergence on the growth and yield of plants grown from conventional seed tubers and microtubers in fields. Microtubers (0.5–3 g) and conventional seed tubers (50 g) were grown in Hokkaido, Japan, over three field seasons. One month after emergence, poly-shelters were placed over the plots to prevent rainfall, and either irrigated (wet plot) or non-irrigated (dry plot) treatments were formed. At mid-flowering (about 50 days after emergence) leaf area index (LAI) in microtuber plants was decreased relatively more due to soil water stress than LAI in conventional seed tuber plants. However, at maximum shoot growth (about 80 days after emergence) both microtuber and conventional seed tuber plants had a similar relative decrease in LAI due to soil water stress. At mid-flowering and maximum shoot growth microtuber and conventional seed tuber plants had reduced stomatal conductance due to soil water stress, but the reduction in stomatal conductance was greater in conventional seed tuber plants than in microtuber plants. Microtuber and conventional seed tuber plants had similar root development at maximum shoot growth. Tuber production from mid-flowering until plant maturity was similarly affected by soil water stress in microtuber and conventional seed tuber plants. At harvest, plants affected by soil water stress had about 87% of the tuber dry weight of irrigated plants. We conclude, that the greater variation on tuber yield of microtuber plants cannot be attributed to soil water stress from 1 month after emergence.     

Production and use of seedling tubers from true potato seed (TPS) for potato cultivation in Italy

Summary The effect of varying plant population on the production of tubers from potato seedlings was investigated during 1992 and 1993 using three different plant densities: 35, 70, 100 plants/m². Increasing the plant population significantly increased the number of tubers produced, but no significant difference was found between the plant densities of 70 and 100 plants/m². The seedling tubers produced in nursery beds were tested in the field for ware potato production using different sized tubers. The best performances were obtained using tubers 30–40 mm. Significant differences were evident among the 7 true potato seed (TPS) families used, but data grouped by type of cross did not indicate any significant difference between 4X×4X and 4X×2X crossing groups.     

Field performance of potato minitubers with different fresh weights and conventional seed tubers: Multiplication factors and progeny yield variation

Summary Multiplication factors and progeny yield variation in crops from minitubers of five weight classes (ranging from 0.13–0.25 g to 2.00–3.99 g) and conventional seed tubers were studied in field experiments in three years. Multiplication factors were calculated as the number and weight of progeny tubers produced per planted tuber or per unit planted tuber weight. They were lower for the lighter minitubers when calculated per tuber and higher when calculated per weight. Yield variation was described by coefficients of variation for the number and weight of progeny tubers produced. Variation over individual plants of a crop was higher in stands from the lighter minitubers. Variation over plots within a field was sometimes higher for the lighter minitubers, but variation over years was similar for all minituber classes. Variation over plots in progeny tuber weight was higher for minitubers than for conventional tubers.     

Effect of gibberellic acid and multiple harvests on production and reproductive value of seed potatoes produced above ground on stem cuttings

Summary Potato plants of cvs Eersteling and Bintje were grown from stem cuttings and induced to form aerial tubers for use as seed. Spraying the plants with gibberellic acid in concentrations of 10, 25 and 50 mg/l to induce stolon formation in the leaf axils led to a decrease in the number of tubers formed per plant. Multiple harvesting of the largest tubers from plants treated with gibberellic acid or not, approximately doubled the number of tubers formed but halved their individual weight compared with only one harvest at plant senescence. After a storage period of about 1 year, with their vigour declining, the aerial tubers were planted in the field. Aerial seed tubers taken from multiple harvests during the previous year produced the same number of tubers as plants grown from above-ground tubers harvested at plant senescence only, but the tuber yields declined with earlier harvesting when small (5–13 mm) aerial tubers were used, compared to larger (14–19 mm) tubers.     

Effect of production temperature of seed potatoes on subsequent yielding potential

A two year experiment was conducted to test if the temperature environment under which seed potatoes are produced significantly affects the tuber development and yield of the resultant potato plants. Six temperature regimes were established in the controlled facility of the Biotron. Two generations ofSolanum tuberosum ‘Kennebec’ tubers were grown in these environments and the yielding ability of plants produced from these tubers was tested in greenhouse facilities. Plant growth and tuber yields were similar to those which might be expected under field conditions, and marked differences in the development and productivity as a result of the production environment of the seed tubers were apparent. However, no evidence was found to support the contention that seed potatoes originating from cooler environments had any increased potential to produce higher yielding plants than comparable seed from warm environments. Even within a generation, the highest yields were found in the warmest environments, somewhat modifying the concept that the potato is strictly a cool-season crop. Other possible non-pathogenic explanations for previously observed differences in seed quality as a result of the production environment are discussed.     

Growth and yield of potato (Solanum tuberosum L.) cultivars Atlantic and Monona as influenced by seed type and size

Growth and yield of potato plants grown from several weight classes of whole “B” seed, unsorted “B” seed, and 56 g cut seed pieces were compared in Ohio in 1988 and 1989. Whole “B” seed classes were 8 g ranges with means of 35 g, 43 g, 51 g, and 58 g. Unsorted “B” seed was used as an experimental control. Treatment responses were inconsistent. Few significant differences were evident at bloom in leaf area, number of main stems, and total plant dry weight (without tubers) per hill. However, the number of tubers greater than 1 cm in diameter per hill at bloom was less for cut seed as compared with several whole seed treatments. Percent stand at four weeks was also less for cut seed compared with 51 g and 58 g whole tuber treatments. Significant differences in total and U.S. No. 1 yields were absent despite differences in several plant growth variables early in the 1988 and 1989 growing seasons.     

Morphological changes and yield enhancement of superior potatoes by AC 243,654

AC 243,654, 1-(m)-methoxybenzyl)-3-nitroguanidine, represents a new family of plant growth regulators with cytokinin-like activity. This compound was tested at 1 and 4 kg/ha on greenhouse-grown potatoes (Solanum tuberosum L.), cultivar Superior. The treatments were applied two weeks after emergence. Morphological and yield effects of AC 243,654 were determined at 4, 7, 11, 14, 21, 42 and 70 days after treatment (DAT). Shortly after treatment, AC 243,654 stimulated plant height, branch number and stolon number. Plant weights were initially stimulated. At the final harvest, 70 DAT, the dry weight of treated plants was greater than that of the check plants; this is attributed to the anti-senescence effect of this compound on vine tissue. AC 243,654 induced tuber initiation at 14 DAT, whereas checks did not have tubers until one week later. Between 14 and 70 DAT, treated plants produced greater yield than check plants; the yield increases were primarily due to larger tubers. The yield of smaller tubers was decreased by the treatments. Although the number of larger tubers increased, total tuber number was decreased by AC 243,654. Observations on tuber number over time suggested that the check plants initiated more tubers than treated plants but most of these aborted. In treated plants, less tubers were initiated.     

The quality of seed tubers multiplied in the Golan Heights for the spring season in Israel

Summary Seed tubers grown in the northern mountain region — the Golan Heights — were as productive as imported seed tubers. In cvs. Blanka and Désirée, both the locally grown and the imported seed tubers were similar when yield components and tuber fresh weight are considered. In Up-to-Date, the locally grown seeds produced higher yields of marketable tubers (over 60 g/tuber) than those imported. Désirée seed tubers grown for two generations in the Golan Heights did not differ significantly in their productivity as compared with common Golan seeds and with imported ones. Seed tubers harvested from plots which were protected by means of white coarse nets and weekly sprays with insecticides, were virtually virus-free and were used for growing commercial seeds in the Golan. The use of this method for seed multiplication is suggested. Contribution from the Agricultural Research Organization. The Volcani Center, Bet Dagan, Israel. No 137-E, 1981 Series.     

Varietal differences in the response of potatoes to repeated short periods of water stress in hot climates. 2. Tuber yield and dry matter accumulation and other tuber properties

Summary The effect of repeated short periods of water stress during the hot season on six potato cultivars was investigated. The number of tubers per plant tended to decrease in response to water stress in cultivars which had more than 9.8 tubers per control plant (Désirée, Alpha, Elvira). In the other cultivars, no consistent effect of water stress on tuber number per plant was observed. Except for Spunta, the percentage of large tubers (>60 g/tuber) was reduced in the water-stressed plants. Consequently, the average weight of these tubers was greater than that of tubers harvested from the unstressed plants, indicating that the sink force of the individual tuber was not impaired by drought. However, tuber yield per plant was reduced due to drought in all cultivars tested. The smallest decrease in dry matter accumulation as well as the greatest lowering of the osmotic potential in the tuber tissue was found in Alpha. No consistent effect of water stress on the percentage of misshapen and sprouting tubers was observed, indicating the marked effect of the high temperature on these traits. Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, No 310-E, 1981 series. This investigation was sponsored by a grant from the Ministry for Development Cooperation of the Netherlands.     

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.     

Hill to hill variations in tuber yield of potatoes in Alberta

The hill to hill variation in tuber yield and mainstem number was studied on 18 potato farms. There were up to 14-fold differences in the tuber yield per hill among plants of Norland, Russet Burbank, Norchip, Carlton and Alaska Red. The mainstem number was more variable than tuber weight per hill in Norland, Russet Burbank and Alaska Red. However, the opposite was true in Norchip and Carlton. In nearly all comparisons, the number of tubers per hill was less variable than tuber weight and mainstem number per hill. The total variation in tuber weight found in about 50% of the samples could be explained by the variance of hills within rows. Even in samples where an added variance component due to differences among rows was present, relatively more variation occurred within than among rows. The correlation coefficients between the number of mainstems and tuber weight per hill were positive but significant (P&< 0.05) only in Norland and Norchip. The correlation coefficients between the number of mainstems and number of tubers per hill were also positive but slightly higher and significant (P<0.01) in all 5 cultivars. The coefficient of determination values indicated that variation in cut seed piece weight explained only about 10% of the total variation in tuber weight harvested per hill. At a spacing of 30 cm within the row, a major proportion of hill to hill variation in tuber yield had to be explained by factors other than the seed piece weight.     

Effect of cultivar maturity period on the growth and yield of potato plants grown from microtubers and conventional seed tubers

Potato plants of early cultivars grown from microtubers have been reported to have a much lower growth vigor and produce lower yields than microtubers of late cultivars. This study intended to clarify the field performance of plants grown from directly planted microtubers of cultivars with different maturity periods, with a special attention to early cultivars. The experiments were conducted at Hokkaido University, Japan, over four years. Microtubers and conventional seed tubers of the early cultivar Kitaakari, late cultivars Konafubuki and Norin 1, and very late breeding line IWA-1 were planted, and the plant growth and tuber yields were analyzed. The microtuber plants of Kitaakari had a lower initial increase in leaf area index than conventional seed tuber plants, but at the maximum shoot growth had the same leaf area index. This pattern was also observed in the other cultivars. Tuber initiation and tuber bulking occurred on average five days later in microtuber plants than in conventional seed tuber plants of cultivar Kitaakari. At maximum shoot growth, microtuber plants had on average 65% of tuber dry weight of conventional seed tuber plants, with small variation among cultivars. Irrespective of maturity period, microtuber plants showed a higher tuber increase after maximum shoot growth, achieving around 86% of tuber dry weight of conventional seed tuber plants at harvest. From the results of this study we conclude that microtuber plants of early and late cultivars have a similar yield potential relative to conventional seed tuber plants, and microtubers of both early and late cultivars might be used as an alternative seed tuber source for potato production, if necessary.     

Contamination of soil and transmission of seedborne potato dry rot fungi (Fusarium spp.) to progeny tubers

A survey of selected potato soils in Maine was made to determine the species and populations ofFusarium spp. present.Fusarium solani ‘Coeruleum’ was most often isolated butFusarium roseum ‘Sambucinum’ was not recovered from any soil. Crops or cropping sequences in general showed no direct relationship to observed Fusaria populations or tuber dry rot. Field studies were conducted to determine the effect ofFusarium contaminated seed on soil and daughter tuber contamination. Whole and cut seed were inoculated withFusarium roseum ‘Sambucinum’ and half of each lot treated with thiabendazole (1500 ppm) to controlFusarium seed decay. Soil populations ofF. roseum ‘Sambucinum’ were higher near plants produced from non-treated, cut seed tubers. No increase inFusarium populations was found between plants or near plants produced from whole or thiabendazole treated seed. Daughter tuber contamination was greatest from plants produced from non-treated contaminated cut seed, and lowest from whole or treated seed. Whole non-treated seed produced daughter tubers with contamination equal to treated whole seed. This indicates that the use of whole seed could be a method to reduce daughter tuber contamination and reduce reliance on chemical treatments. Cut seed contaminated withFusarium spp. is an important source of daughter tuber contamination which can result in a high amount of tuber dry rot in storage.     

The effect of density on tuber yield in plants grown from true potato seed in seed beds during two contrasting seasons

The production of potatoes from true seed was studied in direct-sown seed beds during both winter and summer seasons in Lima, Peru. After emergence, seedlings were thinned to give 6, 12, 24, 48 or 96 plants per m². In all five density treatments plants were arranged in a square configuration. In both seasons, increasing plant density significantly increased total tuber number as well as tuber weights in the grades 1–5 g, 5–20 g and 20–40 g. The yield of tubers larger than 40 g was similar in all densities. In the warm summer season, tuber number was significantly reduced and mean tuber weight was 56% greater compared with that in the winter season. The potential of producing consumer potatoes from true seed in seed beds in warm climates is discussed.     

Variation in the duration of tuber dormancy within a seed potato lot

Summary The variation in duration of dormancy within a seed tuber lot was studied over three years by harvesting individual plants of cvs Diamant and Désirée from field plots and by storing the tubers at 18°C. The variation in dormancy within a tuber lot was large (especially for cv. Diamant) and was mainly caused by variation within plants. For cv. Diamant there was a close negative relation between dormancy and the cube root of tuber weight, whereas for cv. Désirée a relation with tuber weight was almost absent. The duration of dormancy of a seed lot comprising tubers with a narrow range in weight can be well described by two parameters. It is proposed to maintain the moment of 80% sprouting as the criterion for the end of dormancy of a tuber lot and to characterize the spread in dormancy duration by the time lapse between 10% and 90% sprouting.