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.     

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.     

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.     

Comparative performance of three small seed tuber sizes and standard size seed tubers planted at similar stem densities

Summary Small seed tubers of 1–5 g, 5–10 g and 10–20 g were planted at the same sprout densities as standard size seed tubers of 40–60 g in order to give similar stem densities. Early ground cover by foliage, total yield, and yield of tubers >45 mm were consistently greater in plots planted with larger seed tubers. The effect of seed tuber size on yield and tuber number per stem varied between years but 1–5 g seed tubers always gave lower yields per stem than larger seed tubers. Reducing the spacing between rows from 90 cm to 60 cm and maintaining the same sprout density was more effective in increasing yields from small seed tubers than increasing sprout density from 20 to 40 sprouts per m² by reducing plant spacing within the row.     

Inter-stem and inter-tuber competition in potatoes

Summary Seed pieces of varying size and bearing different numbers of uniform growing sprouts were planted in specific combinations. Sequential harvests were made and the growth of the plants followed. There appeared to be competition between emerging sprouts for nutrients and water from the soil. This competition influenced the number of stems produced per sprout and the size attained by these stems. There was no effect of size of the seed piece on the apparent time to tuber initiation. A constant number of tubers were formed per stem despite large variations in stem size, but the final weight of tubers per stem was lower the greater the number of stems per hill. The number of tubers larger than 2| inches (5.7 cm) remained constant over the whole range of stem numbers per hill and the mean weights of tubers in the two size categories larger than 1| inches (3.2 cm) remained constant after the second harvest. These results suggest that only a few of the tubers in each hill were growing rapidly at any one time. There was no effect of cutting the seed tubers on any aspect of the growth of potatoes that was measured which could not be attributed to an effect on either the size of the seed piece or on the number of sprouts per seed piece.     

Interrelationships of the number of initial sprouts,stems, stolons and tubers per potato plant

Summary The relationships between the number of initial sprouts, the number of main stems, stolons and tubers per plant are depicted in 4-quadrant figures. The number of sprouts per seed tuber varied because of different pre-sprouting conditions and/or because of the use of different cultivars. Good linear relationships are shown between the numbers of sprouts and stems, stolons and tubers, and sprouts and tubers, but especially between stolons and tubers within each trial with the one cultivar. When comparing different experiments with the one cultivar the linear relationship between the numbers of stems and stolons disappeared. When comparing different cultivars, no relation was found between the numbers of sprouts and stems. These two cases also led to a statistically less significant relation between the number of sprouts planted and the number of tubers harvested.     

Morphological changes in tuber buds during dormancy and initial sprout growth of seed potatoes

Summary Potato tuber dormancy is usually defined as lasting from tuber initiation until a sprout of 2 mm long has been formed under storage conditions optimal for sprouting. We tried to find out whether there is a period during which buds of seed tubers do not grow and whether different batches of seed take the same time to grow sprouts 2 mm long. We measured changes in number of leaf primordia and length of tuber buds of cvs Diamant and Désirée over two years. After early haulm pulling, buds did not grow for at least 60 days (‘Diamant’) or 95 days (‘Désirée’). Buds in both cultivars and two tuber weights of ‘Diamant’ took about 20 days from the estimated onset of sprouting to grow 2 mm long. We question whether this period is always similar and thus whether the moment sprouts 2 mm long have formed is a good criterion for the end of dormancy.     

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.     

马铃薯种薯芽条根原基的发生与发育过程的解剖观察

对种薯芽条根原基的切片观察发现:根原基发生在芽条上各侧芽原基附近,由靠近形成层的一团薄壁细胞再分化形成,属内生源;每节约有3～6个根原基,成对地分布在侧芽原基的上、中、下3个部位,中部的1对根原基先发生且较长;芽条上的根原基一般依由基向顶的顺序发生,但基部1～2节的发生较晚,尤其是在用高浓度GA处理切块的芽条中;基部几节的根原基往往在栽种到大田后才发生,芽条越长根原基的数目越多、越长,当长度大于2cm时,根原基已接近或突破表皮,这是催大芽可提早出苗的基础;根原基的分化和伸长可能与芽条生长速度有关。     

Factors influencing time to breakdown (TTB) of cooked potato tissue

Cooking ability or time-to-breakdown (TTB) of different portions of potato tubers was determined by taking cores 1.27 cm (1/2inch) in diameter and 0.95 cm (3/8 inch) long from 12 locations in the tubers and cooking until penetration of a weighted rod pressing on the cores. Cores from the stem portion, on the average, required over twice as long for penetration of the rod during cooking as compared to cores from the bud section. The cores from the middle longitudinal portion of the tuber took longer to cook than cores from either side. Low specific gravity (1.070) tubers took significantly longer to cook than cores from high specific gravity (1.090) potatoes. However, when specific gravity of individual cores was determined with a pycnometer and TTB determined for the same samples, no relationships could be established. Cores from the stem portion took longer for TTB regardless of specific gravity or starch content. The data suggested much greater influence of cell wall structure as would be obtained from different portions of the tuber on TTB than starch content of the cells. No differences in TTB were obtained from tubers of high or low fertility or between Norgold Russet and Russet Burbank varieties, except Norgold was more uniform in cooking time between the stem and bud portion than Russet Burbank.     

马铃薯纺锤块茎类病毒不同株系及不同接种方法对产量的影响

马铃薯纺锤块径类病毒(Potato spindle tuber viroid)是危害黑龙江省马铃薯生产的一种重要病害。为了查明不同类病毒变株对主栽品种克新1号和4号所引起的产量损失和症状反应,应用往复聚丙烯胺凝胶电泳法(Peturn-Polyacmdegel electophoresis)鉴定类病毒。试验结果表明,接种当年,接种类病毒的处理平均减产37%,按商品产量计算减产达47%。当年表现症状的植株平均为59.6%,块茎产生症状的植株平均为57.4%。用于接种的3个马铃薯纺锤块茎类病毒变株的致病力,以当地的类病毒弱系为最强,其次为北美的类病毒强系,北美的类病毒弱系的致病力较弱。类病毒对产量的影响与马铃薯品种和类病毒变株的组合有极为密切的关系。克新1号接种当地的类病毒弱系时薯块严重畸变,商品产量只为不接种对照的21%。用往复电泳法检测各个试验处理被类病毒侵柴的情况,芽接种处理,于出苗后1周即可检测到类病毒,叶接种处理,于接种后2周即能检测到类病毒。出苗后7周,植株中类病毒浓度达到高峰,随即急剧下降,到出苗后10周,大部分接种植株已检测不到类病毒。块茎直径达1厘米时,即能检测到类病毒,随着块茎膨大,类病毒浓度也相应增高,到收获前,块茎中的类病毒含量只略低于植株含类病毒高峰期的浓度。用于本试验的克新1号、4号无类病毒和主要马铃薯病毒的核心材料,在1988年已交付给省内外的良种场繁殖使用。于当年秋季抽样检测克山第二良种场连续种植二年的种薯,当年种植试管苗生产的种薯,以及试管苗等,均未检测到类病毒。     

An agro-economic assessment of seed-potato storage technologies in the Philippines

A series of 14 on-farm trials indicated that improved seed-storage facilities, in the form of additional diffuse light and ventilation, may considerably reduce losses of seed-tubers and result in a better quality product: less weight loss in store, more sprouts per tuber and shorter, more robust, sprouts. This improvement resulted generally in improved emergence, stem number per hill, yield of marketable tubers and economic return. The improved onfarm stores compared favourably with the refrigerated storage available locally.     

Microtuber and minituber production and field performance compared with normal tubers

Summary Microtuber and minitubers of cv. Monalisa were produced in the laboratory and compared with normal seed tubers in a field experiment. These tubers were planted at similar plant densities (13.6 sprouts per m²) with two distances between rows (60 and 90 cm). Final ground cover was almost complete only in the plots derived from normal tubers and decreased with the size of the mother tubers. Normal seed, mini- and microtubers yielded respectively 50.8, 31.7, and 17.0 t/ha (means of two spacings). At close and wide spacing between rows, microtubers yielded respectively 27.3 and 6.7 t/ha, and minitubers 38.9 to 24.4 t/ha. Row spacing did not influence the yields from normal seed tubers. Total number of tubers per m² was also affected and, as means of the two spacings, ranged from 107.8 with microtubers, 122.1 with minitubers, to 142.9 with normal tubers. Mother tuber type also affected the yield distribution in three tuber grades (<36, 36–55, and 55–80 mm) and micro and minitubers produced many small tubers. Multiplication rates and the possible use of different propagation sources are discussed.     

How Planting Density Affects Number and Yield of Potato Minitubers in a Commercial Glasshouse Production System

Commercial potato minituber production systems aim at high tuber numbers per plant. This study investigated by which mechanisms planting density (25.0, 62.5 and 145.8 plants/m²) of in vitro derived plantlets affected minituber yield and minituber number per plantlet. Lowering planting density resulted in a slower increase in soil cover by the leaves and reduced the accumulated intercepted radiation (AIR). It initially also reduced light use efficiency (LUE) and harvest index, and thus tuber weights per m². At the commercial harvest 10 weeks after planting (WAP), LUE tended to be higher at lower densities. This compensated for the lower AIR and led to only slightly lower tuber yields. Lowering planting density increased tuber numbers per (planted) plantlet in all grades. It improved plantlet survival and increased stem numbers per plant. However, fewer stolons were produced per stem, whereas stolon numbers per plant were not affected. At lower densities, more tubers were initiated per stolon and the balance between initiation and later resorption of tubers was more favourable. Early interplant competition was thought to reduce the number of tubers initiated at higher densities, whereas later-occurring interplant competition resulted in a large fraction of the initiated tubers being resorbed at intermediate planting densities. At low planting densities, the high number of tubers initiated was also retained. Shortening of the production period could be considered at higher planting densities, because tuber number in the commercial grade > 9 mm did not increase any more after 6 WAP.     

Post-harvest characteristics of potato minitubers with different fresh weights and from different harvests. I. Dry-matter concentration and dormancy

Summary Dry-matter concentration and dormancy were studied in minitubers of cvs Agria and Liseta, using five fresh weight classes (<0.50 g, 0.50–0.99 g, 1.00–1.99 g, 2.00–2.99 g and ≥3.00 g) and three successive harvests of the same plantlets. The average dry-matter concentration increased with tuber weight for tubers from the second and third harvests. In minitubers ≥0.5 g, dry-matter concentration was higher in tubers from later harvests. The dormant period (days from harvest to 50% sprouting) was longer in minitubers with lower than higher weights, and longer in tubers from the first harvest than from later harvests. A cold-storage period of 6 weeks, starting 14 days after harvest, reduced the dormant period by an average of 11 days.     

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.     

株行距和施肥量对木薯产量及生长的影响

采用裂区试验设计方法,研究株行距和施肥量对华南5号木薯产量和生长的影响.结果表明:在本试验株行距和施肥量条件下,施肥量对木薯产量和生长的影响比株行距大.密植(0.6～0.8 m)有利于提高淀粉产量、鲜薯产量和鲜薯淀粉含量,以0.8m株行距最佳,而疏植(1.2～1.4m)有利于提高单株薯数、单株鲜薯重、单株鲜茎叶重、收获指数和茎径.施肥有利于提高淀粉产量、鲜薯产量、单株鲜薯重、单株鲜茎叶重、茎径、株高和单株薯数,但降低鲜薯淀粉含量和收获指数.丰产栽培技术要兼顾单位面积株数、单株鲜薯重和鲜薯淀粉含量.建议在土壤肥力差和少施肥时,用0.6 m株行距;土壤肥力中等且较高施肥时.采用0.8 m株行距;土壤肥力中上且优越水肥管理,采用1.0 m株行距.     

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     

Tuber initiation and development in irrigated and non-irrigated potatoes

Tuber initiation and development are processes basic to potato production and are particularly critical in areas with short growing seasons. It is important to know how and to what extent management decisions affect these processes in order to maximize the yield of marketable tubers. A two-year field study, conducted in southcentral Alaska, examined top growth, tuber initiation, and tuber development in eight potato cultivars grown with and without irrigation. Plants of the cultivars Allagash Russet, Bake-King, Green Mountain, Kennebec, Lemhi Russet, Russet Burbank, Shepody, and Superior were harvested weekly throughout the growing season, and top dry weight, numbers of tubers, and individual tuber fresh weights were recorded. Top dry weight was reduced by moisture stress shortly after emergence in 1993, and about one month following emergence in 1994, when early-season soil moisture was greater. The weight of tubers was similarly affected within approximately 5 wk of emergence in 1993 and 6 weeks in 1994. Tuber weight at harvest was increased two-to three-fold by irrigation in all cultivars. The number of tubers each plant set was affected by irrigation in most, but not all, cultivars. Some varieties (Lemhi Russet in 1994, Allagash Russet both years) set more tubers than were maintained through the growing season. Tuber remnants found during sample collection indicated that tuber reabsorption had occurred. Irrigated Green Mountain had more than one tuber initiation period during the season, whereas other varieties such as Shepody maintained a relatively constant number of tubers following initial tuber set. Tuber size distribution at the end of the growing season showed that larger tubers were favored by irrigation.     

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.