Growth of early potatoes from different portions of seed tubers I. Emergence and plant stand

Several of the recently released early potato cultivars in Ontario are prone to poor and/or uneven stands. Studies were undertaken to investigate these problems. Basal seed halves of Jemseg and Yukon Gold were found to emerge an average of 4.6 and 5.7 days, respectively, later than shoots from apical halves or whole tubers in 3 years of study. No practical difference in emergence was found among tuber portions of Superior. Sums of squares attributed to seed portions accounted for 51.1 percent of the variation of days to 50 percent emergence for Jemseg, 50.3% for Yukon Gold and 8 percent for Superior. No difference in final percent emergence was found among the various seed portions of Jemseg and Superior. Cultivars with strong apical dominance or dormancy appear prone to uneven emergence.     

A method of producing seed tubers from true potato seed

Summary First-generation seed tubers (seedling tubers) derived from true potato seed (TPS) were produced in nursery beds; the yields were up to 12 kg and total numbers up to 1242 tubers (>1 g) per m² of bed. Direct sowing of TPS in beds followed by thinning gave yields similar to those from transplanted seedlings and reduced the total growing period. The optimum plant population was 100 plants per m² spaced at 10 cm×10cm. The application of 3 cm of substrate (1∶1 shredded peat moss:sand) after seedling emergence was sufficient to maximize tuber number and to minimize tuber greening. Two or three applications of N-dimethylaminosuccinamic acid (B9) gave sturdier plants but did not increase the number of tubers >1 g. The seedling tubers when multiplied gave yields similar to those of low virus clonal seed tubers. The potential use of this method by farmers in developing countries is discussed.

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Zusammenfassung Für den Kartoffelanbau erscheint die Verwendung von Pflanzkartoffeln, die von Samenkartoffeln (TPS) stammen, als besonders geeignet, weil hier die niedrigen Kosten und der hohe Gesundheitsstandard der TPS vereinigt werden k?nnen mit der gewohnten Handhabung und der schnellen Pflanzenentwicklung bei Pflanzkartoffeln. Die von den TPS stammenden Knollen der ersten Generation (S?mlingsknollen) wurden in Beeten von 1,1 m Breite und 0,25 m Tiefe erzeugt, die mit einer 1∶1 Mischung aus zerkleinertem Torf und Sand gefüllt waren. Ein Vergleich zwischen der direkten Aussaat der TPS in die Beete mit nachfolgendem Ausdünnen und dem Umpflanzen von S?mlingen in die Beete ergab bei der Reifeernte die gleiche Gesamtzahl an Knollen und Ertr?gen (Abb. 1). Die gesamte Wachstumsperiode von der Aussaat an betrug bei der direkten Aussaatmethode 110 Tage, bei der Verpflanzungsmethode aber 125 Tage wegen des dem Umpflanzen nachfolgenden Wachstumsschocks. Die Zunahme der Pflanzenzahl erh?hte den Anteil des mit Bl?ttern bedeckten Bodens (Abb. 2), verringerte die überlebensrate der Pflanzen (Tabelle 1), erh?hte den Knollenertrag und die Anzahl der Knollen, die kleiner oder gr?sser als 1 g waren (Abb. 3) und verringerte nicht die Knollenzahl in einer der Gr?ssenklassen (Abb. 4). Die optimale Pflanzendichte war 100 Pflanzen/m² in Abst?nden von 10 cm × 10 cm; eine gr?ssere Pflanzdichte behinderte das Anh?ufeln. Die Anwendung von 2–3 cm des 1∶1 Torf-Sandgemisches nach dem Auflaufen der S?mlinge f?rderte die Stolonenbildung und erh?hte die Anzahl und das Gewicht der Knollen >1 g im Vergleich zur Kontrolle (Tabelle 2). Bei der Anwendung von 6–7 cm Substrat unterschied sich die Stolonen-und Knollenbildung nur wenig von derjenigen mit 2–3 cm. Die Applikation von N-Dimethylaminobernsteins?ure (B9) ergab kr?ftigere Pflanzen sowie weniger und kürzere Stolonen (Tabelle 3). Die Applikation bei Pflanzenh?hen von 10 und 15 cm beeintr?chtigte nicht die Knollenzahl oder den Ertrag, w?hrend Applikationen bei Pflanzenh?hen von 8, 12 und 20 cm die Anzahl der Knollen, die kleiner als 1 g sind, um 73% erh?hte und das Gesamtgewicht der Knollen, verglichen mit der Kontrolle, verringerte. Die S?mlingsknollen >1 g wurden in bew?sserten Feldern mit einem durchschnittlichen Multiplikationsfaktor (Verh?ltnis zwischen dem gepflanzten und dem geernteten Gewicht) von 22 vermehrt. Eine 10 m² grosse Anzuchtfl?che k?nnte genügend Knollen erzeugen, um nach 3 aufeinanderfolgenden Vermehrungen 200 t Pflanzkartoffeln zu erhalten. Vermehrte S?mlingsknollen der Linie DTO-33 die von offen best?ubten TPS stammten, ergaben gleiche Ertr?ge wie die virusarmen Pflanzkartoffeln des Klones DTO-33. Die Methode, S?mlingsknollen in Anzuchtg?rten zu erzeugen, k?nnte die Landwirte in den Entwicklungsl?ndern in die Lage versetzen, ihre eigenen Pflanzkartoffeln zu produzieren.

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Résumé L'utilisation de plants issus de semences vraies (TPS) semble être une méthode efficace pour la culture de la pomme de terre, car elle associe à un faible co?t un niveau sanitaire élevé des semences vraies, ainsi qu'une facilité de manutention et un développement rapide des plantes à partir des tubercules de semence. La première génération de tubercules (tubercules issus de plantules) provenant de semences vraies a été plantée en billons d'1.1 m de large et 0.25 m de profondeur, remplis d'un mélange 1∶1 de tourbe fragmentée et de sable. Un semis direct suivi d'un éclaircissage, comparé à un repiquage de plantules dans les billons, donne un nombre total de tubercules et un rendement à maturité identique (fig. 1). La période de végétation à partir du semis était de 110 jours mais atteint 125 jours avec la méthode de repiquage, à cause d'un retard de croissance après plantation. L'augmentation conduit à un recouvrement du sol plus rapide par le feuillage (fig. 2), à une diminution de la survie des plantes (tableau 1), à un rendement en tubercules plus important, à un nombre plus élevé de tubercules inférieurs ou supérieurs à 1 g (fig. 3), tandis que le nombre de tubercules par calibre ne diminue pas (fig. 4). La densité optimale est de 100 plantes par m² espacées de 10 cm × 10 cm. Une population plus dense empêche le buttage. Un apport de 2–3 cm du mélange tourbe-sable après la levée de plantules favorise la formation des stolons et augmente le nombre et le poids des tubercules inférieurs à 1 g par rapport au témoin (tableau 2). Un apport de 6–7 cm de substrat donne peut de différence au niveau de la formation des stolons et des tubercules, par rapport à 2–3 cm. Une application d'acide N-dimethylaminosuccinamique (B9) donne des plantes plus vigoureuses et moins de stolons et de longueur plus courte (tableau 3). Une application réalisée au stade 10–15 cm des plantes n'affecte pas le nombre de tubercules ni le rendement, tandis que des applications à 8, 12 et 20 cm augmentent de 73% le nombre de petits tubercules inférieurs à 1 g et diminuent le poids total des tubercules par rapport au témoin. Les tubercules supérieurs à 1 g issus de semences sont multipliés en parcelles irriguées avec un coefficient de multiplication 22 (rapport entre poids récolté et poids planté). 10 m² de surface de multiplication peut produire un nombre de tubercules suffisant pour atteindre 200 tonnes de plants après 3 multiplications successives. Les tubercules obtenus par multiplication à partir de semences vraies de la lignée DTO-33 ont donné des rendements similaires à des plants indemnes de virus issus du cl?ne DTO-33. La méthode de production de plants à partir de semences peut permettre aux producteurs des pays en voie de développement de produire leur propre plant.

     

On-farm evaluation of true potato seed in the Philippines

Potato production using true potato seed (TPS) was evaluated with a cooperative group of farmers. The cooperative grew TPS or seed tubers (1 to 3 g) produced from TPS in beds in screenhouses to avoidPseudomonas solanacearum (BW). From 250 to 400 tubers/m² were obtained. Tubers > 3 g were replanted by farmers at high elevation for further multiplication. Yields always exceeded the control (clonally produced cultivar). Seed tubers from TPS of 3 to 5 g produced up to 32 t/ha resulting in a multiplication rate of 145:1. Farmers are in various stages of adopting this technology. An early maturing progeny with resistance to BW is needed to permit a more rapid spread of this technology.     

Osmotic priming of true potato seed: Effects of seed age

Summary The effects on germination and early seedling growth of presowing true potato seed in water or gibberellic acid (GA) at 1500 ppm and of priming in −1.0, −1.25 and −1.5 MPa solutions of KNO₃+K₃PO₄ were studied using 30, 18, 6 and 3/4 month-old seed. The influence of light during presowing on the effectiveness of treatments was also investigated. Overall, priming in the light at −1.0 MPa was the most, and GA the least successful treatment for enhancing emergence and subsequent seedling growth. Though GA increased final emergence from about 20 to 70% in the most recently harvested lot (3/4 mo), the rate and extent of final germination or emergence in this dormant seed was still much lower than that of the nondormant lots (6–30 mo), especially when the latter were primed. For all lots, dry weight per seedling was 40% lower in dormant than in nondormant seed, and 20% higher when seeds were primed at −1.0 MPa than when GA treated. In conclusion, the use of nondormant seed may be a requirement for both effective priming and sowing of potato crops via true seed.     

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.     

Engineering needs for potato production from true seed

Potatoes grown from true potato seed (TPS) are generally small and nonuniform in size and shape, compared to the ones produced conventionally from seed tubers. Potato production from TPS would be considerably less expensive than from seed tubers because of the negligible storage and handling costs of the TPS. Potato production from TPS would therefore have the greatest potential in the developing countries. In developed countries, this production method would have some potential in commercial production as well as in home gardening. Research related to the TPS potato production has been mostly directed toward investigating suitable cultural practices, screening breeding lines for higher yield and warm climate adaptability, weed control in the field, and other similar production areas. Research concerning mechanization of TPS potato production has been limited. Engineering input to the TPS potato production, handling and storage needs considerable attention to develop practical and economical practices. This paper highlights some research areas which the authors believe are worth investigating. Engineering research that is conducted at the Coastal Plain Experiment Station related to the TPS potato production has been outlined along with future plans.     

A precision seeding device for true potato seed

A prototype apparatus was developed which can select and deliver single true potato seed to a specific location. The principle features of the unit include a system of vacuum and pressure nozzles connected to a rotating head to select and hold the individual seeds then eject them for planting. An airbrush was incorporated in the design to remove multiple seed from the nozzles. A small orifice and the radially oriented airbrush were fixed as a result of preliminary tests. Results of performance studies of the unit indicated that 84% single seed selection was possible. Parameters which influenced the performance of the unit were airflow rate from the airbrush and the level of vacuum in the manifold.     

Effect of supplemental nitrogen on true potato seed weight

The effect on true potato seed (TPS) weight of supplemental nitrogen (N) applied during seed development was investigated using crosses DTO-33 × R128.6 (“A” produced in the field) and Atzimba × R128.6 (“B” produced in the field and in a screenhouse). Dry weights of tops and tubers of the mother plants were also measured in the screenhouse. The response to supplemental N (0-240 kg/ha) in 100-TPS weight of cross A and B from the field was positive and linear. In the screenhouse, where higher total N (0-1200 kg/ha) was applied, the responses in 100-TPS weight and dry weight of tops and tubers were curvilinear, with maximum levels at 800, 1000 and 400 kg/ha, respectively. The 100-TPS weight of cross B was 40% higher in the field than in the screenhouse. In the field, increased frequency of supplemental N applications increased 100-TPS weight of large and medium berries of cross B, but had no effect on seed from small berries nor on seed from any berries of cross A. In the screenhouse, increased application frequency decreased tuber dry weight and increased dry weight of tops, but had no effect on 100-TPS weight. It was concluded that supplemental N must be applied during seed development and at higher total levels than those required for optimum tuber yields in order to maximize 100-TPS weight. The lower seed weight from the screenhouse suggests that other environmental factors (e.g., temperature) present during growth of the mother plant can affect the weight of the resultant TPS.     

An assessment of true potato seed families ofSolanum phureja

Summary Experiments were carried out withSolanum phureja germplasm which had been selected for tuberization response under W. European growing conditions. Selected clones and seedling (true potato seed; TPS) families ofS. phureja were raised in the field and tubers assessed for yield, tuber number, skin colour, size, shape and cooking characteristics. Some families had low within-family variances for cooked flesh hardness and some appeared as uniform for tuber size and shape as the selectedS. phureja clones. Skin colours of the tubers within TPS families were often assorted. The commercial potential ofS. phureja as a possible TPS-derived crop is discussed, as its self-incompatibility makes possible the cheap production of true potato seed.     

Techniques for successful field seeding of true potato seed

Crops of potatoes were successfully grown during each of 7 yrs from botanical seed planted directly into fields. During this period a total of 8 ha of direct-seeded potatoes was grown in 27 trials involving several soil types and several planting, cultural, and irrigation methods. Methods of seed production, extraction, treatment, and planting were developed along with methods of weed and insect control and methods of caring for growing seedlings so they would produce good yields of tubers, many of which were of commercial size and quality and very useful in a breeding program.     

Selection for improvement of potato populations grown from true seed

Field trials were conducted at Freeville, NY to determine if hybrid seedling populations ofSolanum tuberosum L. could be improved by two types of mass selection. Hill and bulk selections plus unselected controls were saved after harvesting tubers from transplanted seedlings of four Neo-Tuberosum × Tuberosum hybrids in 1982. Tubers from these three treatments were planted in a split plot design for comparison in 1983. Yields were increased 14 to 16% by hill selection; plants from this treatment were the largest and most vigorous. Uniformity of tuber shape and overall tuber appearance were improved by both hill and bulk selection.     

Detection of potato spindle tuber viroid in true potato seed by bioassay on Rutgers tomato

Various methods of preparing inoculum from single and composite samples of true potato (TP) seeds and TP seedlings were evaluated by bioassay on Rutgers tomato. An inhibitor of infection was found in concentrated plant sap prepared from composite TP seedlings that could be sequestered with RNasin or purified bentonite. Sap extracts from TP seedlings prepared in buffer containing bentonite were more infectious than nucleic acid extracts from an equivalent fresh weight of tissue. PSTV was detected in single seeds when sap preparations were inoculated on tomato and amplified to levels detectable by polyacrylamide gel electrophoresis.     

Selection against inbred seedlings in mixtures of inbred and hybrid true potato seed

Summary The effect of selection against weak plants was studied in artificial mixtures of hybrid (S₀), first self-pollinated generation (S₁), and second self-pollinated generation (S₂), true potato seed. Selection of vigorous seedlings in true seed populations raised in flats from mixtures of S₀ (25%), S₁ (50%), and S₂ (25%) seed increased the frequency of hybrids to 71%. In another study, two mixtures of S₀ and S₁ seed (1∶3 and 1∶1) were densely sown in beds to produce seedling tubers. Elimination of weak plants during population thinning and subsequent interplant competition significantly reduced the frequency of inbred plants. The resulting seedling tuber progenies were planted in the field and mean yields from the two mixtures of S₀ and S₁ seed were 96% and 99% of related completely hybrid progenies. The implications of these results for TPS production are discussed.     

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

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

Effects of plant density on the yield and yield components of true potato seed (TPS) hybrids in early and main crop potato production systems

This study was conducted to evaluate true potato seed (TPS) technology for use in ware or seed potato production in two contrasting environments in Turkey during 2002 and 2003. The field experiments were carried out in the Hatay and Nevsehir provinces in Turkey, which represent a Mediterranean early crop potato production area and a temperate main crop potato production area, respectively. The plug seedlings of six TPS hybrids were transplanted to the fields at four densities (15, 20, 25 or 30 plants m⁻²). The seed tubers of the medium early cultivar Marfona were also planted in the experimental plots to compare the performance of the TPS hybrids with traditional seed tubers. Transplanting of the seedlings was significantly delayed in Hatay due to unsuitable weather conditions in both years. The seedlings needed an adaptation period of 2–4 weeks after transplanting depending on the location and the growing conditions. The adaptation period was longer in Hatay due to high air temperatures after transplanting. Although the yield performance of the TPS hybrids differed depending on the location and year, the TPS hybrids produced noticeably higher total tuber yields in Nevsehir location (ranging from 43.1 to 62.5 t ha⁻¹ in 2002 and from 39.5 to 50.6 t ha⁻¹ in 2003) than in Hatay (ranging from 15.3 to 19.6 t ha⁻¹ in 2002 and from 15.1 to 19.1 t ha⁻¹ in 2003). The percentage of marketable tubers (>28 mm) was also considerably higher in Nevsehir. The optimal plant density varied between 25 and 30 plants m⁻² with regard to the total yield, while the optimal density with regard to the marketable yield was 20 or 25 plants m⁻² depending on hybrids in Nevsehir. However, none of the tested plant densities caused competition between plants in Hatay, where the environmental conditions during the growing period considerably restricted the growth of individual TPS seedlings.It was concluded that transplanting of TPS seedlings can be considered a feasible alternative for ware or seed potato production in temperate environments like Nevsehir that have growing periods of at least 4 months. However, there are several obstacles, such as difficulties with the timing of transplanting, long adaptation period that threaten the practicability of TPS technology in Mediterranean-type environments. Further agronomical studies focused on reducing inter- and intra-plant competition are needed for both environments in order to improve the acceptability of TPS technology to farmers.     

Tuber yields of families from open pollinated and hybrid true potato seed

This work was undertaken to compare the tuber yields, vegetative vigor and uniformity of seedling transplants obtained from different breeding methods. Twenty hybrid families from different groups of crosses involving 4x clones and 2x Phureja-haploid Tuberosum hybrids; 4x × 4x, 4x × 2x (FDR), 4x × (4x × 2x), and (4x × 2x) × (4x × 2x) and eleven open pollinated families from 4x clones, and 4x hybrids from 4x × 2x crosses were compared in a replicated yield trial. Families from 4x × 2x (FDR) crosses were the highest yielding among the hybrid groups having approximately twice the yield of the open pollinated 4x clones. They also were the best group in relation to plant vigor and uniformity. Based on these results, it appears that a good breeding scheme for high-yielding and uniform progeny from true potato seeds is the 4x × 2x hybridization method where the male parent is capable of producing 2n pollen via a first division restitution mechanism.     

Tuber yield of true potato seed families from different breeding schemes

Economical and environmental conditions in the south of Italy suggest that the direct utilization of TPS, as propagation material for potatoes, could be worth exploring. Thus, it is important to identify the most appropriate breeding scheme to enhance productivity and uniformity of the progeny. For this purpose 44 TPS families deriving from different breeding schemes and emphasizing different levels of heterozygosity were tested for yield at two locations in the U.S.A. and one in Italy. The results indicate the superiority of the 4x progeny from 4x X 2x crosses as a family group, and in the frequency of high yielding individual families in all locations. The 4x X 2x family group outyielded the OP progeny group by 45%, 79% and 114% at Hancock, Rhinelander (U.S.A.) and in Italy, respectively.     

General combining ability of Neo-Tuberosum for potato production from true seed

Neo-Tuberosum clones from the Cornell breeding population were evaluated as female parents in combination with Tuberosum for production from true seed. Field trials of hybrid seedling families were carried out in 1982 and 1983. Families were also grown in a hot greenhouse to measure combining abilities for tolerance to heat stress. General combining ability was highly significant for yield, vine and tuber characteristics, and heat tolerance. Several clones were identified which produced outstanding seedling families for yield, uniformity, and tuber appearance. Some individual crosses were equal to cultivars in yields, uniformity, and tuber appearance. Hybrids of Neo-Tuberosum and Tuberosum appear to be an excellent choice for potato production from true seed.     

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.