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.     

The effect of physiological age and planting date on the response of potatoes to applied nitrogen and on levels of residual nitrogen post-harvest

Summary Experiments were conducted on sandy and deep silty soils to assess the effect of physiological age of seed tubers and planting date on the response of potatoes to nitrogen fertiliser. Nitrogen optima commonly had large standard errors which made interpretation of the data difficult. On the sandy soil with cv. Record, early planting increased yield in two years but had no effect on mean N optimum (303 kg ha⁻¹, NOpt). Mean NOpt was less on the silty soil where the cv. Pentland Squire was grown, and was reduced from 273 kg ha⁻¹ to 241 kg ha⁻¹ when planting was delayed by 4 weeks. Physiological age had no effect on NOpt. On the sandy soil, residual soil mineral nitrogen (RSMN) increased by 0.05 kg ha⁻¹ per kg N fertiliser applied; on the silty soil the increase was four times as large. RSMN was larger following the late planted crop on the silty soil in one year.     

Beziehungen zwischen Stengel- und Knollenzahl bei der Kartoffel in Abhängigkeit von wichtigen Einflußfaktoren. I. Der Einfluß der Pflanzgutvorbehandlung und der Sorte

Zusammenfassung Die Pflanzgutvorbehandlung beeinflu?te die Stengelzahl signifikant. Abgekeimtes Pflanzgut der Sorten ‘Adretta’ und ‘Mariella’ entwickelte weniger Stengel und Knollen pro Pflanze jedoch mehr Knollen pro Stengel als vorgekeimtes und keimgestimmtes Pflanzgut. Die st?rker negativen Korrelationen zwischen Stengelzahl pro Pflanze und Knollenzahl pro Stengel sowie die h?here Reduktionsrate der angelegten Knollen bei der Sorte ‘Adretta’ weisen auf Sortenunterschiede in der Sch?rfe der Konkurrenz zwischen den Stengeln und innerhalb der Knollenanlagen eines Stengels hin. Die Ernteknollenzahl wurde bei ‘Mariella’ wesentlich durch die Zahl der Knollenanlagen, bei ‘Adretta’ hingegen st?rker durch die Reduktionsrate bestimmt.

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Summary Three different seed treatments and two cultivars were studied over seven years of field experiments (Table 1). Differences were detected between the cultivars in all characteristics studied: numbers of stems, maximum number of tubers (tuber initials), the number of harvestable tubers (>3 cm) at maturity per plant and per stem, and tuber reduction (percentage of initiated tubers that did not develop). Apart from the number of harvestable tubers, there were also differences between seed treatments (Tables 2, 3 and 4). Chitted seed of ‘Mariella’ and sprouted seed of ‘Adretta’ gave the greatest number of tubers per plant (Tables 3 and 4). In both cases desprouting reduced the numbers of stems and tubers per plant but increased the number of harvestable tubers per stem. Chitted seed set the most tubers per plant and per stem but had the highest levels of tuber reduction (Table 4). Due to intra- and inter-stem competition in both cultivars the percentage tuber reduction is significantly correlated with the number of tuber initials (maximum tuber number, Table 5). Smaller numbers of tubers per stem (Table 3) and significantly negative correlations between the number of stems and the maximum and harvestable number of tubers per stem (Table 5) highlight the effect of strong inter-stem competition in ‘Adretta’. Moreover, in this cultivar intra-stem competition seems to play an important role too. The rate of tuber reduction was significantly higher than in ‘Mariella’ (Table 3), and the final number of tubers significantly depended on the percentage of tuber reduction during the period of tuber growth (r=0,57^*, Table 5). In contrast, the number of harvestable tubers per plant in ‘Mariella’ was significantly correlated with the maximum tuber number during the period of tuber set (r=0,61^*, Table 5).

     

The potential for production of high quality seed potatoes in Tierra del Fuego Island, Argentina

Summary In Argentina, different areas are suitable for seed potato production: however, each has particular problems, mainly related to different pest and diseases. Tierra del Fuego Island is well isolated from traditional potato growing areas. Therefore, it was tested for its potential for seed production. The cultivars Achatt. Mailén INTA. Pampeana INTA and Spunta were grown in Río Grande, San Pablo and Ushuaia from 1991–1994. Nematode presence and aphid population dynamics were recorded. Average tuber yield ranged from 20.1–37.6 t ha⁻¹. After three years PVY and PLRV remained low (0–1% for different cultivars and locations). Moreover, seed tubers obtained were physiologically young. Long days, early frosts and strong winds may limit tuber yield in some years. The island can be considered as an ecological “safe haven” and is very suitable to obtain healthy and physiologically adequate seed potatoes.     

Effect of two plant growth regulators on the yield and quality of russet burbank potatoes

Summary Foliar applications of ethephon (ETH) 300 g a.i. ha⁻¹; chlormequat chloride (CCC) 920 g a.i. ha⁻¹, with a second application of 230 g a.i. ha⁻¹ approximately 2 weeks later; and a mixture of the two (ETH/CCC) 156 g a.i. ethephon and 299 g a.i. chlormequat chloride ha⁻¹ were made to field-grown Russet Burbank potatoes in 1986, 1987 and 1989. All the treatments increased the number of tubers set and reduced the average tuber weight compared to the control resulting in a reduction in premium and marketable tubers, and an increase in small tubers. Differences were greatest for ETH and least for CCC. ETH and ETH/CCC decreased the specific gravity, increased the incidence of deformities, and decreased the incidence of tubers with hollow heart. The growth regulators did not affect fry colour.     

Impact of Stolbur Phytoplasmas on Potato Tuber Texture and Sugar Content of Selected Potato Cultivars

Potato stolbur is a phytoplasmal disease that seriously affects yield and tuber quality in South Eastern Europe, Russia and the Mediterranean areas. In 2007 and 2008, field experiments were carried out to determine stolbur resistance of processing potato cultivars at Sannicolau Mare (Romania) by determining consistency and concentration of reducing sugars (fructose and glucose), sucrose and phytoplasmas in potato tubers. In both years, non-symptomatic potato tubers showed sucrose levels in the range of 3,000 mg kg⁻¹ fresh weight (FW). In contrast, sucrose concentrations were up to 11,820 mg kg⁻¹ FW in 2007 and 19,560 mg kg⁻¹ FW in 2008 in tubers showing severe symptoms. These high values severely affect suitability of tubers for processing as sucrose serves as substrate for the formation of reducing sugars that are the limiting factor in fried potato production for Maillard-related discolouration. The cultivars examined differed considerably in susceptibility to stolbur disease. Whereas cvs. ‘Courage’ and ‘Lady Rosetta’ showed high numbers of diseased tubers and high sucrose concentrations, ‘Lady Claire’ had a lower incidence of symptomatic tubers and lower sucrose concentrations. However, fully resistant cultivars were not observed. Across all cultivars examined, phytoplasmal concentration was significantly higher in symptomatic tubers than in non-symptomatic ones.     

The effect of seed-and soilborne inoculum ofColletotrichum coccodes on the incidence of black dot on potatoes

Summary Soil in a potato field naturally infested with black dot (Colletotrichum coccodes) was fumigated with methyl bromide at 126 g m⁻² or left unfumigated. Potato seed tubers (cv. BP1) uninfected, lightly infected (1–25% surface affected), severely infected (26–100% surface affected) and severely infected withC. coccodes but dusted with prochloraz manganese chloride as Octave 2.5% DP at 750 g per 100 kg seed were planted in fumigated and unfumigated soil. When harvested, the incidence of black dot on the progeny of infected seed planted in unfumigated soil was twice that of progeny in fumigated soil, with progeny of uninfected seed having a 68.5 times higher disease incidence in unfumigated soil. Black dot on progeny tubers was reduced by pre-treatment of seed with prochloraz in fumigated soil only. With black dot infested fields, planting disease-free seed or treating seed with fungicides would not decrease disease on progeny tubers.     

Performance of Dimethomorph + Mancozeb Applied to Seed Potatoes in Early Management of Late Blight (<Emphasis Type="Italic">Phytophthora infestans</Emphasis>)

Treating seed potatoes with contact fungicides prevents infection of Phytophthora infestans from tuber to tuber during handling but does not prevent field infections in the young plant. Dimethomorph (DMM) 9% + mancozeb 60% (Acrobat MZ, BASF) can cover both aspects due to the contact and systemic action of mancozeb and DMM, respectively. Experiments were performed under greenhouse and field conditions (three seasons and two locations) with cvs Kennebec, Shepody, Spunta, Russet Burbank, and Ranger Russet. Immediately after cutting, seed pieces were treated with Acrobat MZ at doses equivalent to 2, 3, and 4 kg ha⁻¹. At any dose, Acrobat MZ protected healthy seed tubers against P. infestans infections. Acrobat MZ (4 kg ha⁻¹) also protected the foliage of all cultivars against artificial inoculation of P. infestans, assessed by the detached-leaf method. These effects were observed up to 30 days after emergence in greenhouse experiments and up to 28 days after crop emergence under field conditions in two growing seasons. In cv Spunta, significant foliage protection was observed up to 35 days after field emergence whereas in seed tubers of cv Kennebec planted in sandy soils, significant foliage protection persisted longer. Additional evidence for acropetal translocation of Acrobat MZ in field crops was also found. With this strategy, there is no need to apply contact or systemic fungicides early in the season, and spraying costs and environmental risks are also reduced.     

Improving the field performance of micro-and minitubers

Summary In many seed potato producing areas, micro- and minitubers are too small for direct planting as seed tubers in the field. Such use of these propagules can, however, be feasible if the crop's growth and development can be advanced. Increasing light interception, harvest index and yield of useable progeny tubers has been proved possible with plastic mulch and pre-planting of small tubers in a greenhouse. High amounts of nitrogen (up to 180 kg ha⁻¹) or deep planting (up to 9 cm) were less effective. Using older or pre-sprouted micro- or minitubers may be beneficial, because this might increase the number of sprouts per mother tuber (and thus stems per plant) or advance the growth of sprouts or stems. However, this would require even more careful management, due to the weakness of these sprouts and stems. Micro- and minitubers should be as large as feasible when used for direct planting in the field.     

Treatment of seed potatoes with prochloraz for simultaneous control of silver scurf and black dot on progeny tubers

Summary Potato seed tubers infected withHelminthosporium solani andColletotrichum coccodes were treated with prochloraz (as Omega 450 g a.i. l⁻¹ EC) and/or prochloraz managanese chloride (as Octave 25 g/kg DP), and planted in two separate fields not previously cultivated with potatoes. Dipping seed 28 d prior to planting in 2,4 or 6 g a.i. l⁻¹ Omega, and dusting with 500 or 750 g Octave per 100 kg seed significantly reduced the incidence of silver scurf and black dot on progeny tubers. In one field, the higher concentrations of Omega and Octave gave slightly better control than the lower Omega concentrations. At the second site, postharvest application of 4 g a.i. l⁻¹ Omega or 750 g Octave per 100 kg seed limited development of both diseases on progeny tubers, with slightly better control when an additional Octave dusting was applied 14 d before planting. None of the prochloraz treatments adversely affected plant stand or tuber yield.     

Effect of planting date and inoculum level on incidence and severity of powdery scab on potato

Summary Powdery scab incidence and severity was examined on six potato cultivars planted at two different dates in a naturally infested field. There were two sub-plots; one where seed was exposed prior to planting to spores ofSpongospora subterranea from scabby peels, which were then added to the furrow at planting, and another where seed was exposed only to natural inoculum within the field. The later planting data reduced incidence and severity, but there were no differences between sub-plots. All cultivars became infected, but ‘Rosa’ was the most susceptible and ‘Katahdin’ the most resistant. Contribution No. 1720, Department of Plant Pathology, The Pennsylvania Agricultural Experiment Station. Authorized for publication September 22, 1988 as Journal Series Paper No. 8007.     

Prevention of berry formation in potato plants (Solanum tuberosum L.) by single foliar applications of herbicides or growth regulators

Summary Thre seed production in potato plants (Solanum tuberosum L.) may contribute to the persistence of potato cyst nematodes and of viruses, fungi and bacteria. In four experiments MCPA, ethephon, 2,4D-amine, naphtylacetamide, metoxuron and gibberellic acid were tested for their potential to reduce berry formation. MCPA (500 or 750 g a.i. ha⁻¹ and ethephon (144 or 192 g a.i. ha⁻¹) reduced or almost completely prevented berry set and their effect was strongly influenced by the crop growth stage at the time of application. For both chemicals application at early bud stage was the most effective and, whereas MCPA showed no adverse effects on tuber yield, size, dry matter content and fry colour, ethephon substantially reduced the percentage of large tubers over 50 mm.     

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.     

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.     

Beziehungen zwischen Stengel- und Knollenzahl bei Kartoffeln in Abhängigkeit von Wachstumsregulatoren

Zusammenfassung In dreij?hrigen Feldversuchen führte eine Behandlung der Pflanzknollen mit vier Wachstumsregulatoren zu einer signifikanten Erh?hung der Stengel- und Knollenzahl pro Pflanze sowie einer Verminderung der Knollenzahl pro Stengel. Die durch die Behandlung erzielte signifikante Erh?hung des Pflanzgutertrages war jahres- und sortenabh?ngig. Eine hohe Effektivit?t der Behandlung ist nur zu erwarten, wenn die Erh?hung der Stengelzahl nicht zu einer sorten- oder jahresbedingten starken Verminderung der Knollenzahl pro Stengel führt.

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Summary Growth regulators (K350, GA₃, Azoluron and thiourea) were applied in a three-year field experiment to tubers of four large-tubered cultivars of different maturities (‘Arkula’, ‘Auralia’, ‘Dorisa’ and ‘Libana’). They produced significant increases in the numbers of stems and tubers per plant and a decrease in the number of tubers per stem. Only the most effective preparations increased the yield of seed and decreased overall yield, averaged over cultivar and year. Positive correlations between numbers of stems and tubers per plant contrasted with the negative correlation between the number of stems and number of tubers per stem (Fig. 1). The preparations ranked in effectiveness as follows: K350>GA₃>thiourea>Azoluron, and this was reflected in the number of stems and tubers per plant (Table 2). Increases in number of stems resulting from treatment with the regulators effectively increased the yield of seed, but only if the increases were not accompanied by strong year or cultivar related reductions in the number of tubers per stem caused by inter-stem competition (Tables 3 and 4).

     

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.     

The effect of irrigation and nitrogen on powdery scab and yield of potatoes

Summary Powdery scab, caused by the fungusSpongospora subterranea, has developed in the Cappodocia region of Turkey because of changes in agronomic practices, such as excessive irrigation and nitrogen fertilizer use and growth of highly susceptible cultivars. The most suitable irrigation and nitrogen application levels were established to maintain powdery scab at minimum levels without affecting potato yield. Three irrigation levels were used in 1998 (673, 897, 1121 mm) and five in 1999 (329, 494, 658, 823, 987 mm). Nitrogen levels were applied 150, 300, 450, 600 kg N ha⁻¹. In 1998, least powdery scab occurred with 673 mm irrigation, which yielded 41 t ha⁻¹ potatoes. The lowest disease severity occurred in 1999 with 494 mm irrigation and 150 kg N ha⁻¹. At these levels, tuber yield was 34 t ha⁻¹ which was not significantly different from the highest yield measured. In 1999 and at two of the three irrigation levels inl998, nitrogen increased disease severity.     

Microtuberization of Potato (Solanum tuberosum L.) as Influenced by Supplementary Nutrients, Plant Growth Regulators, and In Vitro Culture Conditions

Five experiments with in vitro-grown plantlets of potato cvs ‘Superior,’ ‘Early Valley,’ ‘Golden Valley,’ and ‘Winter Valley’ were carried out to investigate in a stepwise approach the potential for enhancing microtuber production of (1) adding supplementary nutrients (SN) including KNO₃, NH₄H₂PO₄, Ca(NO₃)₂.4H₂O, and MgSO₄ in full- or half-strength Murashige and Skoog (MS) medium, (2) adding a pretested combination of plant growth regulators (PGRs), i.e., 10 mg l⁻¹ 6-benzyl aminopurine plus 200 mg l⁻¹ succinic acid 2,2-dimethylhydrazide, (3) varying the timing of the supplemental applications, and (4) varying the replenishment of the medium. Plantlets of ‘Superior’ for microtuberization were grown from two-node explants for 75 days under environmental conditions consisting of 22 ± 2 °C and a 16-h photoperiod on a solid basal medium consisting of half-strength MS (1/2 MS) medium containing 6 % sucrose and a moderate concentration of supplementary nutrients, SN-2 (KNO₃, 1.22 g l⁻¹; NH₄H₂PO₄, 1.41 g l⁻¹; Ca(NO₃)₂4H₂O, 0.23 g l⁻¹; and MgSO₄, 0.74 g l⁻¹). Thereafter, plantlets were grown for 60 days under dark conditions. Liquid media containing different combinations of MS, SN, and PGR levels plus 8 % sucrose were added as a supplement and were evaluated for their ability to increase tuberization compared to the control composition of the supplement (MS with 8 % sucrose). In the first experiment, addition of 1/2 MS liquid medium containing 8 % sucrose and SN-2 before dark incubation induced the highest total number of microtubers (on average 1.4 per plantlet), a significantly higher weight and size than the control, and the highest percentage (50 %) of large-sized (>500 mg) microtubers. In the second experiment, addition of 1/2 MS liquid medium containing 8 % sucrose, SN-2, and PGRs produced the highest number (on average 1.5 per plantlet) and total yield (on average 971 mg per plantlet) of microtubers, and significantly the highest percentage (66 %) of large-sized (>500 mg) microtubers. The size of the microtubers was higher than for the treatment without growth regulators. The optimum time for addition of supplemental medium containing 8 % sucrose, SN-2, and PGRs was shown in experiment 3 to be latest 1 week before dark incubation. This timing resulted in both the highest microtuber number (on average 1.6 per plantlet) and yield (on average 1208 mg per plantlet), and the highest percentage (64 %) of large-sized microtubers. Finally, it was found that a second supplemental treatment consisting of 50 % replacement of the liquid medium (by volume) 2 weeks after transfer to dark conditions gave rise to the highest number (on average 1.9 per plantlet), yield (on average 1346 mg per plant), and also significantly the highest percentage (25 %) of large-sized microtubers (>1000 mg) as compared to replacement of a greater or smaller proportion of the medium. Four potato cultivars, ‘Superior,’ ‘Early Valley,’ ‘Golden Valley,’ and ‘Winter Valley’ produced acceptable numbers and yield of microtubers of relatively large-sized tubers using a process that included supplemental liquid medium with 1/2 MS, 8 % sucrose, moderate concentration (SN-2) of SNs and PGRs, followed by a 50 % replacement of the same medium.     

Field performance of potato microtubers as propagation material

Summary In five field trials with the cultivars Gloria (early), Bintje (mid-early) Désirée (mid-late) and Morene (late), crops grown from conventional 28–35 or 35–45 mm seed were compared with crops grown from microtubers, of various sizes and from various sources, that had been producedin vitro. The following means to quicken initial crop development from the micropropagated material were tested: large microtubers, plastic soil cover, and transplanting of plantlets grown from microtubers pre-planted in a glasshouse. Crops grown from microtubers weighing less than half a gram yielded much less than crops grown from conventional seed crops but their yields were increased by each treatment. With the later-maturing cultivars, which generally produce few tubers per plant, the yields within seed grades from plants grown from transplanted microtuber plants were comparable with those of conventional crops. Reasons are given, why direct planting of microtubers, with or without plastic foil, is not a practical option.     

Potato production from true potato seed (TPS) in Egypt: Effect of the growing season on seedling development,recovery from transplanting and yield

Summary Ware potatoes were produced from true potato seed by transplanting seedlings to the field in different growing periods to evaluate environmental constraints of this production method in the Nile delta. In the autumn season, with high temperatures and long-day conditions during seedling culture in the nursery and transplant establishment in the field, seedling development was fast, and transplants resumed growth within 5 days of transplanting in the field. Tuber yields ranged between 120 and 160 dt ha⁻¹. In the spring season, with low temperatures and short-day conditions during the initial growing phase, seedling development in the nursery was slow and biomass partitioning between above ground organs (stems, leaves) and tubers was shifted towards the tubers. This partitioning was further enhanced by transplanting the seedlings in the field. Seedlings recovered only slowly from transplanting or died. It is concluded that potato production via transplants is poor in the spring season when premature tuberization of seedlings in the nursery leads to slow field establishment and low tuber yield.