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.     

Effect of second growth on the quality of tubers as seed in the cultivar Record

Summary Seed quality in a crop harvested in 1984 was compared in tubers which either, (a) were unsprouted prior to harvest (normal), (b) had formed secondary chain tubers prior to harvest (primary), (c) secondary chain tubers. Normal and primary tubers formed substantial sprout growth during storage, while there was little sprout growth from secondary tubers. Plants derived from these seed tuber types differed, in terms of emergence, number of emerged stems, and tuber number. It is concluded that the tuber types can be considered to vary in terms of physiological age; normal and primary tubers appear to be physiologically older than the secondary tubers. This variability in seed condition can lead to variability in the performance of the subsequent crop.     

Fungicide treatment of seed tubers infected with thiabendazole-resistantHelminthosporium solani andPolyscytalum pustulans for controlling silver scurf and skin spot on stored progeny tubers

Summary Seed tubers, cv. Désirée, derived from stocks treated annually with thiabendazole were infected with thiabendazole-resistant strains ofHelminthosporium solani andPolyscytalum pustulans. Samples of seed tubers were either untreated or immersed for 5 min in fungicide suspensions of thiabendazole, imazalil or thiabendazole plus imazalil and planted on four farms in 1988 and 1989. After harvest, tuber samples from each treatment were treated with thiabendazole and stored for 6 months. Applying imazalil or thiabendazole plus imazalil to seed tubers decreased the severity of silver scurf and skin spot on stored progeny tubers. Thiabendazole applied to seed tubers or to progeny tubers after harvest did not affect the severity of either disease, but post-harvest treatment decreased the incidence of black scurf after storage.     

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.     

Comparative effects of cut and treated seed tubers vs untreated whole seed tubers on seed decay, Rhizoctonia stem canker, growth, and yield of Russet Burbank Potatoes

Whole seed tubers have been reported to have performance advantages over seed tubers that have been cut, even if the cut tuber pieces are treated with a fungicide dust. For this study, whole seed tubers were compared to cut seedpieces and to cut seedpieces treated with four different commercial fungicide dusts for five consecutive seasons. A new field generation 3 Russet Burbank seed lot was used for each of the five years of this study. Both whole tubers and cut seedpieces were inoculated withFusarium spp., and the seedpieces were then treated with a fungicide dust. Inoculated and uninoculated untreated controls were also included. Emergence,Fusarium seed decay,Rhizoctonia stem canker, stem numbers, and vigor, as well as yield and grade data were obtained.Rhizoctonia stem canker in stems grown from whole seed tubers was significantly higher than in stems from seedpieces receiving fungicide treatment in several of the study years. Predicting whole seed tuber performance is difficult because performance varies more from year to year than performance of cut and treated seedpieces. Yield performance of whole seed tubers was not significantly better than cut and fungicide-treated seedpieces in any experimental year, and yield of large (over 280 g) tubers was significantly less than that recorded for two of the treatments when data from all five years were combined. This study demonstrated that untreated whole seed did not outperform cut and treated seedpieces for vigor, stem numbers, disease ratings, or yield in small plot comparisons for five consecutive seasons.     

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.     

Controlling parasitic nematodes and soil-borne diseases of potatoes with soil fumigation

The fumigation of soil infested with a moderate population of parasitic nematodes and fungi very effectively improved the growth, quality and yield of potatoes. The beneficial effects of fumigation with DD and Vorlex were mainly attributed to control of nematodes, particularly the meadow nematode. However, the fumigants did effectively reduce the population ofRhizoctonia solani on potato roots and “scurf” on tubers caused byR. solani. Also less vascular browning of tubers developed in fumigated soil. Thus the effects of soil fumigation were complex, affecting many microorganisms and consequently producing numerous manifestations in the growth of potatoes.     

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.     

Effects of wounding fungicide-treated potato seed tubers on silver scurf disease on daughter tubers at harvest

Summary Silver scurf on daughter tubers at harvest was decreased by treating seed tubers with imazalil or thiabendazole in March but significantly increased when the treated tubers were wounded the day before planting in May. The disease was also increased by wounding seed tubers not treated with fungicide. Black dot was decreased by seed treatment with imazalil but was not affected by wounding.     

The effect of water stress on the yielding capacity of potato crops and subsequent performance of seed tubers

Summary The effect of water stress on yielding capacity of potatoes was studied in 3 years using four different levels of soil water potential (0.7, 1.9, 3.4 and 7.8 atm.) in experiments in specially adapted structures that excluded uncontrolled water supply. Seed tubers from these crops were planted in the following years to investigate effects of water stress on their subsequent performance. Limited soil moisture availability decreased yield and the number and size of tubers. The growing period was shortened by 1–4 weeks and dormancy period by 2–8 weeks. In the following year, seed produced under conditions of moisture stress gave plants with 20% fewer stems. 24–33% less yield, 18–22% fewer tubers and 19–22% fewer large tubers than plants from seed produced under abundant water supply. It is concluded that the yield potential of seed tubers can be improved by careful attention to the availability of soil moisture during their production.     

Advancing growth vigor of seed potatoes by a haulm application of gibberellic acid and storage temperature regimes

Seed tubers that are planted soon after their harvest give low yields because of dormancy and low growth vigor. In the research reported in this paper, we investigated the advancing effect of a haulm application of gibberellic acid (750 g GA/ha) 6 days before haulm pulling and its interaction with storage temperature regimes on the growth vigor of immaturely harvested seed tubers of three cultivars. The effects on tuber yield were also examined in one experiment. The storage regimes were: 18 C continuously, hot pre-treatments of different duration (different periods at 28 C and subsequently 18 C) and a cold pre-treatment (20 days at 2 C and subsequently 18 C). Both a foliar spray with GA and storage at 28 C enhanced physiological aging of the tubers and greatly advanced the growth vigor, without negative effects on the morphology of the plants. There was a clear interaction between the GA treatment and the storage temperature regime. At early planting, the effect of the treatments on tuber yield were small for Diamant (short dormancy), but strongly positive for Désirée and Draga (long dormancy).     

Tillage and seed-sprouting strategies to improve potato yield and quality in short season climates

Management practices that accelerate crop development and allow earlier harvest would be beneficial in short-season potato (Solanum tuberosum L.) production areas. Yield and quality of the potato cultivar ‘Russet Burbank’ were evaluated in a 2-yr study in northern Maine to determine effects of soil tillage and seedsprouting treatments designed to dry soil early in the spring and hasten seed emergence. The tillage treatments, consisting of fall raised bed (RB), fall ridge till (RT), and spring chisel plow (CH), were tested in combination with green-sprouted and non-sprouted seed tubers on a Caribou gravelly loam (coarse-loamy, mixed, frigid,Typic Haplorthod). Plants from green-sprouted seed emerged earlier than from non-sprouted seed tubers (87%-96% vs 21%-37%, respectively, at 18 days after planting [DAP] in 2000; and 73%-88% vs 18%-23%, respectively, at 20 DAP in 2001). Green-sprouted seed tubers in RB yielded 4.6 to 5.9 T ha^-1 more than nonsprouted seed tubers in RB. However, non-sprouted seed tubers yielded higher than green-sprouted seed tubers in RT by 2.9 to 4.2 T ha^-1 and in CH by 1.1 to 4.1 T ha^-1. Similarly, green-sprouted seed tubers in RB and nonsprouted seed tubers in RT and CH produced higher marketable yield, greater tuber length, and greater tuber diameter than the corresponding seed-sprouting treatment. In the comparatively wetter year (2000), the use of green-sprouted seed tubers in RB significantly increased total and marketable yields, and produced longer and larger tubers than all other treatments. However, in 2001 (relatively dry year), yield and quality from green-sprouted seed tubers in RB did not differ from non-sprouted seed in RT or CH. Green-sprouted seed produced fewer sunburned and rotten tubers, but more misshapen tubers than non-sprouted seed in RB tillage. The technique of producing Russet Burbank potatoes in raised beds is a promising system in regions with short growing seasons for enhancing early soil drainage during spring and improving soil water retention during critical periods of crop growth and development.     

Impact of Seed Cutting and Seed-Borne Inoculum on Daughter Tuber Common Scab and Plant Growth

Common scab (CS), caused primarily by the filamentous, soilborne bacterium Streptomyces scabies, creates significant challenges in the production of quality potato tubers in global growing regions. Over the past several decades, numerous studies been conducted to improve our understanding of the impact of cultural and pesticide treatments for managing the health of progeny daughter tubers. None of the previous studies, however, have addressed differences between the impacts of CS from whole seed vs. cut seed pieces on resulting disease on daughter tubers. A greenhouse trial was conducted during 2013–2014 to assess the impact of seed type and CS severity on plant health and CS on daughter tubers. Cut and suberized ‘Snowden’ seed pieces (~2 oz.) exhibiting 0, 5, and ≥50% CS severity were sown in 3-gal pots containing a 50:50 mix of sterilized sand and field soil. Whole ‘Snowden’ seed tubers (~2 oz.) with the same three levels of CS severity were sown under the same conditions. At harvest, approximately 20% of daughter tubers from asymptomatic seed pieces (both cut and whole) exhibited symptoms of CS. Disease incidence and severity significantly increased for pieces that had 5 and ≥50% CS across both experiments. Plants grown from whole seed had significantly higher yield, on average, when compared to cut seed. Daughter tubers produced from whole seed resulted in higher CS incidence than those from cut seed in one of our two experimental trials. Our results indicated a clear advantage to plant common scab-free seed potatoes with the aim of producing healthier daughter tubers.     

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.     

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.     

Seed yield,oil content and fatty acid composition of Oenothera biennis L. affected by harvest date and harvest method

Evening primrose (Oenothera biennis L.) has become a subject of agricultural interest because of the potential market for γ-linolenic acid, which is useful in medicine and nutrition. O. biennis has good potential for agricultural production, but due to its indeterminate growth it can not be harvested at once as seed are formed and ripened heterogeneously. As a result there is high seed wastage due to shattering. Field experiments were carried out to verify the influence of the harvest time (early, middle and late) and harvest method (conventional harvest method, defoliation by herbicide and defoliation by flame) on the seed yield, seed yield components, oil content, fatty acid composition and protein content of the O. biennis L. cv. “Anothera”. From the results of the three harvest times in the autumn-sown experiment, a significant influence on seed yield was observed in the late harvest. Of all the three harvest times in the spring experiments, not showed any significant influence on seed yield. However, the harvest method did produce a significant influence on seed yield in the first spring experiment. Different harvest times did not have significant influence on oil content except the second spring trial. The harvest method led to significant differences on the oil content when the plants were sown in autumn. In the second spring experiment seed protein content was significantly influenced by harvest time. In all experiments, the content of γ-linolenic acid (GLA) was influenced by harvest time. Based on obtained results, it can be concluded that 75–80 and 100 days after flowering could be recommended as harvest times for spring and autumn-sown O. biennis L. cv. “Anothera” in Germany, respectively. Desiccation as a harvest technique in some cases tended to influence on seed yield, PDM, SDM, oil content, stearic acid, oleic acid and linoleic acid. Defoliation by herbicide was more effective than those of flame in our experiments.     

赤霉素打破种薯休眠对马铃薯生长及产量的影响

实验结果表明:用50mg/L赤霉素浸泡小整薯1h不但可以有效的打破休眠,同时还可以增加有效茎数,提高单株叶面积,从而使单株结薯数和产量增加。     

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

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

Analysis of growth and yield of maize,sunflower and soybean grown at Balcarce,Argentina

The objectives of this study are: (1) to analyze the capacity of maize, sunflower and soybean to produce dry matter and seed yield, including the responses to shading during flowering, and shading and thinning during seed filling; and (2) to evaluate effects of plant density and sowing date on growth and yield. This report integrates data obtained during seven years of research at Balcarce Experimental Station, Argentina. In these experiments, nutrients and water were not limiting to growth. Maize produced the most biomass because of sustained ground cover and high light conversion efficiency. It also had the largest harvest index on a dry weight basis. When dry matter was expressed in glucose equivalents, differences among harvest indices for the three crops were smaller. Flowering in maize, seed filling in soybean and flowering and seed filling in sunflower were critical periods in determination of grain yield. Sunflower had more capacity than maize to compensate for fewer grains through greater grain weight. Maize and sunflower had low stability in grain number at less than optimal plant densities. Finally, delays in sowing date significantly reduced grain yields of the three crops. These reductions were due to decreases in number of grains per m² and in grain weight.     

Effect of seed tuber and seed piece size on growth and incidence of hollow heart in Norgold Russet potatoes

Small seed pieces decreased yield and number of tubers. Both seed tuber and seed piece size affected the percentage of tubers with hollow heart. Hollow heart increased from 14 to 22% as the seed tuber size increased from 57 to 228 g and decreased from 27 to 19% as the seed piece size increased from 28 to 57 g. The least hollow heart (11%) occurred in tubers of plants grown from 57 g whole seed pieces and the most (26%) in tubers of plants grown from 228 g seed tubers cut into 28 g seed pieces. Hollow heart was positively correlated with the mean tuber size and negatively correlated with the number of mainstems per hill, total yield, and total number of tubers.