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.     

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

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

Ion chromatography analysis of phosphite uptake and translocation by potato plants: Dose-dependent uptake and inhibition of Phytophthora infestans development

Phosphite-based fungicides are increasingly used to control fungi-like plant pathogens from the Oomycetes group. A rapid, precise, and cost-effective suppressed conductivity high performance ion chromatography (HPIC) method was developed to assess the concentrations of soluble phosphites (Phi) and phosphates (Pi) in plant samples. This technique was used to determine the amount of Phi and Pi in leaves and tubers of potato plants following foliar applications of the Phi-based fungicide Confine™. High amounts of Phi were determined in both leaves and tubers indicating that potato plants efficiently uptake and translocate the fungicide. The number of applications of Confine™ and its concentration were found to be directly proportional with the amount of Phi detected in potato plants and inversely proportional with the development of Phytophthora infestans (Mont.) de Bary in these plants. Levels of Phi comparable to those determined in plants were found to strongly inhibit the growth of P. infestans in vitro. The simultaneous estimation of the in planta Phi concentration and of the sensitivity of P. infestans to Phi represent the most comprehensive approach of assessing the efficacy of Phi-based fungicides in controlling late blight development in potatoes.     

Seed tuber production from true potato seed (TPS) in Egypt and the influence of environmental conditions in different growing periods

Summary The effect of environmental conditions on seed tuber production from true potato seed (TPS) in nurseries was evaluated in different growing periods during two seasons in Egypt. In the autumn season, high soil and air temperatures reduced emergence and initial foliage development of early-sown seedlings, and decreased tuber yields. In late-sown seedlings low night temperatures and short daylengths caused early tuberization, poor foliage development and low tuber yields. In the spring season, low temperatures and short daylengths resulted in a slow initial foliage development and early haulm-tuber competition for assimilates in early-sown seedlings. However, tuber yields were higher than for late-sown seedlings, presumably because net assimilation and assimilate partitioning to the tubers were impaired by above optimum air and soil temperatures in May and June. Slow development of true seed-sown plants caused a high sensitivity towards adverse environmental conditions and would limit yielding ability in Egypt.     

不同营养方式对雾培法生产脱毒种薯的影响

叶面营养在马铃薯种薯生产过程中有着十分重要的作用,但是在种薯生产上只喷叶面营养液的研究还鲜有报道。为了充分了解叶面营养对种薯生产的影响,本试验采用二因素随机区组试验设计,研究3种不同营养方式对雾培法生产脱毒种薯效果的影响。结果表明,这3种营养方式在前期对马铃薯生长影响较小,但块茎形成后,采用叶面营养与根系营养相结合能显著提高马铃薯种薯产量,只喷叶面营养也能形成马铃薯,但是数量很少。这说明叶片对营养的吸收效率较根系高,但是有一定量的限度,这种作用在块茎形成后表现的尤为明显。     

Determining the feasibility of measuring genotypic differences in skin-Set

Replicated experiments with various potato cultivars having diverse tuber skin types demonstrated that the Halderson periderm shear tester was sufficiently sensitive to measure genotypic and phenotypic differences in skin-set (periderm maturity). All genotypes had lower skin-set readings at the bud end of the tuber compared to the equatorial region and stem end. The technique employed with the shear tester objectively resolved genotypic differences in the developmental time courses for skin-set and clearly showed that the periderm of Russet Burbank tubers matured more rapidly than the periderm of other cultivars with smooth skin types. However, a consistent relationship between periderm weight and skin-set could not be established. In postharvest experiments designed to describe the phenotypic effect of temperature and relative humidity on tuber periderm maturation, we found that high relative humidity retarded the development of skin-set. The ability to detect genotypic and phenotypic differences with this technique for measuring skin-set indicates that it is feasible to further develop a standardized procedure suitable for testing diverse skin types in breeding and certified seed programs as well as for use by growers of table stock, seed, and chipping potatoes.     

整薯播种对马铃薯生育及产量的影响

1979～1984年,在黑龙江省北部黑土地区气象条件、生产水平和栽培条件下,通过田间试验,研究了整薯播种对马铃薯生育和产量的影响。结果表明:整薯播种与传统习惯的切块播种相比,6年期间平产出现频率为2次,一般年份整薯播种比切块播种增产9～12%,在春旱严重的1980年,整薯播种表现出非常突出的抗旱保苗效果。在群体叶面积发展进程上,整薯播种表现早发早衰,切块播种晚发晚表,一般年份光合势前者比后者高9.6%,春旱严重的1980年高82.8%。块茎商品率以112.5克为准时,6年平均整薯播种为74.1%,切块播种为80.0%,两者相差5.9%;以50克为准时,整薯播种为97.3%,切块播种为98.2%,两者相差0.9%。     

Relationship of potato tuber periderm resistance to plant water status

Potato (Solanum tuberosum L. cv. Russet Burbank) tuber periderm resistance to water loss was monitored during the harvest season. Periderm resistance of tubers from water-stressed plants was compared with tubers from unstressed plants throughout a six-week harvest period, in order to determine the effect of plant condition on tuber resistance to water loss. Tubers stored for ten days at 4°C immediately following harvest were also monitored to determine if storage enhanced periderm resistance and if any difference occurred between tubers from stressed vines compared with those from unstressed vines. During the harvest season, tuber resistance to water loss was positively correlated with plant water stress, as measured by leaf water potential and leaf diffusive resistance. Storage of tubers after harvest also caused an increase in periderm resistance. The commercial practice of vine killing, therefore, may have a positive effect on reducing weight loss in storage by enhancing the resistance of tuber periderm to water loss.     

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

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

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.     

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.     

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.     

Investigations into the mode of resistance of potato tubers toFusarium roseum ‘Sambucinum’

In a histological study comparing tuber resistance of potato clone B7200-33 and susceptible variety “Russet Burbank” toFusarium roseum ‘Sambucinum’, the formation of suberin and wound periderm was found to be an important resistance mechanism. In B7200-33 tubers a continuous suberin layer was formed whereas in ‘Russet Burbank’ tubers the suberin was formed in clumps so that the pathogen easily could invade the tissue between the clumps but not through a continuous layer. Wound periderm also was formed at a more rapid rate in B7200-33 than in ‘Russet Burbank’ tubers thereby “walling off” the pathogen and reducing decay.     

马铃薯二年制脱毒种薯体系建设及其关键技术改良

马铃薯脱毒种薯生产和利用是马铃薯生产的重要环节,传统的脱毒种薯生产体系因繁殖周期长,病毒再侵染风险高,使种薯质量很难保证。本研究以品种脱毒和试管薯生产为基础,以微型薯生产和标准种薯生产为扩繁环节,建成了二年制种薯生产体系。该体系将种薯生产在田间多年繁殖改进为只需一年繁殖,从而降低了病毒再侵染机率,保证了脱毒种薯质量。     

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.     

Relationship between resistance to late blight in potato foliage and tubers of cultivars and breeding selections with different resistance levels

Due to changes in the pathogen population, late blight of potatoes caused byPhytophthora infestans has become a more difficult disease to manage and there is a need for new potato cultivars with greater and more stable disease resistance. Field studies are required to identify and characterize host resistance to late blight in both foliage and tubers but, as epidemics vary from year to year, combining multi-year results can be difficult. Residual maximum likelihood (REML) was successfully used to analyze data which demonstrated good correlations between foliar and tuber responses to late blight (US-1 genotype). In addition, studies on post-harvest inoculated tubers provided more reliable disease responses than field studies, and the disease resistance with this method correlated well with foliar disease responses. This tuber test would be a useful method of pre-screening selections for disease response prior to testing in the field.     

Influence of mefluidide on tuber development,maturity, and storage of Russet Burbank and Norland potatoes

Mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl] amino] phenyl] -acetamide}, a chemical with plant growth regulator properties, was applied to the foliage of potatoes (Solanum tuberosum L.) in field experiments to determine its effects on tuber development, maturity, and storage of the cultivars Russet Burbank and Norland. The rate of sucrose loss before harvest was reduced in mefluidide-treated plants. Total and marketable yields generally were lower in treated plants. Specific gravity tended to increase in Russet Burbank with application rates up to 1.0 kg ai/ha mefluidide. Preharvest treatments of mefluidide resulted in an increase in periderm thickness and russeting. However, weight loss during storage was greater in tubers from treated plants. Less sprouting occurred in storage in tubers from mefluidide-treated plants. Mefluidide resulted in a lower anthocyanin content and consequently an undesirable color change in Norland tubers.     

Effects of Foliar and Tuber Sprout Suppressants on Storage of Ware Potatoes under Tropical Conditions

Potato (Solanum tuberosum L.) is an important source of dietary carbohydrate and cash income generation for farmers in the tropical highlands of Kenya. The feasibility for cold storage at the farm level is limited due to the high costs of maintaining such a facility and there is limited data on the long-term post-harvest storage and quality of tubers of tropical-adapted cultivars. Application of sprout suppressants to control premature sprouting of ware potato is an attractive proposition. The objectives of this study were to evaluate the efficacy of pre-harvest foliar applications of paclobutrazol (PBZ) and ethephon for sprout suppression on ware potato tubers in storage. Post-harvest spray applications of Isopropyl N-(3-chlorophenyl carbamate) chloropropham (CIPC) and 1,4-dimethylnaphthalene (DMN) on tubers as fog was also evaluated. Potato cultivars had varying levels of tuber dormancy. The tubers were stored at ambient temperature (23 C) and evaluated weekly for 24 weeks for percent of tubers sprouting, length of longest sprouts, tuber weight loss and assessed for dormancy for 24 weeks. Paclobutrazol prolonged tuber dormancy by 21–31 days and reduced tuber weight loss. Ethephon treatment had no effect on dormancy and tuber weight loss. Potato tubers treated with CIPC had greater sprout control than the other treatments in storage. Tuber response to DMN treatment varied among the three potato cultivars evaluated. The findings from this study imply that PBZ is effective in prolonging potato tuber dormancy for short-term basis at 23 C, while CIPC applied on tubers was effective for long term storage. Optimization of post-harvest potato storage can improve food security in the highland tropics.     

Comparison of periderm color and anthocyanins of four red potato varieties

The color, anthocyanin content per given surface area, and phenolics content of tuber periderm of four different varieties of red potatoes were compared. Three of the varieties, Norland, Red Norland, and Dark Red Norland, are members of a color sport family. Freshly harvested ‘Norland’ differed significantly in color, but not anthocyanin content per given surface area, from its sports. ‘Red Norland’ tubers were lighter in color than those of ‘Dark Red Norland’. In general, storage resulted in darkening of tubers and, except for the fourth variety, MN17922, a decrease in anthocyanin content per given surface area. Tubers from green-killed ‘Red Norland’ plants were more purplish-red than those from vine-killed plants. Stored tubers had greater periderm total phenolics content than freshly harvested tubers. The increase in periderm phenolics and decrease in anthocyanin content per given surface area may lead to darkening of tubers with storage. Cell walls connecting periderm to cortex tissue of ‘MN17922’ tubers were thinner than those in ‘Norland’ tubers, which may explain why it is realtively easy to separate the periderm of ‘MN17922’ from its cortex.     

Effect of production temperature of seed potatoes on subsequent yielding potential

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