The effect of harvest time on the accumulation of reducing sugars during storage of potato (Solanum tuberosum L.) tubers: Experimental data described, using a physiological based, mathematical model

Summary The physiological based mathematical model describing the storage behaviour of potato (Solanum tuberosum) tubers was examined to determine its ability to explain the changing storage behaviour as a function of harvest time for ten different cultivars. Between 90 to 98% of the observed variance was accounted for. This confirmed the models concept that the maturity at time of harvest determines the storage behaviour through the initial amount of the enzyme (or enzyme system) responsible for cold induced sweetening.     

Long-term responses in the yield of Eastern Gamagrass [Tripsacum dactyloides (L.) L.] to nitrogen fertilizer under two harvest regimes in the United States

Eastern Gamagrass [ Tripsacum dactyloides (L.) L.] is a perennial C₄ grass with potentially high productivity. Intensive management through the application of nitrogen (N) fertilizer and frequency of cutting, however, may be required to maximize its potential for forage production. This study determined the long-term and residual responses of Eastern Gamagrass in terms of dry matter (DM) yield and tiller density to three annual application rates (0, 50 or 100 kg ha⁻¹) of a N-fertilizer solution applied by broadcasting or knife placement for 5 out of the 10 years of the study, and harvested using one-cut or two-cut regimes. Application of N-fertilizer increased total DM yield in the 5 years of N applications by 0·44 with the first increment of 50 kg N ha⁻¹, and by an additional 0·15 with the next increment of 50 kg N ha⁻¹. In the first year that directly followed N-fertilizer applications, DM yield was 0·175 higher than the no fertilizer treatment when 50 kg ha⁻¹ had been previously applied and a further 0·16 higher when 100 kg ha⁻¹ had been previously applied. Dry matter yields were greater from the one-cut than the two-cut regime only in years when no N-fertilizer was applied. Knife placement of N-fertilizer increased total DM yield only at 100 kg N ha⁻¹. Tiller densities were generally higher under the one-cut than the two-cut regime, particularly when N-fertilizer was broadcast. The application of N-fertilizer increased herbage production, especially when responses in the year subsequent to application are considered.     

Shoot development and flowering in potato (Solanum tuberosum L.)

Summary The shoot system of potato is a configuration of stems with terminal inflorescences. In this review, shoot development is quantified in terms of stem production, while stem development is quantified in terms of leaf and flower primordia production per stem, which are functions of the rates and the durations of primordia initiation. The effect of the position of the stem in the shoot system on number of leaves and flowers per stem is also evaluated. Flowering of individual stems is described by the ‘time to flower primordia initiation’ (expressed in number of leaves produced) and ‘flower production’ (a function of the number and the development of flower primordia). At warmer temperatures and longer daylengths the number of leaves and flower primordia per stem, and the number of stems per shoot increase by prolonging stem production and primordia development. Temperature and photoperiod also affect flower primordia survival by altering assimilate production and partitioning. The photothermal response of the number of leaves per stem is small compared to the response of stem production; at higher temperatures, flower primordia survival becomes the principal factor determining flower production. The similarity of the signals leading to flower primordia initiation and tuberization, and the relation between shoot and tuber growth are discussed.     

Comparison of light- and temperature-based index models for potato (Solanum tuberosum L.) growth and development

Robust and simple methods of normalizing for the weather of particular growing seasons enable improved in-season decisions, such as supplemental fertilizer timing. Common methods involve expressing the progress of the season in terms of degree-days or cumulative incident solar radiation, in contrast to days after planting or emergence. This study compared a newly introduced temperature-derived variable, “relative thermal index” (RTI) based on a modified beta distribution model, with growing degree day (GDD), physiological day (Pday), and cumulative photosynthetically active radiation (PAR), for their ability in normalizing for seasonal differences in growth and development of well-managed commercial potato fields of cvs Russet Burbank and Russet Norkotah in humid, temperate central Wisconsin. The proposed RTI was superior to all other investigated variables in reducing the standard deviation of crop mass among field-years through full canopy development, after which PAR became the more powerful normalization. Values of 15, 27, and 30 RTI corresponded to tuber initiation onset, canopy full interception of light, and tuber-bulking onset, respectively, for both varieties; RTI values were more consistent across the two varieties for these stages than were other variables. Presumably RTI was superior to other thermal time indices because it more appropriately reflected the dependence of potato growth rate on relatively cool temperatures.     

Optimizing the propagation of potato (Solanum tuberosum L.) by stem cuttings

Stem cuttings from potato plants are frequently used in multiplication programs for disease-free cultivars. The survival of these leafy cuttings is often very poor, and thus various techniques were investigated which were designed to increase rooting and cutting survival. Stock plants of cultivars “Caribe,” “Jemseg,” “Keswick,” “Russet Burbank,” “Sable,” “Sebago” and “Shepody” were grown in the greenhouse under long days. Promoting growth of the axillary shoots was successfully achieved by shading the shoot apex with aluminum foil. Trimming the outer leaves of the cuttings was deleterious to both survival and rooting. A rooting hormone improved root initiation and development, and the use of shade cloth or intermittent mist increased survival by reducing wilting. A rooting substrate of vermiculite: perlite (1:1) provided sufficient aeration, support and drainage for the cuttings. Antitranspirants sprayed on the stock plants prior to the excision of cuttings and also on the excised cuttings did not improve rooting or survival. The addition of activated charcoal (1% w:w) increased rooting of the cuttings and improved vigor of potted plants obtained from the cuttings.     

Correlation studies on 1000-true-seed weight,tuber yield and other morphological traits in potato (Solanum tuberosum L.)

Summary Simple phenotypic, genotypic and environmental correlation coefficients were calculated from one year's data for nine characters in F₁ seedlings of 72 crosses and 18 parents of potato (Solanum tuberosum L.). Crosses were made in a line x tester model having 12 female lines and six male testers. The experiment was designed as a randomized block replicated three times at Kufri, Simla (India) during the 1979–80 crop season. Positive phenotypic and genotypic correlations of 1000-TPS weight were found with total tuber yield, number of leaves on the main shoot, number of shoots per plant and harvest index. The results suggest that 1000-TPS weight could be used when attempting to select for yield and other characters in F₁ seedlings. Adapted from a thesis submitted and approved for the degree of Doctor of Philosophy of Agra University.     

Studies of the evaluation of different genotypes of potato (Solanum tuberosum L.) for yield and mineral contents

Six genotypes of potato were compared with two commercial cultivars, Kufri Chandramukhi and Kufri, Chamatkar for their yield and mineral contents (i.e., iron, copper, zinc, sodium, calcium, magnesium and phosphorus). There were significant differences amongst different genotypes with respect to yield and mineral contents. The cultivar Kufri Chandramukhi, which gave also significantly highest tuber yield during both years, was found to be richest in copper, zinc and potassium. The genotypes EM/B-1601 and JF-4835 were found to be highest in iron content. The highest quantities of sodium, potassium, and magnesium were detected in the cultivar Kufri Chamatkar. The genotype J.F. 5106 was also found to be rich in magnesium content which was comparable to Kufri Chamatkar. The highest quantities of phosphorus and calcium were found in genotypes J.F. 4835 and EM/B-859 respectively. The genotype J.F. 547 was found to be poorest in iron, copper, zinc, sodium and potassium.     

Water relations of the potato (Solanum tuberosum L.) cultivars Raritan and Shepody

Physiological responses to drought stress were evaluated in the potato cultivars Raritan and Shepody. Under well-watered conditions, Raritan exhibited a higher transpiration rate than Shepody. This higher rate could be related to a lower calculated stomatal resistance on abaxial leaf surfaces. Under drought stress conditions, Raritan consistently demonstrated superior performance over Shepody in the following areas: leaf water retention, epicuticular wax levels, desiccation tolerance and root growth. The estimated relative water content at a leaf water potential of-1.0 MPa was higher for Raritan than Shepody regardless of leaf age and may indicate a greater drought resistance in the former cultivar.     

Suppression of marker genes in sequentially transformed potato (Solanum tuberosum L.)

Transgenic potato lines were developed from the advanced selection, ND860-2, by sequential transformation usingAgrobacterium tumefaciens and two different constructs. Five doubly-transformed lines were utilized to study gene expression of the first construct. Three doubly-transformed lines had less NPT II antigen than the singly-transformed counterpart from which each was derived. GUS activity was reduced in all doubly-transformed lines compared to their singly-transformed original genotypes. Therefore, NPT II and GUS genes in the first construct were suppressed to varying degrees by a second construct. Further investigations into this important subject will be necessary to enable multiple transformations with genes of agronomic interest.     

Influence of plant spacing on potato (Solanum tuberosum L.) morphology,growth and yield under two contrasting environments

Summary In experiments at a temperate (43^oN) and a tropical (14^oN) location, closer plant spacing decreased stem branching, root growth, and mean tuber size but increased tuber yields per ha. Closer spacing increased plant height at the temperate site but decreased it at the tropical site where canopy cover did not reach 100%. The increased branching at the wider spacing did not compensate for fewer plants/m². Total and tuber weight per plant increased with wider spacing and was much greater under temperate than tropical conditions. Tuber yield/stem also increased with lower stem densities. Although these results provide initial data for modelling, the contrast between the two environments and interactions between spacing and cultivar suggest that further experiments need to be done with a range of cultivars at intermediate locations.     

The effects of nitrogen supply and stem density on leaf attributes and stem branching in potato (Solanum tuberosum L.)

Summary The interaction between nitrogen supply and stem density on leaf attributes and branching was studied in two field experiments. Stem densities included 8, 16, 24, 32 and 40 stems m⁻². The low-N treatments received 5 or 10 g m⁻² nitrogen, and the high-N treatments 20 or 25 g m⁻². The sizes of mature individual leaves on the main stem declined with increase in stem density and were larger for greater N supply, with additive effects of nitrogen and stem density. The specific leaf area was not affected by nitrogen supply and increased with stem density (range of values: 210 to 310 cm² g⁻¹). The leaf weight ratio was not affected by the treatments. At 8 and 16 stems m⁻² basal branches contributed substantially to the total leaf area per stem: at 24 stems m⁻² and higher densities the development of basal branches was negligible. Leaf area on apical branches was always smaller for higher plant densities and lower rates of N supply.     

利用分子标记鉴定四川省马铃薯品种

以15个马铃薯育成品种和引进品种为材料,采用微卫星分子标记技术鉴定供试马铃薯品种。研究检测了4个SSR位点在15份马铃薯育成品种(系)中的多态性。在15份马铃薯品种(系)中,共检测到等位基因26个,每对引物检测到的等位基因个数最少为5个,最多为10个,平均6.5个。PIC(Polymorphism information content)值最高为0.9288;最低为0.8597,平均PIC值为0.8857。仅利用少数几对高PIC值的SSR引物,即能将全部供试品种(系)区分,因此,SSR技术有利于高效准确的鉴定马铃薯品种。     

氮素形态与马铃薯品质的关系

在田间条件下研究了不同形态氮素对马铃薯块茎硝酸盐含量、淀粉、蛋白质及还原糖含量的影响。结果表明,马铃薯块茎内硝酸盐含量从块茎形成期到成熟收获期是逐渐降低的。使用铵态氮肥并加硝化抑制剂双氰胺可以显著地抑制马铃薯块茎硝酸盐的积累;与硝酸盐含量变化相似,从块茎形成期到收获期蛋白质含量也逐渐降低,不同氮素形态处理对马铃薯块茎内蛋白质含量的影响无显著差异;铵态氮添加双氰胺处理可降低块茎还原糖含量。虽然马铃薯被认为是喜硝作物,但本研究表明,不同氮素形态处理不仅没有造成马铃薯产量的显著差异,而且块茎内淀粉含量也无显著差异。     

Effects of growth regulators on the growth and yield of detached and transplanted potato (Solanum tuberosum L.) sprouts

Summary Roots of 15-day-old sprouts detached from tubers of potato (Solanum tuberosum L.) cv., Local Red, were dipped for 1 min in a 0.25% solution of Ethrel (ethephon), Rootone-F (RF), or Transplantone (TP) or in water and then planted in the field. Plants treated with RF and TP were significantly (P<0.05) taller, had heavier haulm, produced more leaves, and yielded more tubers than those of the control treatment with water, ethephon had no effect. RF was significantly (P<0.05) superior to TP for all measured components except leaf number.     

Unsaponifiable lipids from haulm and tuber sprouts of potato (Solanum tuberosum L.)

Summary Fractions containing Δ⁵- and Δ⁷-sterols, 4-methyl-sterols, triterpenic alcohols, tocopherols and hydrocarbons were isolated by TLC from petroleum ether extracts of the haulm and tuber sprouts of cv Désirée. Sterol and triterpenic alcohol fractions of unsaponifiable lipids of the haulm and tuber sprouts were found to contain twelve sterols and four triterpenic alcohols, respectively. 24R-4-stigmasten-3-on, Δ⁷, Δ⁷, lanosterol, cycloeucalenol and obtisufoliol have not been identified previously in unsaponifiable lipids from haulm and sprouts. In the hydrocarbon fractions of the haulm extract, C₂₃-to C₃₃-n-parafins, C₁₉-and C₃₁-cyclohexyl hydrocarbons, C₂₂-to C₃₈-olefins and squalene were identified, and in the hydrocarbon fractions of the tuber sprouts C₁₂-to C₂₆-olefins and squalene were identified.     

Varietal and environmental effect on the glycoalkaloid content of potato (Solanum tuberosum L.)

The tubers of 14 potato varieties were analysed for glycoalkaloids. The level of glycoalkaloids in tubers of all the varieties analysed are within the safe limits for human consumption. The peels of tuber contained about 60–70% of the total glycoalkaloids present in the whole tuber. The levels of glycoalkaloids in leaves and tubers were correlated (r=0.865). There was a significant increase in the content of glycoalkaloids in peels of tubers exposed to sunlight. Glycoalkaloid contents increased at the rate of 1.9mg/100g fresh weight per day in peels of Kufri Jyoti tubers exposed to diffused sunlight.     

Cryopreservation of in vitro-grown meristems of potato (Solanum tuberosum L.) by encapsulation-vitrification

Summary Alginate coated meristems from in vitro-grown axillary buds of potato (Solanum tuberosum L.) were successfully cryopreserved by vitrification. Excised meristems were precultured on sucrose-enriched MS medium and then encapsulated. To induce dehydration tolerance (osmotolerance), encapsulated meristems were treated with a mixture of 2 M glycerol plus 0.6 M sucrose for 90 min. These encapsulated meristems were dehydrated with a highly concentrated vitrification solution (PVS2 solution) for 3 hr at 0°C prior to a plunge into liquid nitrogen. Successfully vitrified meristems developed shoots within 3 weeks after plating without intermediary callus formation. The average rate of shoot formation amounted to nearly 70%. No difference was observed in RAPD analysis using 17 primers between cryopreserved and non-treated plantlets. The cryogenic protocol was successfully applied to 14 cultivars. It was also confirmed that the encapsulated vitrified meristems produced much greater shoot formation than the encapsulated dried meristems. Thus, the encapsulation vitrification protocol appears promising for cryopreservation of potato germplasm.     

A rapid screening technique for drought resistance in potato (Solanum tuberosum L.)

Summary The reduction in growth in the dark of leaf dises floated over polyethylene glycol 6000 solution of water potential −0.4 MPa, relative to the growth of similar leaf dises floated over water for the same period, varied in the range 10–87% in 28 genotypes. The growth reductions in the genotypes tested were in general agreement with what is known about their drought resistance. Publication No. 906, Central Potato Research Institute, Simla.