Variation among Species in Light Activation of Sucrose-Phosphate Synthase

Some species exhibit light activation of sucrose-phosphate synthase(SPS) in intact leaves. Twelve species which vary in extentof light modulation of SPS were studied to identify factorswhich regulate activation of the enzyme in situ. Leaves wereharvested in light and darkness, and SPS was assayed under highsubstrate (Vmax) or limiting substrate conditions (in the presenceof th inhibitor inorganic phosphate). The species tested fellinto three groups. In some species (Group I; barley and maize)light activation involved an increase in Vmax of the enzyme.In other species (Group II; spinach, swiss chard, sugarbeet,broad bean) light activation had no effect on Vmax but alteredcertain kinetic properties such that activation was only apparentwhen SPS was assayed with the limiting substration condition.Significantly, in some species (Group HI; soybean, pea, tobacco,Arabidopsis thaliana cucumber and melon) SPS activity was essentiallyunaffected by light/dark transitions. Phosphate sequesteringagents (mannose or gluco-samine) activated SPS in darkness inspecies which show light modulation (Groups I and II) but notspecies of Group III which do not light activate. Thus, changesin inorganic phosphate level may be one of the factors whichregulate the activation of SPS in situ. In addition, the catalyticactivity of SPS from species which exhibit light modulation(Groups I and II) is more strongly inhibited in vitro by inorganicphosphate (an allosteric effector) compared with the enzymeextracted from Group III species, which indicates that certainproperties of the enzyme itself may also vary among species.We conclude that species which do not exhibit light activationof SPS in intact leaves lack the mechanism responsible for thecovalent modification of enzyme activity (Walker and Huber 1989,Planta, in press) involved in light activation process. (Received October 14, 1988; Accepted January 5, 1989)     

Effect of Potassium on Potato Microtuber Production in vitro

The role of potassium nutrition in microtuber production was investigated in two potato cultivars belonging to different maturity groups. Alterations were made in Murashige and Skoog (MS) medium to obtain seven concentrations of potassium (10, 15, 20, 25, 30, 35 and 40 mM), and their effects were studied on microtuber number, microtuber mass and harvest index. In late cultivar Kufri Sindhuri, an increase in potassium concentration beyond 25 mM decreased the number of microtubers. Whereas, potassium did not show any inhibitory effect on microtuber number in early cultivar Kufri Ashoka. Potassium showed promoting effect on microtuber mass in both the cultivars. Maximum microtuber mass and harvest index were observed when the medium was supplemented with 40 mM potassium. Therefore, large size potato microtubers amenable to direct field planting can be induced in MS medium containing 40 mM potassium. This revised version was published online in July 2006 with corrections to the Cover Date.     

马铃薯晚疫病抗病基因研究进展

马铃薯晚疫病是马铃薯和番茄等茄科植物中最主要的病害之一,每年都引起巨大的经济损失。基因工程技术的发展为马铃薯晚疫病的防治工作提出了新的契机,从晚疫病抗性品种中筛选出具有高持久抗性的抗病基因,并将其转化到栽培品种中去,无疑是我们开发持久性晚疫病抗性的最快捷的手段。到目前为至,已经有十几个晚疫病抗性基因从S．demissum,S. bulbocastanum,S．berthauhii,S．mochiquense和S．pinnatisectum等抗性马铃薯品种中鉴定出来并已定位在马铃薯染色体基因组上,并有4个被克隆出来（R1,R3a,Rpi—blb1／RB和Rpi—blb2）。主要概述了马铃薯晚疫病抗病基因的研究现状和发展前景。     

内蒙古中部地区马铃薯根际和根系丛枝菌根真菌类群的多样性

【背景】丛枝菌根真菌(arbuscular mycorrhizal fungus,AMF)是菌根真菌中分布最广泛的一类真菌,能够与90%以上的植物形成菌根共生体,并通过调节宿主体内的代谢活动增强植物的抗逆性。【目的】揭示内蒙古马铃薯主产区土壤中AMF的结构与组成,解析马铃薯不同发育阶段以及连作对AMF类群的影响。【方法】以内蒙古中部地区大井村、徐麻夭村和红格尔图村采集的马铃薯根系及根际土为材料,通过PCR扩增建立18S rRNA基因文库,研究不同地点、不同马铃薯生育阶段以及连作对马铃薯根系内和根际土中的AMF类群组成和多样性的影响。【结果】大井村和红格尔图村马铃薯根际土中的AMF的类群多样性优于徐麻夭村,其中Glomus为大井村和红格尔图村马铃薯根际土样本中AMF的优势菌群,而徐麻夭村样本根际土中的优势类群为Diversispora。马铃薯根系中的AMF多样性的研究结果表明,3个供试地点根系内AMF类群的类型没有显著差异,但是AMF类群的比例却不同。大井村根系样本中AMF的优势菌为Diversispora,而Rhizophagus是红格尔图村和徐麻夭村根系样本中的优势AMF类群。同一供...     

Qualitative and Quantitative Analysis of Endogenous Jasmonoids in Potato Plant (Solanum tuberosum L.)

Qualitative and quantitative analyses of endogenous jasmonoids were done by liquid chromatography/selected ion monitoring (LC-SIM) using deuterium-labeled compounds as internal standards. To prove the practicality of this way of analyzing the contents of endogenous jasmonoids in plants, the method was used for estimating jasmonoids in potato plants.     

马铃薯（Solanum tuberosum L.）茎尖的超低温保存及其遗传变异的初步观察

研究马铃薯茎尖超低温保存技术的结果表明,4℃低温下锻炼6d,在添加二甲基亚砜（DMSO）和乙酰胺的培养基中预培养5d,60％PVS2于室温下装载30min,0℃下PVS2脱水40min时,茎尖成活率最高（71．6％）,再生植株生长分化正常。进一步对再生植株进行AFLP分析,6对引物组合共扩增出385条带,超低温保存前后的材料之间未见到明显差的异带,但用MSAP技术分析超低温保存前后植株甲基化的结果显示：超低温保存后的材料均有不同程度的甲基化。在扩增的624条带中,处理与否之间完全一致的带型为584条;有变化的带型为40条,处理2（茎尖经过完整的超低温保存过程,区别于处理1,增加了冷冻、解冻和洗涤后恢复培养）有13个位点的甲基化增加,21个位点去甲基化。     

Environmental Pollution and Relationship Between Total Antioxidant Capacity and Heavy Metals (Pb,Cd, Zn,Mn, and Fe) in Solanum tuberosum L. and Allium cepa L.

In the natural environment, plants are exposed to different stress factors that are responsible for overproduction of reactive oxygen species. Exposure to heavy metals is one of these factors. The present article highlights the correlation between the effects of bioaccumulation of heavy metals in a highly polluted region as the industrial zone of the Thermo Power Plants “Kosova” in Kosovo on the antioxidant capacity of two selected target species: Solanum tuberosum L. and Allium cepa L. The results show that environmental pollution in the industrial zone of the Thermo Power Plants “Kosova” generates a significant bioaccumulation of heavy metals such as Pb, Cd, Zn, Mn, and Fe. The high concentration of heavy metals leads to an increased production of reactive radical species. The extracts of target plants cultivated in this region display a lower antioxidant capacity than the same plants grown in a control rural area. The Fe bioaccumulation markedly influences the antioxidant capacity of plant samples analyzed.     

Changes in the Activity of Polygalacturonase-Inhibiting Protein during Potato Development

The activity of a polygalacturonase-inhibiting protein was determined in growing potato plants and in stored potato tubers. The activity in leaves was higher than in stems, and it decreased by the end of the vegetative season. During the dormancy period, the inhibitory activity in tubers also changed. In the sprouting tubers, it was somewhat lower than in the nonsprouting ones, and, in sprouts, it was usually higher than in tubers. Both the plant polygalacturonase and the polygalacturonase secreted by phytopathogenic fungi after their penetration in plant tissues can serve as inhibitor's targets. Therefore, the inhibitor seems to control the resistance of plants to infection by particular pathogens, and this resistance is characteristic of definite developmental stages.     

Production of potato intraspecific somatic hybrids with improved tolerance to PVY and Pythium aphanidermatum

Somatic hybridization can be an interesting alternative for the selection of heterozygous and vigorous potato plants through combination of dihaploid genomes. The resulting hybrids can harbour interesting characters and thus can be used in agriculture if they are in agreement with agronomic criteria.

In this report, we used an intraspecific somatic hybridization technique for the production of tetraploid potato lines. Two parental combinations were used in protoplast electrofusion procedure: Aminca-Cardinal and Cardinal-Nicola. The selection of somatic hybrids was based on in vitro plant vigour. Therefore, among the 75 regenerated plants obtained from Aminca-Cardinal fusion, 3 putative hybrids were retained and 2 plant lines were selected among the 54 regenerated from the Cardinal-Nicola fusion. Heterosis was observed in the larger hybrid tuber size compared to the parents’. Our results also showed a precocity in the in vitro tuberization for the hybrids. Moreover, all of the regenerated putative hybrids were tetraploid (2n=4x=48 chromosomes). Isocitrate dehydrogenase and malate dehydrogenase isoenzyme analyses confirmed the hybrid nature of these lines. A molecular characterization performed by PCR amplification of simple sequence repeats and inter-simple sequence repeats confirmed that all these lines were somatic hybrids.

The effect of potato virus Y infection on these hybrid lines was tested by mechanical inoculation of plants cultivated in a greenhouse. The majority displayed a reduction of infection rate associated with a delayed appearance of symptoms compared to the parents. Moreover, complete resistance was noted for one hybrid line (CN2). All hybrids also showed improved tolerance to Pythium aphanidermatum infection during tuber storage or after plant inoculation.     

Applications of biotechnology and genomics in potato improvement

Potato is the third most important global food crop and the most widely grown noncereal crop. As a species highly amenable to cell culture, it has a long history of biotechnology applications for crop improvement. This review begins with a historical perspective on potato improvement using biotechnology encompassing pathogen elimination, wide hybridization, ploidy manipulation and applications of cell culture. We describe the past developments and new approaches for gene transfer to potato. Transformation is highly effective for adding single genes to existing elite potato clones with no, or minimal, disturbances to their genetic background and represents the only effective way to produce isogenic lines of specific genotypes/cultivars. This is virtually impossible via traditional breeding as, due to the high heterozygosity in the tetraploid potato genome, the genetic integrity of potato clones is lost upon sexual reproduction as a result of allele segregation. These genetic attributes have also provided challenges for the development of genetic maps and applications of molecular markers and genomics in potato breeding. Various molecular approaches used to characterize loci, (candidate) genes and alleles in potato, and associating phenotype with genotype are also described. The recent determination of the potato genome sequence has presented new opportunities for genomewide assays to provide tools for gene discovery and enabling the development of robustly unique marker haplotypes spanning QTL regions. The latter will be useful in introgression breeding and whole‐genome approaches such as genomic selection to improve the efficiency of selecting elite clones and enhancing genetic gain over time.     

反义酸性转化酶基因低温贮藏马铃薯块茎还原糖和淀粉含量的影响

对2个含有酸性转化酶(AcInv)反义基因的转基因马铃薯品系及对照品种进行低温贮藏(4℃)及室温还暖处理.随低温贮藏时间的延长,供试材料均表现出还原糖含量升高,总淀粉含量下降的趋势.低温处理40 d时,"Ac转Atlantic"和"Ac转甘农薯2号"的还原糖含量比未转基因品种低23%和18%.总淀粉含量分别比未处理前下降约1.0%和1.3%,支链淀粉含量分别下降约1.4%和1.7%,淀粉直/支比明显低于对照,分别为0.29和0.38.块茎的石蜡切片显示,转基因块茎中深蓝色淀粉颗粒明显少于未转基因对照.另外,对低温贮藏的块茎室温还暖后,2个转基因品系的还原糖含量仍低于对照品种.实验结果证明反义AcInv基因对低温贮藏下块茎还原糖和淀粉含量具有下向调节作用.     

Sucrose utilization during potato microtuber growth in bioreactors

 Potato microtubers are used as pathogen-tested in vitro stocks for certified seed potato production. Microtubers grown in a rotating bioreactor grew at a faster rate when the medium was replaced frequently. Although the total microtuber number was not affected, the number of microtubers over 1 g quadrupled when 75% of the medium was replaced every 2 weeks when compared with no medium refreshment. Significantly slower microtuber growth rates resulted when a lower sugar concentration (40 g 1⁻¹ instead of 80 g 1⁻¹) was used or when a mixture of glucose and fructose replaced sucrose. Although high sucrose levels are necessary for optimal microtuber production, the sucrose supplied was rapidly hydrolyzed into glucose and fructose, making the long-term maintenance of desirable sucrose levels difficult. These results indicate that successful strategies to reduce sucrose hydrolysis without inhibiting microtuber growth will improve the efficiency of sucrose utilization in potato microtuber bioreactors. Received: 1 December 1998 / Revision received: 6 May 1999 · Accepted: 19 May 1999     

马铃薯离体再生及人工种子研究

马铃薯３个品种虎头,克４和Ｆａｖｏｒｉｔａ的茎叶外植体在ＭＳ＋１ｍｇ／ＬＮＡＡ＋１ｍｇ／ＬＢＡ培养基上形成愈伤组织。在ＭＳ＋０２ｍｇ／ＬＮＡＡ＋１ｍｇ／ＬＢＡ培养基上,愈伤组织分化产生不定芽。在ＭＳ＋００５ｍｇ／ＬＮＡＡ培养基上,不定芽生根形成再生完整植株。０２～０３ｃｍ大小的不定芽反复继代可持续增殖。有３个以上叶片的不定芽在ＭＳ＋５ｍｇ／ＬＢＡ＋００５ｍｇ／ＬＩＢＡ培养基上和黑暗条件下,在侧芽或顶芽部位形成微型薯。用４％海藻酸钠和２％氯化钙溶液包裹０２～０３ｃｍ大小的不定芽或直径为０２～０３ｃｍ的微型薯制成微芽人工种子和微薯人工种子。在４℃下贮存２个月后,微芽人工种子和微薯人工种子在有菌腐殖土壤中播种２１ｄ的萌发率分别是１５７％和９６２％。     

Induction of Phytohemagglutinin Activity by Arachidonic Acid in in vitro Potato Plants

Tube-grown potato (Solanum tuberosum L., cv. Nevskii) plants treated with arachidonic acid (AA) were used as a model to study the activity of phytohemagglutinins (PHA) during induction of the plant antiviral defense system. Plant treatment with 10^–8 M AA and also their inoculation with potato viruses X, Y, and M resulted in the increased activity of PHAs in potato shoots. The inducer of antiviral resistance behaved as a modulator of the PHA activity providing for its various levels during the development of viral infection. During the development of AA-induced systemic resistance, the level of phytohemagglutinin activity did not essentially depend on the nature of the viral pathogen. We suggested that the mechanism of AA-induced plant antiviral defense was connected with changes in the PHA activity.     

Effect of enhanced CaCl2, MgSO4, and KH2PO4 on improved in vitro growth of potato

Potato (Solanum tuberosum L.) is a major global food crop. Contemporary potato production largely utilizes micropropagation to produce healthy seed potatoes. The micropropagation of potatoes is widely achieved through nodal explants using the conventional Murashige and Skoog (MS) medium. Currently, effective culture media that can facilitate rapid propagation are increasingly required for new cultivars that have been developed to possess improved traits. In this study, we evaluated the effect of enhanced meso nutrients (CaCl₂.2H₂O, MgSO₄, and KH₂PO₄) in MS medium on the growth of S. tuberosum. The cultivars used in this study were representative of Japanese, European, and Peruvian lines. Enhanced meso nutrients improved the overall quality of all cultivars, as indicated by longer shoots and larger leaves with dark color, compared with MS medium only. Shoots grown on enhanced mesos were approximately 1.5 times longer than on MS medium. Quantitative ion analysis revealed that plantlets with improved shoot length and leaf quality in most cultivars had increased calcium, magnesium, potassium, and phosphorus uptake than plantlets on MS medium. The results suggest that the reduced iron uptake on 3.0×MS, compared with 2.0× or 2.5×MS mesos, reduced plant growth. This study revealed for the first time that mesos concentrations higher than MS medium concentrations, complemented by enhanced calcium, magnesium, potassium, phosphorus, and iron uptake, play a significant role in improving the in vitro growth of potato.     

Genome selection within cell cultures of potato and tobacco

The ploidy level of callus cultures, suspensions and cell cultures derived from single cells and protoplasts of Solanum tuberosum L. and Nicotania tabascum L. was analysed with the aim of studying selection processes. Genome selection was tested using chromosome number. Subculture of callus lines mostly resulted in an increase of cytogenetic destabilization, whereas subculture of suspensions led to an increase in nuclei which had the ploidy level of stock plants after an initial period of destabilization. During the course of subculture, the development of a dominant ploidy level was observed in some genotypes. In other genotypes, two dominant ploidy levels were found. Furthermore, the narrowing of the confidence interval indicated stabilizing selection. In genotypes showing a high rate of instability, no development of a dominant genome was observed. The in vitro procedure is of decisive importance for genome selection within cell cultures. The interaction between genetic destabilization and genome selection is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Lipoxygenase Pathway and Membrane Permeability and Composition during Storage of Potato Tubers (Solanum tuberosum L. cv Bintje and Désirée) in Different Conditions

Abstract: Potato tubers ( Solanum tuberosum L. cv Bintje and Désirée) were stored for 12 months under three different storage conditions: 4 °C, 20 °C with sprout inhibitor and 20 °C without sprout inhibitor. Independent of the storage conditions, our results show that the increase of membrane permeability, as revealed by electrolyte leakage, is not correlated with the lipid saturation status. Moreover, there is no simple correlation between cold sweetening and membrane permeability or lipid saturation status. During storage at 20 °C without sprout inhibitor, the increase in membrane permeability is inversely correlated to sucrose accumulation, but this is not the case when tubers were stored with sprout inhibitors. Lipoxygenase (LOX) is often proposed as responsible for peroxidative damage to membrane lipids. The gradual peroxidation resulting in double bond index decrease is regarded as a cause of senescence sweetening. Our results revealed that the role of LOX in aging and senescence of potato tubers is far from clear. LOX activity and gene expression are not correlated with the fatty acids composition of the membrane. Moreover, LOX activity and fatty acid hydroperoxide content are low in older tubers, whatever the storage conditions or the varieties. On the basis of our results, the correlation between sugar accumulation (low temperature and senescence sweetening) and peroxidative damage occurring during storage of potato tubers is discussed.     

Exogenously applied jasmonic acid induces changes in apical meristem morphology of potato stolons

Hooked apex stolons and initial swelling stolons of potato plants were treated with 3 x 10-8 mol l-1 jasmonic acid (JA) to study the effect of this compound on histology, cell expansion and tissue differentiation. In hooked apex stolons, JA application increased the meristem thickness and reduced the length of the leaf primordia, whereas in initial swelling stolons narrowing of the apical region, absence of leaf primordia and swelling of the subapical meristem were evident. Early vascular tissue differentiation was observed in response to JA treatment, especially of xylem elements from regions proximal to the tunic. Protoxylem elements, such as tracheal elements, were present with thin primary cell walls. The cell area was measured in two zones: zone I, central mother cells situated immediately under the tunic; and zone II, rib meristem cells. JA caused a four- and six-fold increase in cell area in both zones in hooked apex stolons and initial swelling stolons, respectively. Thus, tuber formation is concluded to occur as a consequence of increased cell expansion, a reduction in the length of leaf primordia, enlargement of meristems, and early vascular tissue differentiation.