嘉兰块茎形成过程中物质变化的研究

嘉兰(Gloriosa superba L.)系百合科草本植物,其块茎含有秋水仙碱。本文研究块茎形成规律及其形成过程中物质变化。研究结果表明:块茎播后,新生的块茎在生长初期和后期生长速度都较慢,中期生长速度最快,也是嘉兰块茎产量形成的主要时期。块茎中营养物质主要是淀粉。新生块茎中淀粉含量,是随着新块茎的生长,其含量逐渐增高。叶片的光合速率和叶面积,从播后逐渐增加,开花前达到高峰,花后又逐渐降低。开花前如能增加光合叶面积,可为后期块茎生长提供较多物质。块茎中秋水仙碱含量是随着块茎的成熟与淀粉含量的渐增而增加,至收获期达到高峰。这一结果表明:收获未充分成熟的块茎,会降低秋水仙碱含量。     

Hormonal regulation of tuber formation in potato plants

Tuber formation is a complex process comprising several stages: stolon formation and growth, induction of tuberization, tuber initiation, and tuber growth. This review considers successive stages of tuber formation and their hormonal regulation. Special attention is paid to the effects on tuber formation of such phytohormones as gibberellins, cytokinins, jasmonic acid, and auxins. Physiological and some molecular-genetic aspects of their action on tuber photoperiodic induction and initiation are discussed.     

Interrelation Between Growth Rate of Individual Potato (Solanum tuberosum L.) Tubers and Their Cell Number

In potato plants fast and slow growing tubers develop on thesame plant. A hypothetical causality between tuber growth rateand tuber cell number was investigated by determining the tubercell number with the aid of an automatic counting procedure.Our data show a close correlation between tuber size and cellnumber over the whole range of tuber volumes considered (3–28cm³). If the influence of tuber size on cell number is eliminatedby means of a partial correlation analysis, the cell numberof the entire tuber is not significantly correlated with itsgrowth rate. An exclusive consideration of the smaller cells(10–30 µm) in the apical tuber region, where thecell division rate in potato tubers is highest, reveals a loosebut significant partial correlation to tuber growth rate (r= 0.383, P < 0.05). The growth rate of the slow growing tubers of any potato plantmay be enhanced by removing the fast growing tubers. In thefirst few days this enhanced growth rate is not due to a stimulationof cell division rate, but rather due to cell expansion. Potato, Solanum tuberosum L., tuber growth rate, tuber cell number     

马铃薯块茎发育机理及其基因表达

马铃薯（Solanum tuberosum L.)块茎是有块茎马铃薯植物的地下变态器官,它由匍匐茎顶端膨大形成,对于马铃薯块茎形成的生理机制已有许多研究,这些研究表明,块茎发生受许多因素的影响,总体来讲短日 照,较低的温度以及离体条件下培养基较高的蔗糖浓度等有利于块茎形成,同时,块茎形成过程中内源激素亦发生一系列变化,然而,对于块茎形成中相关基因表达,进而调控块茎形成的系统研究目前还较滞后,已有研究显示,块茎形成与膨大涉及到一系列基因的表达与关闭,同时它也与淀粉合成和块茎储藏蛋白基因的表达有关,综述了这一领域现有的研究进展。     

马铃薯块茎发育机理及其基因表达

马铃薯(Solanum tuberosum L.)块茎是有块茎马铃薯植物的地下变态器官,它由匍匐茎顶端膨大形成。对于马铃薯块茎形成的生理机制已有许多研究,这些研究表明,块茎发生受许多因素的影响,总体来讲短日照、较低的温度以及离体条件下培养基较高的蔗糖浓度等有利于块茎形成,同时,块茎形成过程中内源激素亦发生一系列变化。然而,对于块茎形成中相关基因表达,进而调控块茎形成的系统研究目前还较滞后。已有研究显示,块茎形成与膨大涉及到一系列基因的表达与关闭,同时它也与淀粉合成和块茎储藏蛋白基因的表达有关。综述了这一领域现有的研究进展。     

Comparative nutritional and mycochemical contents,biological activities and LC/MS screening of tuber from new recipe cultivation technique with wild type tuber of tiger’s milk mushroom of species <Emphasis Type="Italic">Lignosus rhinocerus</Emphasis>

Tiger’s milk mushroom is known for its valuable medicinal properties, especially the tuber part. However, wild tuber is very hard to obtain as it grows underground. This study first aimed to cultivate tiger’s milk mushroom tuber through a cultivation technique, and second to compare nutritional and mycochemical contents, antioxidant and cytotoxic activities and compound screening of the cultivated tuber with the wild tuber. Results showed an increase in carbohydrate content by 45.81% and protein content by 123.68% in the cultivated tuber while fat content reduced by 13.04%. Cultivated tuber also showed an increase of up to 64.21% for total flavonoid-like compounds and 62.51% of total β-d-glucan compared to the wild tuber. The antioxidant activity of cultivated tuber and wild tuber was 760 and 840 µg mL^?1, respectively. The cytotoxic activity of boiled water extract of cultivated tuber against a human lung cancer cell line (A549) was 65.50?±?2.12 µg mL^?1 and against a human breast cancer cell line (MCF7) was 19.35?±?0.11 µg mL^?1. β-d-glucan extract from the purification of boiled water extract of cultivated tuber showed cytotoxic activity at 57.78?±?2.29 µg mL^?1 against A549 and 33.50?±?1.41 µg mL^?1 against MCF7. However, the β-glucan extract from wild tuber did not show a cytotoxic effect against either the A549 or MCF7 cell lines. Also, neither of the extracts from cultivated tuber and wild tuber showed an effect against a normal cell line (MRC5). Compound profiling through by liquid chromatography mass spectrometry (LC/MS) showed the appearance of new compounds in the cultivated tuber. In conclusion, our cultivated tuber of tiger’s milk mushroom using a new recipe cultivation technique showed improved nutrient and bioactive compound contents, and antioxidant and cytotoxic activities compared to the wild tuber. Further investigations are required to obtain a better quality of cultivated tuber.     

我国油莎豆栽培品系表型特征的相关性分析

油莎豆(Cyperus esculentus L.)起源于地中海北非地区,是一种在块茎器官中储藏油脂的特殊油料作物。为了在我国推广油莎豆的种植,急需对我国油莎豆品系的基本生物学特性进行研究。我们收集了国内油莎豆主要种植地的种质资源(品系),经过大田种植后,比较分析了品系间块茎和植株部分性状及其相关性。根据块茎的大小和形态,将这些栽培油莎豆品系归为3个基本类型,即长粒型、大粒型和圆粒型。在大田种植条件下,油莎豆各品系都极少开花,品系之间块茎芽点数和茎环数无显著性差异。但是这3个类型油莎豆在块茎含油量、叶片和植株形态、分蘖特性等方面具有很大差异。叶片长宽比与块茎高宽比显著正相关,但叶片形态与块茎含油量的相关性不显著。该研究结果可为油莎豆的大田种植和品种选育提供重要参考。     

The Anatomy of the Root System in West Indian Sweet Potato (Ipomoea Batatas (L.) Lam.) Cultivars

The comparative anatomy of different root types including tuberousroots and tubers in the root system of a West Indian sweet potatocultivar cv. 049 is described, and tissue distribution in maturetubers compared with five other local cultivars. Anatomicalevents leading to tuber initiation and tuber growth to maturityare outlined and the anatomical specialization of the sweetpotato tuberous root, particularly in the development of translocatorytissues in the ‘tuber stalk’ and in adventitiousbud genesis, is described. Possible relationships between theanatomy of tuber development and final tuber yield are discussed.     

Allocation of Photosynthate to Individual Tubers of Solanum tuberosum L.: III. RELATIONSHIP BETWEEN GROWTH RATE OF INDIVIDUAL TUBERS, TUBER WEIGHT AND STOLON GROWTH PRIOR TO TUBER INITIATION

Potato plants (Solanum tuberosum L.) were grown in water culture.About 14 d after tuber initiation no significant differenceswere found between apical and basal tuber parts in ¹⁴C-uptakeand partitioning into various fractions from ¹⁴C-labelled photosynthate.Thus, the fresh weight of these tubers could be used as a parameterfor the sink size. The ¹⁴C-content per tuber (sink strength)20 h after ¹⁴CO₂-supply to the foliage was significantly correlatedwith the tuber fresh weight. No correlation was found betweenthe ¹⁴C-concentration of the tuber (sink activity; ct. min^–g^– fr. wt.) and tuber fresh weight. Consequently, tuberfresh weight (sink size) per se must have been a factor whichinfluenced sink strength. Stolon parameters characterizing theirgrowth prior to tuber initiation (e.g. stolon volume) and theircapacity for photosynthate transport (diameter, length) weremeasured at the time of tuber initiation. Significant correlationswere found between these stolon parameters and subsequent growthof individual tubers. Anatomical studies on the proportion ofvarious tissues in the cross sectional area of stolons supportthe idea of a negative relation between growth of individualtubers and transport resistance in the phloem of the stolons.It is concluded that in the initial phase of tuber growth, mainlyfactors outside of the tuber determine its growth rate. In laterstages of tuber growth, when the sink strength increases, thecompeting strength of individual tubers for photosynthate isdominated mainly by factors within the tuber itself, such astheir sink size and sink activity. Key words: Potato tuber, sink size, tuber initiation, transport resistance     

Comparative Analysis of Tuber Development in Six Sweet Potato (Ipomoea batatas (L.) Lam) Cultivars: 2. Interrelationships between tuber shape and yield

Interrelationships between tuber dimensions and yield duringdevelopment of six sweet potato cultivars with different tubershapes were examined. Maximum tuber lengths and tuber stalklengths were attained after 16 and 8 weeks of growth, respectively.Rates of increase in tuber width in the 16- to 24-week periodand final tuber widths were related to the mean tuber weightand yield of the cultivars studied, e.g. rates were highestin the high yielding cv. O₄₉ and low in cv. A16/15. Relationshipsbetween parameters of tuber development, tuber dimensions, sinkstrength and yield were evaluated and tuber width appeared tobe the most important single dimensional determinant of highyield. However, tuber shape in cv. 03/62 was different fromother cultivars and this cultivar was an exception in the interrelationshipsdescribed. Some factors known to affect tuber shape and developmentwere discussed.     

Early generation selection for agronomic characters in a potato breeding programme

Summary A random sample of seedlings representing high, medium and poor vigour was studied for tuber colour, tuber shape, eye depth, tuber cracking, tuber yield per plant, average tuber weight and number of tubers per plant in four successive generations (F₁, F₁, F₁C₂, and F₁C₃). Based on the performance of vigour groups in various generations and inter-generation correlation coefficients, we propose a procedure for the elimination of unproductive genotypes early in the breeding programme. The data indicates that seedlings of poor vigour can be discarded at the seedling stage prior to transplantation in the field. The rejection of clones on the basis of tuber colour, tuber shape, eye depth and tuber cracking can also be initiated at the seedling stage. For tuber yield and average tuber weight a negative selection (rejection of poor phenotypes) is suggested from the first clonal generation and for number of tubers, from second clonal generation, until statistically sound replicated trials can be conducted for carrying out positive selection.     

StGA2ox1 is induced prior to stolon swelling and controls GA levels during potato tuber development

The formation and growth of a potato ( Solanum tuberosum ) tuber is a complex process regulated by different environmental signals and plant hormones. In particular, the action of gibberellins (GAs) has been implicated in different aspects of potato tuber formation. Here we report on the isolation and functional analysis of a potato GA 2-oxidase gene ( StGA2ox1 ) and its role in tuber formation. StGA2ox1 is upregulated during the early stages of potato tuber development prior to visible swelling and is predominantly expressed in the subapical region of the stolon and growing tuber. 35S-over-expression transformants exhibit a dwarf phenotype, reduced stolon growth and earlier in vitro tuberization. Transgenic plants with reduced expression levels of StGA2ox1 showed normal plant growth, an altered stolon swelling phenotype and delayed in vitro tuberization. Tubers of the StGA2ox1 suppression clones contain increased levels of GA₂₀, indicating altered GA metabolism. We propose a role for StGA2ox1 in early tuber initiation by modifying GA levels in the subapical stolon region at the onset of tuberization, thereby facilitating normal tuber development and growth.     

A role for symplastic gating in the control of the potato tuber life cycle

The control of the potato tuber life cycle has been the subject of significant interest over many years. A number of different approaches have been adopted and data is available regarding hormonal, metabolic and gene expression changes that occur over the tuber life cycle. Despite this intense effort, no unifying model for the control of the potato tuber life cycle has emerged. We have undertaken a detailed analysis of the tuber life cycle utilising physiological, biochemical and cell-biological techniques. It has emerged that a major factor contributing to both tuber induction and dormancy break is symplastic gating which controls the allocation of resources to meristematic or vegetative tissues. Future challenges include the determination of factors regulating symplastic gating at the molecular level and the extrapolation of these findings to other systems.Key words: development, tuber, potato     

Tuber on a chip: differential gene expression during potato tuber development

Potato tuber development has proven to be a valuable model system for studying underground sink organ formation. Research on this topic has led to the identification of many genes involved in this complex process and has aided in the unravelling of the mechanisms underlying starch synthesis. However, less attention has been paid to the biochemical pathways of other important metabolites or to the changing metabolic fluxes occurring during potato tuber development. In this paper, we describe the construction of a potato complementary DNA (cDNA) microarray specifically designed for genes involved in processes related to tuber development and tuber quality traits. We present expression profiles of 1315 cDNAs during tuber development where the predominant profiles were strong up- and down-regulation. Gene expression profiles showing transient increases or decreases were less abundantly represented and followed more moderate changes, mainly during tuber initiation. In addition to the confirmation of gene expression patterns during tuber development, many novel differentially expressed genes were identified and are considered as candidate genes for direct involvement in potato tuber development. A detailed analysis of starch metabolism genes provided a unique overview of expression changes during tuber development. Characteristic expression profiles were often clearly different between gene family members. A link between differential gene expression during tuber development and potato tissue specificity is described. This dataset provides a firm basis for the identification of key regulatory genes in a number of metabolic pathways that may provide researchers with new tools to achieve breeding goals for use in industrial applications.     

A new method for on-line measurement of diurnal change in potato tuber growth under controlled environments

An on-line laser micrometer system was applied to measurement of diurnal change in potato (Solanum tuberosum L.) tuber growth. Diameters of the potato tuber were scanned by moving a laser micrometer along the longitudinal axis of the tuber at constant speed, and tuber volume was evaluated as an aggregate of thin discs. A single potato tuber, without competitive sink tubers in the plant, was grown in controlled air at 20 degrees C and 80% RH, and tuber volume was measured at 30 min intervals. During the growth experiment, the potato tuber increased in size without any inhibitory effect of periodical laser beam irradiation. Greatest expansion generally occurred during the early night, and transient contraction of the tuber occurred at the beginning of the light period.     

Construction of a dense SNP map of a highly heterozygous diploid potato population and QTL analysis of tuber shape and eye depth

Key message

Generation of a dense SNP-based linkage map of a diploid potato population and identification of major QTLs for tuber shape and eye depth on chromosomes 2 and 10.

Abstract

This paper reports the construction of a genetic map of a highly heterozygous full-sib diploid potato population (06H1) based on the use of a set of 8,303 single nucleotide polymorphism (SNP) markers. The map contains 1,355 distinct loci and 2,157 SNPs, 802 of which co-segregate with other markers. We find high levels of collinearity between the 12 chromosomal maps with a recently improved version of the potato genome assembly, with the expected genetic clustering in centromeric regions. The linkage maps are used in combination with highly detailed phenotypic assessments conducted over two growing seasons to perform quantitative trait loci analysis of two important potato traits, tuber shape and eye depth. The major loci segregating for tuber shape in 06H1 map to loci on chromosomes 2 and 10, with smaller effects mapping to three other chromosomes. A major locus for tuber eye depth co-locates with the tuber shape locus on chromosome 10. To assess when tuber shape is established in the developing tuber, we have performed staged observations of tuber formation. Our observations suggest that tuber shape is determined very early in tuber development.     

Pectin engineering to modify product quality in potato

Although processed potato tuber texture is an important trait that influences consumer preference, a detailed understanding of tuber textural properties at the molecular level is lacking. Previous work has identified tuber pectin methyl esterase (PME) activity as a potential factor impacting on textural properties, and the expression of a gene encoding an isoform of PME (PEST1) was associated with cooked tuber textural properties. In this study, a transgenic approach was undertaken to investigate further the impact of the PEST1 gene. Antisense and over-expressing potato lines were generated. In over-expressing lines, tuber PME activity was enhanced by up to 2.3-fold; whereas in antisense lines, PME activity was decreased by up to 62%. PME isoform analysis indicated that the PEST1 gene encoded one isoform of PME. Analysis of cell walls from tubers from the over-expressing lines indicated that the changes in PME activity resulted in a decrease in pectin methylation. Analysis of processed tuber texture demonstrated that the reduced level of pectin methylation in the over-expressing transgenic lines was associated with a firmer processed texture. Thus, there is a clear link between PME activity, pectin methylation and processed tuber textural properties.