Root influence on shoot development in tea (Camellia sinensis (L.) O. Kuntze) following shoot pruning

The physiological interaction between the factors controlling the development of new shoots in pruned tea plants was investigated in an experiment using a widely cultivated TRI clone growing at low elevation in Sri Lanka. The functional importance during new shoot growth of root reserves, feeder roots and leaves and buds on unpruned branches (lung-shoots) is critically evaluated. A scheme for their interaction is presented, which highlights the need to maintain feeder roots alive during new shoot development, for which a large proportion of both reserve and current assimilates seem to be utilized. Mature leaves on lung-shoots, besides supplementing carbohydrate supply by current photosynthesis, may also serve to maintain the flow of metabolites from feeder roots to developing shoots and also function as ‘sinks’ for excess, toxic levels of root metabolites. Removing all mature leaves, as is done during ‘clean pruning’, leads to the depletion of reserves below the critical level for feeder root survival, resulting in death of feeder roots and failure of new buds to form shoots.     

茶树品种资源遗传多样性的AFLP研究

 利用AFLP - 银染分子标记技术, 对40个茶树品种(系) 进行遗传多样性与亲缘关系分析。选用多态性高、分辨力强的引物组合E-ACG/M-AAC、E-AGG/M-AAG与E-AGG/M-AGT分别对供试材料的基因组DNA进行扩增, 共获得226条清晰可辨的带, 其中多态性带207条, 多态位点百分率为91.59% ,这表明供试品种资源在DNA水平上酶切位点的分布存在广泛的变异。40份资源所检出的位点平均有效等位基因数、平均基因多样度、平均Shannon信息指数, 分别为1.59 ±0.09、0.35 ±0.04、0.53 ±0.05。应用SPSS软件计算遗传距离介于0.13～0148之间, 平均为0.32; UPGMA法将40份资源分成4个类群, 从相似性系数分析了各品种资源间的亲缘关系。     

The effect of node origin on the development of cuttings of the tea plant (Camellia sinensis (L.) O. Kuntze)

The growth of roots and shoots of cuttings taken from nodes 3 to 9 on the parent stem, counting from the apex, have been compared. Comparisons also included dry weight of parts of the cuttings and leaf areas.

The number of cuttings with roots was unaffected by node origin; the weight of roots was similarly unaffected with the exception of one doubtful case.

Shoot growth, on the contrary, was found to be much more advanced in cuttings from older nodes, presumably because the buds were more highly developed. The cutting buds produced the flush-type growth and leaf forms typical of a mature tea bush.

The effect of node position on dry weights of cuttings was irregular. The greater loss of original leaves among cuttings from older nodes appeared to counteract the expected greater dry weight of these cuttings.     

Direct somatic embryogenesis from explants obtained from in vitro germinated embryonic axes of Camellia sinensis (L.) O. Kuntze

Summary

Studies on direct somatic embryogenesis in several types of explant from in vitro plantlets of tea cultivar TRI 2025 were undertaken to select those most suitable to induce cotyledonary-type somatic embryos. Mature zygotic embryonic axes were surface-sterilised and cultured on MS medium without growth regulators containing 0.6% (w/v) agar. Results showed that 65% of embryonic axes that converted into plantlets at the fifth week of culture had succulent leaves. Several types of explant (normal leaves, large and small succulent leaves, hypocotyl segments and root tips) were isolated from in vitro plantlets at the fifth week and cultured on half-strength MS medium containing 2 mg l^–1 6-benzylaminopurine (BAP) and 0.2 mg l^–1 naphthalene acetic acid (NAA). Morphological and histological observations on somatic embryogenesis were made. The results indicated that somatic embryos were produced at high frequency (25 – 50%) directly from the surface of hypocotyl segments (HS) and large succulent leaves (LSL) after 6 weeks of culture. Efficient somatic embryogenesis was induced in small succulent leaves (SSL) after 16 weeks. Most somatic embryos originated directly from the cortical tissues of HS or the upper epidermal layers of SSL or LSL. HS and SSL from in vitro plantlets gave the highest production of typical, firm somatic embryos for use in tea improvement programmes and for in vitro conservation of tea germplasm.     

Effects of pruning time and resting period on total non-structural carbohydrates,regrowth and yield of tea (Camellia sinensis L.)

Summary

An experiment was conducted at Kipkebe Estate, Sotik, Kenya, with the aim of establishing the effects of pruning time and resting period on total non-structural carbohydrate (TNC) reserves, regrowth and yield of tea. In this experiment, tea bushes were freely left unplucked for 45 and 90.d before pruning. Control treatments were continuously plucked until pruning. Results showed that TNC was significantly (P≤0.05) increased at pruning time. October pruning significantly increased leaf, stem, and root TNC. A longer resting period of 90.d significantly increased leaf and root TNC to 294 and 230.gkg^–1, respectively. Generally, TNC declined after pruning and thereafter increased. Root TNC significantly correlated with regrowth period, diebacks and yield. Generally, the best resting period for increased TNC, regrowth and yield, is between 45 and 90.d. The best pruning time is October, if drought stress can be avoided.     

Observations on the Winter Dormancy of tea (Camellia Sinensis L.) in Malawi

In Malawi, over 80 % of the tea yield is harvested during the five months of the hot, wet, tropical summer. Characteristics of shoot growth were examined to define the nature of the fall in yield during the subsequent winter months of May to August. Slower shoot extension and more apical bud dormancy reduced the rate at which shoots reached harvestable size in winter. No changes were observed in other characteristics of shoot growth such as individual shoot weight, shoot death or dormancy of the axillary buds in their initial state. During the winter there was a stimulation of root growth and the low yield was possibly related in part to a redistribution of assimilate. Altering the photoperiod had little effect on yield but maintenance of warm night temperatures (20°C) during parts of the cold season accelerated the rate of shoot growth to a level as high as that of the hot, wet season.     

Genotypic variation in biochemical compounds of the Sri Lankan tea (Camellia sinensis L.) accessions and their relationships to quality and biotic stresses

Tea (Camellia sinensis L.) is well known for its biochemical constituents that define the product quality and confer pest and disease resistance. Seven major metabolites – epicatechin (EC), epicatechin gallate (ECg), epigallocatechin (EGC), epigallocatechin gallate (EGCg), caffeine, theobromine, and gallic acid – of 87 beverage type and six non-beverage type tea accessions from Sri Lankan tea germplasm were profiled using HPLC and LC-MS/MS. All seven metabolites varied widely in the beverage type accessions. The non-beverage types only contained gallic acid and epicatechin. Results prove the presence of high EC and ECg contents in green leaves to be a reliable marker for identifying high-quality black tea-producing accessions. High EC and low EGCg contents in green tea leaves appear to enhance traits of resistance to blister blight disease. Significant variations detected in theobromine, caffeine, and total polyphenol content define the affinity of germplasm to the main three tea taxa, and we conclude that C. sinensis ssp. lasiocalyx predominates the Sri Lankan germplasm collection.     

Photosynthesis and assimilate partitioning during rhythmic growth of green tea (Camellia sinensis var sinensis)

Summary

Shoot morphogenesis in green tea was used to define key events in development which occur during rhythmic growth. These stages are: stage I, no shoot extension or leaf expansion with a maximum number of leaf primordia in the apical bud; stage II, maximum shoot extension and leaf expansion; stage III, cessation of shoot extension and leaf initiation; and stage IV, cessation of leaf expansion while leaf initiation in the apical bud recommences. The apical bud appears dormant during both stages III and IV. Leaf primordia initiated during stage IV expand to form the new shoot during stages I to III. The newly expanded leaves are harvested, forming the green tea crop. Photosynthetic capacity and the pattern of carbohydrate partitioning vary during shoot growth, as defined by the stages of development. Net photosynthesis of mature, fully expanded leaves was highest (18.0 ;C;mol C0₂ m^–2s^–1) during stage I, at the beginning shoot growth and lowest (13.2 μmol C0₂ m^–2s^–1) during stage III, at the cessation of shoot extension. Maximum starch reserves in leaves and internodes of 12.5% (dw) and 22% respectively were reached at the cessation of shoot extension, during stage III, and declined significantly to 0% and 9% respectively at the start of shoot growth during stage I. At the start of shoot growth, the major part of ¹⁴C label was partitioned to the bud, with the developing leaf primordia assumed to be the major sink organs as leaf initiation had ceased. Changes in sink activity with ontogeny are linked to changes in both photosynthesis and partitioning of assimilates during shoot growth and culminate in rhythmic growth of tea.     

桃品种耐寒性研究

用电导法、萌芽生长法和组织变褐法对82个桃品种或优系的耐寒性评价,结果表明：桃一年生休眠枝的耐寒温度为-19．0～-27．0℃,叶芽为-18．5～-26．1℃,花芽为-17．0～-24．0℃;枝、叶芽和花芽三者间耐寒性呈显著正相关,抗性强弱的顺序为：枝＞叶芽＞花芽;枝组织的耐寒力顺序为：韧皮部＞木质部＞形成层＞髓;品种间、品种群间及变种间抗寒性也有不同程度的差异。提出在很少发生-23．0℃以下低温的地区为桃适宜经济栽培区。     

“桂橙一号”的遗传鉴定

＂桂橙一号＂成熟果实风味浓郁,为探明＂桂橙一号＂的亲本,本研究应用倍性检测、形态学标记和AFLP、SSAP等分子标记对其进行遗传鉴定。倍性检测证实＂桂橙一号＂为二倍体。形态学观察表明,其叶形指数、气孔密度、气孔纵径与冰糖橙的差异显著,叶形比冰糖橙更接近椭圆,气孔密度更高。SSAP标记显示,＂桂橙一号＂与冰糖橙相比存在1个多态性位点。通过对差异片段的回收、测序及序列比对结果表明：该差异片段长102bp,与柑桔抗CTV基因同源性高达87%。表明＂桂橙一号＂是不同于冰糖橙的芽变新种质,可以直接作为品种资源加以利用。     

大白菜DH群体TuMV抗性的QTL定位与分析

 利用已构建的包含287个标记位点的遗传图谱的大白菜DH群体,采用多模型QTL作图的方法,通过苗期人工接种TuMV-C₄株系对来自抗病亲本Y195 93和感病亲本Y177-12的DH群体的TuMV抗性进行QTL分析。共检测到3个QTLs,分别位于R03、R04和R06连锁群上,解释的表型变异在10.5%~21.9%之间,3个QTLs可解释40.0％的表型总变异。其中位于R04上命名为Tu-2的QTL解释的表型变异最高,为21.9%,其余两个位于R03和R06上的QTLs,分别解释10.5%和14.5%的表型变异。     

用于白菜和大白菜品种鉴定的EST-SSR复合标记的建立

 为了有效和全面鉴定白菜和大白菜品种, 研制了由3个引物对组成的6套EST-SSR复合标记 组合, 并形成了多重SSR的最佳实用试验条件。经由这6套标记组合完全鉴别了43个白菜和大白菜品种差异的检测, 并在3个大白菜杂交种个体之间的表现一致, 比较了单引物标记与复合标记的鉴定效率, 验证了这套技术和组合可以表达白菜和大白菜品种间多态性、品种内一致性及稳定性和重复性, 确认其可以高效准确和全面地鉴别白菜和大白菜品种的真实性和杂交种纯度。     

国外芋杂交技术研究进展

对国外芋品种杂交技术、育种、遗传分析等方面进行综述,并对今后芋杂交方面存在的问题进行了讨论。     

In vitro regeneration and genetic transformation of common bean (Phaseolus vulgaris L.)—Problems and progress

Common bean is one of the most cultivated species in the Leguminosae family. Thus far, progress in bean improvement has been achieved mainly by conventional breeding methods. These methods, however, in addition of being time-consuming and labor-intensive, are met with a wide range of problems including traits associated with low genetic variation, low survivability of interspecific hybrids, specific inheritance of some valuable characteristics such as yield, disease, and pest resistance, as well as harvesting characteristics. Plant biotechnology offers different strategies to overcome these difficulties. With some exceptions, species belonging to the Leguminosae are difficult to regenerate in vitro. In this review, we discuss the potential and limitations of in vitro cultivation of Phaseolus vulgaris L. based on the existing literature data. Different tissue culture methods like somatic regeneration are discussed and evaluated as well as gene transfer and other approaches in bean modification in vitro.     

小菘菜游离小孢子培养技术研究

以4个引自日本的小菘菜杂交种为试材进行小孢子培养,对影响小菘菜胚状体发生及其成苗的因素进行分析。结果表明：通过游离小孢子培养,获得了大量的小孢子胚状体及再生植株85株;不同基因型间的小孢子胚诱导率差异显著;4 ℃低温预处理24 h对小孢子胚的发生具有促进作用;NLN-13+0.2 mg?L-1 6-BA+0.1 mg?L-1 NAA为适宜的诱胚培养基;50 r?min-1低频振荡培养有利于提高子叶形胚发生的比例;MS+3 %蔗糖+0.75 %琼脂+0.1 g?L-1活性炭是小孢子植株继代和壮苗的适宜培养基;MS+3 %蔗糖+ 0.75 %琼脂+0.1 mg?L-1 NAA是小孢子植株适宜的生根培养基。     

The first intraspecific genetic linkage maps of wintersweet [Chimonanthus praecox (L.) Link] based on AFLP and ISSR markers

Wintersweet [Chimonanthus praecox (L.) Link] (n = 11), a dichogamous species, is a famous traditional fragrant flower plant in China. We used AFLPs and ISSR to construct a genetic linkage map on a pseudo-F₂ population of wintersweet derived from a cross between the individuals H4 and H29. A total of 370 polymorphism markers was generated from 12 AFLP primer combinations and 9 ISSR primers. Two separate female and male maps were constructed using 84 female-specific and 51 male-specific testcross markers, respectively. The maternal H4 map included 80 markers ordered in 12 linkage groups; while the paternal H29 map had 47 markers in 8 linkage groups. At a minimum logarithm of the odds (LOD) score of 3.0 and maximum map distance of 50 cM, the female map covered 2417.8 cM, with an average distance of 25.61 cM and maximum map distance of 48.2 cM between two loci. In contrast, the male map covered 1184.2 cM, with an average distance of 25.7 cM and maximum map distance of 49.0 cM between two loci. These genetic maps will serve as a framework for mapping QTLs and provide basic information for future molecular breeding studies.     

普通白菜苗期耐热性鉴定方法研究

采用人工气候箱高温处理方法,分别于春、秋和夏季,在6种不同的高温条件下对10份普通白菜材料进行连续7 d的高温处理研究其耐热性.结果表明,在不同的高温胁迫下,各供试材料均会出现不同程度的热害症状,如叶片反卷、失绿等,并随着温度的升高和处理时间的延长,热害症状加剧.以春季和秋季采用37 ℃/27 ℃(昼,夜)处理幼苗4 d后调查其热害指数,可以显著反映出普通白菜各品种间的耐热性差异.而夏季采用自然温度育苗后在37 ℃/27 ℃(昼,夜)下不能显著区分普通白菜各品种间耐热性差异.     

平邑甜茶×扎矮山定子杂交后代的胚胎发育特征研究

 利用激光扫描共聚焦显微镜（LSCM）和石蜡切片技术对平邑甜茶与扎矮山定子杂交获得的6个皱叶矮生型株系的胚胎发育过程及发育特性进行了观察与研究。结果表明：各皱叶矮生型株系在胚胎发育过程中表现出的特征大体相同,能进行正常的减数分裂并由功能性大孢子形成的有性胚囊表现出良好的发育趋势;在开花当天至花后2 d,各株系的胚囊中均出现了精核或花粉内容物,观察到了部分株系的受精卵;在花后10 d左右原胚形成。另外,在胚囊发育的特定时期,胚囊内细胞核的分布方式各株系间略有差异;在部分株系中观察到了少数多胚囊现象。综合而言,皱叶矮生型株系的胚胎发育特征是以有性生殖为主要的生殖方式,与亲本扎矮山定子的胚胎发育特征较为一致;而与亲本平邑甜茶不同,未出现平邑甜茶胚胎发育中的复杂现象并表现出较低的无融合生殖能力。     

大白菜种子人工老化及劣变的生理生化分析

研究了大白菜种子人工老化过程中所发生的一系列生理生化变化。结果表明：随着种子老化加深,种子活力指数、ＰＯＤ、ＳＯＤ、脱氢酶、酸性磷酸酶、脂肪酶活性逐渐降低,ＭＤＡ及芥子碱含量逐渐增加,且品种间有差异。认为大白菜种子人工老化及劣变的主要机制在于膜过氧化作用加剧。