无核早熟沙田柚与花粉败育

在无核沙田柚的基础上,得到了一种新的早熟无核沙田柚。成熟期提前了一个月。本文将同时讨论无核化与花粉败育的关系。无核机理涉及诸多问题,比如花粉败育、雌雄配子体的发育、染色体和基因的变化等。花粉败育是无的一个重要性状。     

假单性结实无核葡萄胚败育机理研究

以Flame Seedless、大粒红无核和京可晶3个假单性结实无核葡萄品种为试材,对其胚和胚乳的发育进行了细胞学观察,并初步探索了胚败育机理.结果表明:Flame Seedless、大粒红无核和京可晶3个无核葡萄品种胚乳开始败育的时期分别为花后29、42、34 d,胚开始大量败育的时期分别为花后39、51、45 d;假单性结实无核葡萄胚的败育是由于胚乳败育、胚缺乏营养所致.     

无核葡萄的育种与胚挽救技术的运用

植物的胚挽救技术在无核葡萄的育种研究中发展迅速。利用假单性结实的无核葡萄作母本,无核品种作父本,杂交后在合子胚未败育时,进行胚挽救即可获得杂种实生苗,无核率可达82％．理论上可达100％。还介绍了运用该技术时杂交亲本的选择、胚挽救最佳胚龄的确定及相应的培养基成分、激素等技术方法。     

无核荔枝假种皮发育过程的研究

无核荔枝是荔枝中较为珍贵的品系 ,种子多退化 ,故为无核品系。其胚珠在发育过程中由于胚囊败育而萎缩 ,假种皮发生于珠脊外侧及外珠被外侧 ,由于胚珠中部的表皮及表层下的几层细胞先后脱分化形成分生组织 ,而在以后的发育中经历一个由“中层”假种皮发育到“平台”假种皮的过程 ,当“平台”假种皮形成以后 ,在其外侧边缘形成一个明显的“上翘”假种皮 ;继而 ,把发育缓慢的胚珠和珠柄包埋 ,而形成“无核”。此外 ,在其发育过程中 ,外界温度对其影响较为明显 :扬花期的高温会产生大核、焦核 ,低温则产生无核 ,因此 ,无核荔枝可能是低温敏感型。     

红芒野稻-莲塘早不育系花粉败育过程的细胞形态学观察

本文对于红芒野稻一莲塘早不育系选育过程中五个回交世代的花粉败育过程进行了观察。结果表明:花粉败育发生的时期从造孢组织开始直至单核花粉晚期。这些时期中都出现各种异常现象,使花粉发育不能进入双核期,最后败育。总的说来,五个回交世代中都可观察到导致花粉败育的各种异常现象;但花粉败育主要是在花粉发育的单核晚期。     

无核沙田柚的RAPD研究——无核机理研究(Ⅱ)

选用经筛选的２０个短序列引物（１０ｎｔ）和随机抽取的２个随机长序列引物,对激光诱导产生的无核沙田柚（处理组）及未经激处理的有核沙田柚（对照组）进行了ＲＡＰＤ（随机扩增多态性ＤＮＡ）分析。结果有６个引物扩增出了共２０条多态性片段,从而表明在沙田柚的处理组与对照组之间,存在着ＤＮＡ分子水平上差异,也就量说,已经引起了沙田柚后代基因组的显著变异,且这种诱导所引起的性状改变是可以遗传的。     

稻类雄性不育系的花粉败育途径研究

对水、旱稻５ 个两系不育系和１ 个三系不育系的花粉败育途径的观察发现,野败三系不育系珍汕９７Ａ 和３ 个两系不育系是以核退化为典型特征的花粉败育途径,其败育时期发生在单核晚期。新选育成的旱稻昆植Ｓ－１ 和水稻昆植Ｓ－２两个两系不育系则是以核增生为典型特征的花粉败育途径。对两类花粉败育途径的细胞学特点和不育的稳定性进行了比较分析     

温敏核不育小麦可育花药和败育花药发育观察

对温敏核不育小麦百农不育系（Bainong sterility,BNS）的可育和不育花药结构进行对比观察。在减数分裂期、小孢子早期和小孢子晚期,可育花药与不育花药的结构相同。小孢子分裂形成二胞花粉后,可育花粉中随着大液泡的分解,细胞质内含物增加,其中出现一些颗粒状物质。不育花药中,小孢子也可分裂形成二胞花粉,但营养细胞的大液泡不分解,细胞质也不增加,最终花粉中的细胞质消失,花粉败育。该种温敏核不育小麦的花粉败育时间发生在二胞花粉早期,可能和其大液泡没有适时分解有关。花粉败育时间的确定为进一步深入研究该种雄性不育小麦的败育机制打下了基础。     

白菜细胞核雄性不育两用系的细胞学观察

对白菜细胞核雄性不育两用系进行了花粉母细胞减数分裂和小孢子发育的细胞学观察,实验结果初步表明不育系小孢子败育时期在减数分裂末期Ⅱ这一阶段,败育方式是不能形成四分体,随后小孢子内颗粒状的内含物不断外溢,直至成为一个空壳,药室萎缩,导致花粉败育。     

作物“三系”生物学特征的研究——Ⅲ.几种水稻雄性不育类型的花粉形成与发育的细胞形态、代谢障碍和药隔维管束发育的比较研究

本文对水稻几种雄性不育类型的花粉败育原因进行了比较研究。结果表明,不育类型的花粉败育有着一些共同的机理:在花粉单核期至三核期可见到花药隔维管束的木质部及韧皮部细胞发育较差,维管束鞘细胞发育不良,体积较小,排列紊乱;在单核花粉期至三核花粉期均发生物质代谢障碍,特别在花药部位尤为明显;由于维管束发育不良和花药物质代谢障碍,导致了花粉缺乏营养而败育。败育的主要时期是在单核花粉晚期,这与代谢发生明显障碍的时期是一致的。     

应用柑橘异源四倍体杂种花粉生产瘪籽沙田柚果实

以3个柑橘异源四倍体体细胞杂种(即四倍体粗柠檬与哈姆林甜橙体细胞杂种,简称"HR";酸柚与粗柠檬体细胞杂种,简称"SR";墨西哥来檬与伏令夏甜橙体细胞杂种,简称"KV")为父本,分别与二倍体单胚性沙田柚进行有性杂交,在生产上获得瘪籽沙田柚果实,并对果实品质进行分析(以四季柚花粉亲本为对照)。结果表明:授予柑橘异源四倍体杂种花粉的果实种子败育十分明显,果实瘪籽率达41.4%～96.0%,与对照间的差异极显著(P0.01);但果实单果重、果肉重、果皮重、果皮厚和果形指数与对照间无显著性差异(P0.05);果实可溶性固形物、全糖、Vc和可滴定酸含量与对照也无明显变化,且较适合于瘪籽沙田柚果实生产的体细胞杂种是HR和SR。     

激光诱变产生无核沙田柚的胚胎学研究

采用激光诱变的方法已经成功的培育出无核(少核)沙田柚,我们采用德国产Leica DMLB生物显微镜MPS60照相系统对采摘回的花蕊(经生物技术处理)进行拍照,与未经激光处理的对照组做比较,分析了雌雄配子体发育过程,对无核果作用机理研究提供参考。     

激光诱变无核沙田柚的染色体研究

选摘经激光诱变得到的第二代无核(少核)沙田柚叶片,和未经激光处理的对照组进行染色体的对比分析,实验分析发现染色体数目发生了改变,出现了非整倍体。本文对染色体数目进行了统计分析,并讨论了非整倍体与无核化之间的关系。     

激光诱变无核沙田柚研究

该研究采用多种激光波长，以不同的功率密度和辐照时间，照射沙田柚枝条的芽点，然后在砍去树冠的７—１０龄树上进行嫁接。先后共辐照１５，０００多个芽点，嫁接在３２０棵树上。实验同时在三个小气候的地质背景略有不同的三个实验基地进行。经过五年多的工作，第一代无核沙田柚已经专家认定，第二代的套袋的无核果亦已得到。过氧化物同工酶（ＰＯＤ）和酯酶同工酶（ＥＳＴ）分析表明：激光处理所出现的谱带均比对照（ＣＫ）多，不同激光波长均有各自的酶谱；进行复合激光处理所得酶谱表现为互补重合。无核果实测确认，风味品质不亚于原来的沙田柚。该研究是成功的。     

Gibberellic acid impairs fertilization in Clementine mandarin under cross-pollination conditions

We investigated the effect of gibberellic acid (GA₃) in the fertilization of Clementine mandarin cv. ‘Clemenules’ (Citrus clementina Hort. ex Tan.), a parthenocarpic variety that produces seedless fruit due to its self-incompatible nature, but yields seedy fruits when grown under cross-pollination conditions.Experiments were conducted with on-tree ‘Clemenules’ flowers and ‘Fortune’ mandarin pollen (C. clementina Hort. ex Tan. × C. reticulata Blanco), which is sexually compatible with the former. Preanthesis treatment at −2 days after anthesis (−2 DAA) enhanced ovule abortion in both unpollinated and cross-pollinated (at +2 DAA) flowers. In the latter, the number of pollen tubes reaching the ovules was significantly reduced although pollen grains were not treated; thus, fertilization was partially avoided and seed set was reduced. When GA₃ was applied at anthesis (0 DAA) at the time of pollination, ovule abortion was again enhanced, and pollen tube growth was completely arrested; thus, fertilization was prevented and seed set was impeded. When GA₃ was applied 24 h after pollination (+1 DAA in flowers pollinated at anthesis), pollen tube growth was impaired but not arrested and ovule abortion was enhanced; therefore, fertilization was not prevented but impaired.We conclude that, when applied the days around anthesis, GA₃ (10 mg l⁻¹) impairs fertilization by either enhancing ovule abortion or reducing pollen tube growth, in ‘Clemenules’ flowers under cross-pollination conditions. The intensity of the response depends on the physiological flower state at the moment of treatment.     

Parthenocarpy of watermelon cultivars induced by γ-irradiation

We found that diploid seedless watermelon can be produced by pollination with partially functional pollen, which was irradiated with γ-rays at the doses of 600 and 800 Gy. The diploid seedless fruits were almost similar to normal fruits in development from pollination to maturity. The number of empty seeds in the diploid seedless fruits varied among the cultivars used. Seedless watermelon cultivars revealed a significant increase in total sugar and carotenoids (lycopene and gb-carotene) contents. The pollen tubes of the pollen subjected to γ-radiation penetrated normally into the synergid, and sperm cells were discharged. Subsequently, the egg nucleus and sperm nucleus became attached to each other in the egg cell and a globular embryo was formed. However, the embryo failed to differentiate the tissues and degenerated. It is suggested that seedless watermelon fruits induced by γ-rays are characterized by increasing yield and better quality due to higher carotenoid and total sugar contents and fruit weight. In some cultivars, there is a tendency in decreasing the thickness of rind.     

Fruit abortion in the Chihuahuan-Desert endemic cactus <Emphasis Type="Italic">Opuntia microdasys</Emphasis>

Resource and pollen limitation, as well as pollen/ovule incompatibility, have been proposed as causes to explain fruit abortion. To assess whether abortion in Opuntia microdasys was due to resource and/or pollen limitation and could therefore be reversed fruit set and seed set were studied using controlled pollination experiments on 60 plants that had been randomly assigned a combination of watering and fertilization treatments. On the other hand, to test whether fruit abortion was irreversible, due to pollen/ovule incompatibility, we examined the reproductive biology of the species. This included observations on floral phenology, nectar production, flower visitors, numbers of pollen grains and ovules, and self-pollination experiments. Results showed that O. microdasys is a fully self-incompatible species and its floral biology and the activity of the main pollinator allow constant deposition of incompatible pollen onto stigmas, which may contribute to fruit abortion. Reproductive success was limited by nutrients and pollen, but the fruit set increased only by 58%, compared to 47% of the control, after the experimental addition of pollen, nutrients and water. The magnitude of pollen and resource limitation suggests that similar levels of abortion will be present in good as well as in bad years. Selfing as well as incompatibility between ramets from the same clone and between closely related plants seem plausible candidates to explain the large proportion of fruit abortion, and experimental cross pollination between genotypes identified through molecular markers are necessary to fully understand the considerable abortion rate that remains unexplained after pollen and resource addition. Interestingly, the possible reason why the abortion of energetically expensive fruits has not been eliminated by natural selection is that the aborted fruits are propagules able to root and produce new plants with the same genotype of the mother. Abortion would have a dramatic effect on cross-fertilized genotypes because they result in zero fitness, but it would have a positive effect on the fitness of the maternal genotype because a clonal offspring is produced. Evidently, the exact fitness consequences to the maternal plant will depend on the differences in survival and reproduction of these different offspring types.     

葡萄胚胎发育与败育过程中胚珠的多胺含量变化

花后40~60d期间,种子败育型无核葡萄胚珠的3种多胺含量明显低于有核葡萄,据此认为无核葡萄胚珠中多胺含量急剧下降和较低的多胺水平可能是导致葡萄胚胎败育的重要原因。(Spd Spm)/Put和Spm/PAs比值变化与葡萄胚胎发育密切相关,较低的比值不利于胚胎的正常分化。