【作者】 王丽；

【导师】 赵桂仿；

【作者基本信息】 西北大学 ， 植物学， 2005， 博士

【摘要】 华山新麦草(Psathyrostachys huashanica Keng.)属禾本科大麦族新麦草属多年生草本植物,为我国特有种,仅分布于陕西华山。由于新麦草属是小麦属的近缘属,加之华山新麦草具有抗旱、抗寒、早熟等许多优良的生物学特性,颇受植物育种工作者的重视。目前,该种已被列为国家一级重点保护植物和急需保护的农作物野生近缘种。本文试图通过胚胎学和遗传多样性两个方面的研究,为华山新麦草的生殖生物学提供基础资料,同时预测华山新麦草的遗传学命运和生存潜能,揭示其遗传变异规律和分化机制,探索其致濒原因。具体内容包括: 1.华山新麦草的胚胎学研究 本文采用常规石蜡切片法对华山新麦草小孢子发生和雄配子体形成过程、大孢子发生和雌配子体形成过程以及胚和胚乳的发育过程进行了观察。结果表明:(1)小孢子母细胞减数分裂为连续型,四分体为左右对称型,成熟花粉为3—细胞型,与小麦属特征一致;(2)华山新麦草大孢子发生始于孢原细胞,大孢子母细胞减数分裂形成直线型四分体,功能大孢子位于合点端,合点端大孢子发育为蓼型胚囊。成熟胚囊为八核七细胞,卵细胞极性明显,助细胞在极核融合前已退化一个,另一个宿存,宿存助细胞丝状器明显,并保留退化助细胞的痕迹。极核排列方向不定,反足细胞在胚囊发育早期增殖,并液泡化;(3)华山新麦草胚胎发生属紫宛型,顶细胞和基细胞都参与胚体的形成。胚胎发育经过二细胞原胚、多细胞原胚、球形原胚、梨形原胚、分化胚和成熟胚阶段。成熟胚具有胚根、胚芽、盾片、胚芽鞘、胚根鞘、外胚叶等典型禾本科植物成熟胚的结构。胚乳发育类型为核型,包括游离核阶段、细胞化阶段和生长成熟阶段。待大量游离核形成之后才形成细胞壁,紧贴胚囊的一层胚乳细胞最后形成种子的糊粉层,其余的胚乳细胞最后充满淀粉粒。华山新麦草的以上特征与一般禾本科植物如小麦基本相同。此外在华山新麦草中还观察到一些特殊点:1) 花粉败育现象;2) 有双孢原细胞、双胚囊以及双球形原胚的现象;3) 反足细胞解体较早,并且有时候异形;4) 胚乳游离核更多还原

【Abstract】 Psathyrostachys huashanica Keng is a perennial grass and belongs to genus Psathyrostachys in Triticeae. Psathyrostachys distributes in center of middle Asia and Caucasus Mt., while P. huashanica, a species endemic to China, is only located in Mountain Huashan in Shaanxi Province. At present, the populations of this species are decreasing, and reaching the edge of extinction. Due to the distributing limitation and importance as breeding material for germplasm storage, it has been considered as the first class of national protected rare plants. For this reason, the present study is significant in probing plant flora, origin and evolution of Triticeae and crop breeding. The results showed as follows: 1. The embryology of P. huashanicaIn this paper, the microsporogenesis, the megasporogenesis, the male gametophyte development, the female gametophyte development and the development of embryo and endosperm of P. huashanica were observed by means of paraffin. The results are as follows: (1) Microsporal mother cells divide according to successive type, tetrads range symmetrically, pollens get mature at 3-celled stage, these characteristics are in line with that of Triticum. (2) The megasporogenesis in P. huashanica begins with archesporial cell. Successive cytokinesis in the megasporocyte follows meiosis and the megaspore tetrads are linear. Functional megaspore is in the chalaza and the monosporic embryo sac is chenopodiad type. Mature embryo sac has 8 nuclei. Egg cell has obvious polarity. One synergid degenerates before fertilization, and the other does after fertilization. Two polar nuclei array in three ways. The antipodal cells degenerate lately. (3) The formation and development of the embryo and endosperm is in accordance with the typical graminaceous plants. The embryogeny conforms to the Asterad type. The top cell and the base cell take part in the structure of embryo. There are 5 stages during thedevelopment of embryo, including the stage of 2-celled proembryo, multicellular proembryo, globular proembryo, pyriform proembryo, differential embryo and mature embryo. The mature embryo is composed of radicle, coleorhiza, plumule, coleoptile, scutellum and epiblast. That is the typical structure of the mature embryo of grass. The endosperm development follows the Nuclear type and includes three successive stages, which are free endosperm nucleus stage, cellularization stage and nurture stage. The cell wall is formed after the free endosperm nucleus is formed. The outmost layer of endosperm cell differentiates into the aleurone layer, while the other cells are filled with starch grains. It has three features as follows: 1) pollen abortion near two-celled stage is observed; 2) the double archesporial cells, the double embryo sacs and the double spherical original embryo are discovered; 3) the antipodal cell disintegrates earlier; 4) the number of nucleolus is numerous at the stage of free endosperm nucleus and cellularization.2. Genetic structure and differentiation of P. huashanica populations detected with RAPD markersRandomly amplified polymorphic DNA (RAPD) markers were used to analyze genetic structure and differentiation of P. huashanica populations sampled in three valleys (Huangpu, Xian and Huashan valleys) in Mt. Huashan. One hundred and twenty-two RAPD fragments were obtained in all 266 individuals with 20 primers with mean of 6.1 (2~ 10) fragments per primer. The percentage of polymorphic loci (PPB) is 60.66% in Huangpu Valley, 90.98% in Xian Valley, 95.08% in Huashan Valley, and the total PPB is 95.08%, which indicated a highly genetic variability of P. huashanica. The Shannon’s Information index and Gst are 0.3306 and 0.3263, respectively, indicating that there were more genetic variations within the subpopulations than those among the subpopulations. The gene flow among the subpopulations of P. huashanica (Mw=l .0322) is much less than that of the common anemophytes (Nm=5.24). Mean genetic distance is 0.1571 (range: 0.0022 ~ 0.2901). The highest value of genetic distance was found between the subpopulations (hpl) of Huangpu Valley and the highest altitude subpopulations (h8) of Huashan Valley. Correlation analysis detected significant correlation between genetic distance and vertical distance of altitude. Clustering analysis and principal coordinate analysis revealed the genetic differentiation among thepopulations of P. huashanica. Differentiation mainly occurred between the higher altitude subpopulations and the lower altitude subpopulations, suggesting that altitude might be the major factor that restricted the gene flow between different altitude subpopulations and resulted in differentiation of subpopulations. 3. Genetic diversity analysis of the endangered and endemic species P. huashanica natural populations using simple sequence repeats (SSRs) markersThe microsatellites of barley were used to analyze genetic diversity of P. huashanica populations sampled from three valleys (Huangpu, Xian and Huashan valleys) in Mt. Huashan. A total of 33 alleles of 11 loci were detected from 266 individuals. The observed average number of alleles (A) is 2.75; the effective number of alleles (Ae) is 1.67. The percentage of polymorphic loci (PPB) is 58.33% in Huangpu Valley, 75% in Xian Valley, 83.33% in Huashan Valley, and the total PPB is 83.33%. About 77.6% of (Fst=0.324 ) genetic diversity was observed within the subpopulations. Genetic differentiation within the subpopulations was higher than that among the subpopulations. Mean genetic distance is 0.17 (range: 0.010~0.401). Furthermore, this study has found a high level of transferability of SSR markers among related genera in the Gramineae plants.更多还原