中国特有珍稀濒危植物四川牡丹的生殖生物学及保护遗传学研究

Paeonia decomposita is an endemic to China. It has great ornamental and medicinal values, and it is ideal material for flower-breeding. Because of the reproductive and developmental obstacle, genetic factors, inbreeding depression, the change of ecological environment and human disturbance, it is threatened and on the verge of extinction, and has been listed as class II national rare and endangered protected plant. At present, systematic studies on reproductive biology and conservation genetics are absent. In the first place, we are going to study the reproductive biology characteristics (including megasporogenesis, microsporogenesis, development of male and female gametophytes, fertilization and early embryonic development, breeding system, mating system, degree of inbreeding depression and pollination biology) in natural populations of P. decomposita. We will reveal the reproductive and developmental characteristics, find the weak links and restrictive factors in the process of reproduction, reveal endangered reasons resulted from abortion, reproductive failure, reproductive obstacle and inbreeding depression, clarify the endangered causes and mechanisms of reproductive biology, and clarify the relationship between reproductive biology characteristics and the endangering. Secondly, we will study the genetic diversity by using molecular markers, calculate the genetic parameters with related software, cluster and analyze the tested individuals and populations, reveal the genetic structure, understand and analyze the mating system and its evolutionary mechanism from the perspective of genetics, clarify the endangered causes and mechanisms in genetics, and clarify the relationship between genetic diversity and the endangering. Thirdly, according to the research results, we will determine the conservation units in priority, and put forward conservation strategy of germplasm resources. This research will provide the scientific basis for the effective conservation, rational development, hybridization breeding and sustainable utilization.

四川牡丹是特有种，有很高的观赏和药用价值，是理想的花卉育种材料。由于生殖发育障碍、遗传因素、近交衰退，再加上环境变化、人为干扰，已受到灭绝威胁，被列为国家二级珍稀濒危保护植物。目前缺少对其生殖生物学和保护遗传学的系统研究。选取四川牡丹自然居群，研究生殖生物学特性(包括大小孢子发生、雌雄配子体发育、受精及早期胚胎发育、繁育系统、交配系统、近交衰退程度及传粉特性)，揭示生殖发育的特点，找到生殖过程中的薄弱环节和限制因素，揭示败育、生殖失败、生殖障碍、近交衰退导致的濒危原因，阐明濒危的生殖生物学原因和机制，弄清与该种濒危的关系。用分子标记研究遗传多样性，计算遗传参数，对供试材料进行聚类分析，揭示遗传结构。从遗传学角度了解和分析交配系统及其进化机制，阐明濒危的遗传学原因和机制，弄清与该种濒危的关系。确定优先保护单元，制定种质资源保护策略。为进行有效保护、合理开发、杂交育种及可持续利用提供科学依据。

四川牡丹是我国特有种，是重要的观赏、药用和食用植物，是理想的花卉育种材料。受生殖障碍、遗传因素、近交衰退、环境变化以及人为干扰等多种因素威胁，四川牡丹已近灭绝，被列为濒危植物，但目前缺少对综合因素的系统研究，其濒危机制不清楚，保护策略不明确。.对四川牡丹进行了野外调查，研究了生殖特性、遗传多样性和遗传结构。结果发现：四川牡丹不能进行无融合生殖和风媒传粉，交配系统属异交，部分自交亲和，需要传粉者。结籽率的近交衰退强度最高(0.78)，累积值(0.9497)为正值，异交后代的适应性表现优于自交后代。所有被研究的个体均为染色体倒位杂合子，倒位的多样性高，表明倒位的来源不同，且发生频率较高。花粉母细胞减数分裂异常、遗传多样性中等偏低、干旱和极端天气、传粉限制、传粉者限制、心皮空间限制等因素，导致结籽率降低。结籽率较低是四川牡丹濒危的主要原因之一。.四川牡丹居群分布零星，范围狭窄，规模小，居群间空间距离远，限制了居群间的传粉和基因流，导致自交和近交，遗传多样性下降到He=0.405，低于特有种(He=0.420)和广布种(He=0.620)。丹巴居群被确定为遗传多样性中心。Mantel检验表明居群间的地理距离和遗传距离呈正相关(r=0.592，P=0.0001)，符合距离-隔离(IBD)模型。AMOVA分析表明遗传变异主要存在于居群内(73.48%)，而不是居群间(26.52%)。UPGMA聚类树将11个居群分为两个遗传组，准确反映了居群间和居群内的遗传关系。结构分析和主坐标分析(PCoA)将11个居群分为3个遗传组，并支持UPGMA聚类结果。丹巴、金川、马尔康三个自然分布区对应三个保护管理单元。建议通过建立小型自然保护区、提高栽培规模和育种技术，进行就地保护、迁地保护和自然回归保护。.通过本研究，我们分析了四川牡丹的交配系统及其进化意义，揭示了近交衰退程度及其对居群生存力的影响，阐明了居群间的迁移和进化关系，探明了濒危的生殖和遗传机制，并制定了科学合理的保护策略。本研究为今后珍稀濒危植物种质资源的保护、管理和改良提供了科学依据，为合理开发、可持续利用及亲本选育提供了参考。

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