异质生境分布的新疆棱叶蒜的遗传分化和生长适应策略

In China, the largest desert region, an important part of desert region of Central Asian, is located in Xinjiang where plant germplasm resources are specially marked. These plant germplasm resources with resistant characters response and adapt to arid and semi-arid climate. More and more researches focus on these endemic plant species. Tien Shan Mountains and Dzungaria-Tien Shan region are the gene pool of the world Allium germplasm resources. The genetic differentiation of the genus Allium presents particular characteristics under such extreme environmental conditions in Xinjiang and the genetic diversity is important aspect in the genetic study of a species. Allium caeruleum Pall. from heterogeneous habitat, a perennial polycarpic geophyte and only distributed in Xinjiang, China, has morphological differentiation, karyotype differentiation and reproductive system differentiation among natural populations. This study use the integrated methods of germplasm resources, population biology, cytogenetic biology, reproductive biology and molecular biology to observe and analyze genetic diversity, polymorphism and polytypism, the chromosome number, ploidy level and type, phenotypic plasticity, individual reproduction strategy, the annual growth rhythm and breeding system. The results will clarify the relationship between genetic differentiation and adaptive strategy, reveal the effect of environmental conditions on the genetic structure and the genetic differentiation pattern, explore elite germplasm, and master the basic rules and requirements for conservation and sustainable development of Allium caeruleum. It has great significance to clarify plant origin and evolution trend under desert environments in Xinjiang. It is the foundation of core collection constructing，germplasm innovating, gene localizing and cloning, and functional analyzing of Allium caeruleum and its wild and domestic relative germplasm. It provides hybrid materials for polyploidy breeding, resistance breeding and new germplasm creation, and guidance for xerophytic utilization and ecological safety under the severe and unpredictable desert conditions in Xinjiang, China.

新疆天山以及准噶尔-天山区域是世界葱属种质资源的基因库，新疆的极端环境使葱属植物资源遗传分化呈现区域特殊性和多样化特征。异质生境分布的棱叶蒜国内仅分布于新疆，该资源存在形态分化、核型分化和繁殖方式分化等问题。本研究运用种群生物学、细胞遗传学、繁殖生物学和分子生物学等综合手段，通过遗传多样性、细胞倍性、性状表型与繁殖行为研究综合分析棱叶蒜的遗传分化和生长适应策略，揭示棱叶蒜遗传结构和分化格局的形成与荒漠环境之间的关系，发掘优异种质，掌握棱叶蒜种质资源保护和可持续利用的基本规律和要求。对阐明荒漠环境下植物起源和适应性进化趋势具有重要意义。为棱叶蒜核心种质建立与近缘种种质创新和基因定位、克隆与功能分析奠定基础，为倍性育种、新种质创建、抗性品种选育提供亲本材料，为新疆葱属资源植物的生态安全、种质资源利用与保护提供指导。

棱叶蒜是国内仅分布于新疆的重要葱属植物，本研究以异质生境分布的棱叶蒜为研究对象，掌握其生物学信息，了解新疆特殊地理环境下棱叶蒜的生殖适应策略，研究结果如下： .（1）棱叶蒜分布在81°09′49″ N - 86°38′14″ N、48°15′35″ E - 43°15′42″ E、海拔320 m - 1896 m的生态区。数量性状和质量性状的遗传多样性指数分别为0.10-1.68和0.10-1.11。45份材料分为5个类群，主成分分析的6个因子累计贡献率为81.88%。 .（2）棱叶蒜存在二倍体、三倍体和四倍体，具有m、sm染色体；具有L、M2、M1以及S相对长度的染色体；核型不对称系数为58.58%~62.70%，核型类型为2A或2B；有随体。染色体组成、结构和进化程度在居群间存在差异，呈现多样性的特点。 .（3）ISSR和SRAP标记的多态性条带所占比例分别为97.38%和96.36%，SRAP标记的有效基因观察数、有效等位基因数、Nei's基因多样性指数以及Shannon信息指数的平均值均高于ISSR标记。.（4）不同倍性棱叶蒜的开花振幅均呈双峰曲线模式，二倍体和四倍体的开花同步指数分别为0.8745和0.8208，表现出大量、集中的开花式样，是能够吸引更多传粉昆虫访问以及应对极端天气的开花式样。温度是棱叶蒜花期重要的环境限制因子，为保障生殖成功，不同倍性棱叶蒜形成了提高生态适应性的特殊开花物候特征。.（5）小花开放历经弹头、张口、吐药、展开、抱合和萎蔫等过程，历时5～7 d。散粉2 h或4 h时的花粉活力最强，可达85.37%，花粉萌发率最高为81.64%。花粉活力和萌发率均在72 h之内，属于短寿命花粉。花丝花柱等长期柱头具有可授性，花丝花柱合拢期至花丝萎蔫期柱头可授性最强。棱叶蒜具有雄蕊先熟、雌雄异熟、雌雄异位以及吸引昆虫避免自交的花部特征。.（6）棱叶蒜的单花花粉量为16180～32130，P/O值为2697～5355；杂交指数OCI为5；棱叶蒜无自发的自花传粉现象，不存在风媒传粉和无融合生殖；三倍体棱叶蒜只能进行无性繁殖，而二倍体和四倍体倾向于异交为主、自交可育，具备兼性异交并需要传粉媒介的混合交配系统的特征，还采取种子休眠、鳞芽无性繁殖的生殖补偿方式保证特殊地理环境下的种群繁衍。