中国葱属单生组4种植物的核型研究

Karyotypes of 4 species in Allium sect. Haplostemon Boiss. from China

对葱属单生组Alliumsect.HaplostemonBoiss.的 4种 8个地方居群的核型进行了研究 ,其中 3个种的核型属首次报道。研究结果表明 :除在棱叶韭内同时具二倍体、三倍体和四倍体居群外 ,所研究的其余种的居群均为二倍体。以本研究为基础 ,结合国内外对该组已有的细胞学研究 ,得出以下结论 :( 1 )单生组的染色体基数为 8,在组内存在 1A和 2A两种核型类型 ;( 2 )组内随体染色体类型丰富 ,在该组物种的生存适应方面可能起重要作用 ;( 3)有些种 (如薤白A .macrostemon、棱叶韭A .caeruleum等 )表现出明显的种内核型分化 ,有的种甚至在外部形态上也有分化 ;( 4 )高度不育的三倍体 (棱叶韭 )和五倍体 (薤白 )居群靠小鳞茎和珠芽进行无性繁殖 ,以此保持居群的稳定和扩大。另外 ,从生境、繁育制度、多倍化以及这三者之间的关系等方面分析 ,认为在单生组中不同的生境有利于诱发染色体的结构和数目变异 ;多倍化和兼性无融合生殖繁育制度并存 ,则有利于克服染色体变异所带来的育性降低这一繁育障碍 ,同时使居群中所发生的染色体变异得以保存。因此 ,多倍化和兼性无融合生殖繁育制度并存是该组中多倍体类群进化的重要机制之一。

Karyotypes of eight populations representing four species of the genus Allium were analyzed. Included in this study are first reports of the karyotypes for three species from China. All species examined were diploids, except Allium caeruleum in which diploid, triploid and tetraploid were found. The results of this study and chromosome data previously published show that: 1) the basic chromosome number of sect. Haplostemon is x=8, and the karyotypes of all the species in this section belong to Stebbins' 1A and 2A types; 2) polymorphism in satellited chromosomes among different populations of the same and different species may play an important role in the adaptability of the plants to the habitats; 3) some species of this section, such as Allium caeruleum and A. macrostemon , appear to be karyotypically diverse at the infraspecific level, and some species show intraspecific morphological variation and 4) the sterile triploid A. caeruleum and the sterile pentaploid A. macrostemon increase population size vegetatively through multiplication of bulbs and bulbils. The relationship of their habitats, breeding systems and polyploid in the section are discussed. Vegetative reproduction and polyploidy are important in the evolution of polyploid species of sect. Haplostemon.