葱属薤白的核型分化

Karyotypic differentiation in Allium macrostemon Bunge

对薤白ＡｌｉｕｍｍａｃｒｏｓｔｅｍｏｎＢｕｎｇｅ的１３个地方居群进行了核型研究，结果表明，１２个国内居群都为四倍体，２ｎ＝４ｘ＝３２；一个日本居群为五倍体，２ｎ＝５ｘ＝４０。１３个居群的核型类型均属Ｓｔｅｂｂｉｎｓ的２Ａ型。薤白种内存在着核型多态性。种内的核型分化与染色体的结构变异有关。主要表现为臂间倒位、罗伯逊易位和或不等相互易位。染色体的结构变异结果导至薤白种内发生明显的核型分化。在１３个居群中，四倍体居群的核型明显可分为两类。第一类的核型公式为２ｎ＝４ｘ＝３２＝２６ｍ（２ＳＡＴ）＋６ｓｍ（２ＳＡＴ），属于该类的有华山居群、商南居群和长春居群。都江堰居群也属该类，但它的一对ｍ随体染色体为一对ｓｔ随体染色体所代替。另一类的核型公式为２ｎ＝４ｘ＝３２＝２４ｍ（２ＳＡＴ）＋８ｓｍ（２ＳＡＴ），沣峪口居群、大飞水居群、汶川居群、武汉居群和红河居群属于该类。此外，宝兴居群、杭州居群、香山居群也属该类，但它们各有一对染色体发生了结构变异。五倍体日本居群的核型属于第一类型，但有两条ｍ染色体为ｓｍ染色体所代替。最后，对薤白种内核型多态性产生的原因从环境因素，繁育制度和多倍性３个方面进行了分析和讨论。认为不同的生境有利于?

Based on a karyotypic analysis of 13 populations, the karyotypic differentiation in Allium macrostemon Bunge was investigated in this paper. The twelve populations from China were all found to be tetraploids with the chromosome number of 2n=32, while the remaining one from Japan was a pentaploid with 2n=40. In the asymmetry, all the karyotypes belonged to Sebbins′2A type. Obvious karyotypic differentiation among the populations, which was highlighted by chromosomal aberrations, including mainly pericentric inversion and the Robertsonian or unequal reciprocal translocations, was detected. Hence the karyotype of this species was somewhat polymorphic. The karyotypes of the tetraploid populations fell into two types. One was formulated as 2n=4x=32=26m(2sat)+6sm(2sat). The populations from Huashan, Shangnan, Changchun, and Dujiangyan had this type, though in the population from Dujiangyan a pair of median satellited chromosomes was found to have changed into subterminal ones. The other was formulated as 2n=4x=32=24m(2sat)+8sm(2sat). The populations from Fengyukou, Dafeishui, Wenchuan, Wuhan, Honghe, Baoxing, Hangzhou and Xiangshan all had this type, but in the three populations from Baoxing, Hangzhou and Xiangshan, a pair of chromosomes had undergone structural aberration. Basically the karyotype of the pentaploid population from Japan fell into the first type, though in it a pair of median chromosomes had been replaced by a pair of submedian ones. Factors which may possibly result in the karyotypic polymorphism, including those of environmental conditions, breeding system and polyploidy, were analyzed. We believe that the diversified habitats might have induced the chromosomal structural aberrations, and the facultative apomictic reproduction and polyploidy might help to surmount the obstacle of reduced fertility and thus maintain chromosomal aberrations in populations. An analysis of the modem distribution pattern shows that Japan may be the differentiation center of Allium macrostemon.