FISH analysis of intraspecific aneuploids in Carex blepharicarpa

种内非整倍体存在于苔草属的许多物种中。非整倍体被认为很容易通过染色体分裂或融合而产生，因为所有物种的苔草都扩散了着丝粒染色体。报道了一条连续的染色体数目，2n=26~32。本研究分析了采自日本21个种群的灯盏花种内非整倍体的减数分裂构型，并用荧光原位杂交(FISH)技术对18S rDNA进行了染色体定位。种内非整倍体的减数分裂染色体构型在减数分裂中期I，发现了7种种内非整倍体，2n=26~32，几乎所有个体都观察到1~3个异形链三价体。由大、中、小染色体组成的异型三价体普遍存在。在2n=41、46和的三个个体中发现了同型三价体，它们被认为是由未减少配子引起的染色体复制所致。异形三价体在该物种中的高频率表明，大多数非整倍体可能是染色体分裂和/或融合的结果。种内非整倍体的FISH分析将18S rDNA杂交到两个大的和两个中等的二价体的末端。但是，三价体和单价体染色体没有18S rDNA信号。这些结果表明，不含18S rRNA基因的百合非整倍体可能是通过三价体或单价体的不均匀分裂维持在种群内的。

The intraspecific aneuploids are found in many species of the genus Carex. The aneuploids were thought to arise easily by chromosome fission or fusion, because all species of Carex have diffused centromeric chromosomes. A consecutive chromosome numbers, 2n=26～32 are reported in C. blepharicarpa. In this study, meiotic configurations of intraspecific aneuploids of C. blepharicarpa collected from 21 populations in Japan were analyzed, and chromosomal localization of 18S rDNA were determined by fluorescent in situ hybridization (FISH).1. Meiotic chromosome configurations of intraspecific aneuploidsAt meiotic metaphase I, seven kinds of intraspecific aneuploids, 2n=26～32 were found, and one to three heteromorphic chain trivalents were observed in almost all individuals. Heteromorphic trivalents comprising large, medium and small chromosomes were prevalent. Homomorhpic trivalents, which are thought to be originated from chromosome duplications caused by unreduced gametes, were found in three individuals with 2n=41,46, and 64. The high frequency of heteromorphic trivalents in this species indicates that most aneuploidy probably results from fission and/or fusion of chromosomes.2. FISH analysis of intraspecific aneuploidsThe 18S rDNA was hybridized to the terminal regions of two large and two medium bivalents. But, trivalent and univalent chromosomes had no 18S rDNA signal. These results show that the aneuploids of C. blepharicarpa probably maintained within population by unequal divisions of trivalents or univalents with no 18S rRNA gene.