一种新的六倍体细胞类型水生薏苡的细胞遗传学鉴定

摘要

通过醋酸洋红压片和荧光原位杂交技术(包括基因组原位杂交技术),确定在我国广西西南部地区广泛分布着的水生薏苡(Coix aquatica Roxb.)属于一种新的六倍体细胞类型.这种水生薏苡与已报道的几种水生薏苡细胞类型的染色体数目均不相同,它的染色体数目是2n=30,在减数分裂前期Ⅰ和中期Ⅰ的细胞中形成10个二价体和10个单价体.基因组原位杂交结果表明,这种水生薏苡的20条染色体与四倍体的薏苡(C.lacryma-jobi,2n＝20)的基因组DNA是高度同源的.45S和5S rDNA分别杂交到这种水生薏苡的两条染色体上,其中各有一条染色体与薏苡中携带45S和5S rDNA杂交信号的染色体具有相同的形状和信号的分布状态.据此推测:四倍体的薏苡可能是这种新的水生薏苡细胞类型的一个亲本,它的另一个亲本可能是八倍体的水生薏苡(C.aquatica,2n＝40),因为这种八倍体的水生薏苡在核型、植株形态及生长环境等方面与新的六倍体细胞类型的水生薏苡相似.%A new Coix aquatica Roxb. cyto-type, found in the southwest of Guangxi Zhuang Autonomous Region in China, was identified and analyzed by acetocarmine squashing and fluorescence in situ hybridization (FISH) technique including genomic in situ hybridization (GISH). This new C. aquatica cyto-type was different from other C. aquatica cyto-types reported in chromosome structure. It was 2n ＝30 in chromosome number, and ten bivalents plus ten univalents were formed in meiotic prophase and metaphase I. GISH results indicated that its 20 chromosomes were highly homologous to chromosomes of allotetraploid species C. lacryma-jobi L. (2n = 20). The 45S and 5S rDNA were respectively located on the two different chromosomes of the C. aquatica. One of chromosomes carrying 45S rDNA showed its chromosome shape and signal location in the C. aquatica as the same as that in C. lacryma-jobi. So did one of chromosomes carrying 5S rDNA. It could be deducted that one of parental candidates for the new C.aquatica cyto-type may be C. lacryma-jobi. The other parental candidate may be allooctopolyploid C. aquatica (2n ＝ 40), which is similar to the new cyto-type of C. aquatica in aquatic habit and plant morphology.