Kataoka R, Hara M, Kato S, Isobe S, Sato S, Tabata S, Ohmido N
Graduate School of Human Development and Environment, Kobe University, Kobe, Japan.
Cytogenet Genome Res. 2012;137(1):60-9. doi: 10.1159/000339509. Epub 2012 Jul 11.
Red clover (Trifolium pratense L.) is a forage legume and an allogamous diploid plant (2n = 14; 440 Mb). Here, we examine the 7 prometaphase chromosomes of red clover using fluorescence in situ hybridization (FISH) with ribosomal RNA sequences, pericentromeric and telomeric repeats, as well as bacterial artificial chromosome (BAC) clones. Position of hybridization signals and chromosome condensation patterns were quantified by the help of the chromosome image analysis system ver. 4.0 (CHIAS IV). Fourteen BAC clones belonging to linkage groups (LG) 1-7 hybridized to individual chromosomes 4, 2, 6, 5, 1, 7, and 3, respectively. Quantitative analysis of FISH mapping and chromosome analysis using CHIAS IV allowed us to construct a quantitative idiogram that constitutes the comprehensive chromosome map of red clover. Chromosomal positions of the 26S rDNA locus were detected at a heterozygous locus on chromosome 6 in the variety HR, and polymorphisms of rDNA loci were observed in other varieties, although chromosomal positions of some BAC clones did not vary among HR and other varieties. These results demonstrate chromosomal collinearity among allogamous red clover varieties. This integration of genetic linkage and quantitative chromosome maps should provide valuable insight into allogamous legume genetics.
红三叶草（Trifolium pratense L.）是一种豆科牧草，是一种异花授粉的二倍体植物（2n = 14；440 Mb）。在这里，我们使用核糖体RNA序列、着丝粒和端粒重复序列以及细菌人工染色体（BAC）克隆，通过荧光原位杂交（FISH）对红三叶草的7条前中期染色体进行了研究。借助染色体图像分析系统ver. 4.0（CHIAS IV）对杂交信号的位置和染色体凝聚模式进行了量化。属于连锁群（LG）1-7的14个BAC克隆分别与第4、2、6、5、1、7和3号染色体杂交。利用CHIAS IV对FISH图谱进行定量分析和染色体分析，使我们能够构建一个定量核型图，该图构成了红三叶草的综合染色体图谱。在HR品种的第6号染色体上的一个杂合位点检测到了26S rDNA基因座的染色体位置，在其他品种中观察到了rDNA基因座的多态性，尽管一些BAC克隆的染色体位置在HR和其他品种之间没有变化。这些结果证明了异花授粉红三叶草品种之间的染色体共线性。这种遗传连锁和定量染色体图谱的整合应该为异花授粉豆科植物遗传学提供有价值的见解。
