Elucidation of origin of citrus based on information from chromosome analysis

柑桔是世界上最重要的水果作物之一，属于芦花科7个亚科之一的金果树科，但其起源及金果树科种间的系统发育关系尚不清楚。因此，在本研究中，我们进行了染色体分析，以阐明Aurantioideae的系统发育关系和进化。染色体数目分析表明，几乎所有金蝎科物种的染色体均为二倍体（2n=2x=18）。只有2种为四倍体（2n=4x=36）。五葡萄糖属（Glycosmis pentaphylla）是具有二倍体和六倍体（2n=6x=54）细胞的混合倍体。采用色霉素A3 （chromomycin A3， CMA）荧光染色法对金蝇科16属21种染色体的CMA带型进行了表征和比较。根据cma阳性带的数量和位置，将这些染色体分为6种类型；A：两个端粒和一个近端带，B：一个端粒和一个近端带，C：两个端粒B…更多的手，D：一个端粒带，E：没有带，Dst: D型与一个卫星染色体。每个物种都有一到四种类型的染色体和独特的CMA带型。各部落和亚部落的高级属如Merrillia和Feroniella均呈现异染色质（cma阳性带）。一般来说染色体结构丰富。没有富异染色质染色体的Swinglea glutinosa被认为是最原始的染色体构型，可能是厘清Citreae族进化的关键属。利用核糖体RNA基因（rDNA）进行荧光原位杂交（FISH）是研究系统发育的有力工具。因此，从原始到高级的7个属进行了5S rDNA的FISH。在7个属中，6个属检测到2个5S rDNA位点。本西罗斯有6个5S rDNA位点。从这些结果来看，两个似乎是Aurantioideae中5S rDNA位点的基数。5S rDNA位点数量的多样性发生在柑桔真果树分化后。少

Although citrus, belong to Aurantioideae which is one of the seven subfamilies of Rutaceae, is the one of the most important fruit crop in the world, its origin and phylogenic relationships among species in Aurantioideae has been unclarified. Therefore in this study, we conducted chromosome analysis to elucidate the phylogenic relationships and evolution within Aurantioideae.The chromosome number analysis revealed that almost all Aurantioideae species had diploid (2n=2x=18) chromosomes. Only two species were tetraploid (2n=4x=36). Glycosmis pentaphylla was a mixoploid having diploid and hexaploid (2n=6x=54) cells.Fluorochrome staining with chromomycin A3 (CMA) was used to characterize and compare the CMA banding patterns of chromosomes of 21 species from 16 genera of Aurantioideae. These chromosomes were classified into six types based on the number and position of CMA-positive bands ; A : two telomeric and one proximal band, B : one telomeric and one proximal band, C : two telomeric b … More ands, D : one telomeric band, E : without bands, and Dst : type D with a satellite chromosome. Each species possessed one to four types of chromosomes and unique CMA banding patterns. The advanced genera in each tribe and subtribe such as Merrillia and Feroniella showed heterochromatin (CMA-positive bands). rich chromosome configuration in general. Swinglea glutinosa without heterochromatin rich chromosome, which is considered to be the most primitive chromosome configuration, seems to be the key genus for clarifying the evolution of the tribe Citreae.Fluorescent in situ hybridization (FISH) using ribosomal RNA genes (rDNA) is a powerful tool for phylogenic studies. Thus FISH of 5S rDNA was carried out in seven genera from primitive to advanced one. Two 5S rDNA sites were detected in six out of seven genera. Poncirus had six 5S rDNA sites. From these results, two seem to be a base number of 5S rDNA sites in Aurantioideae. Diversity of number of 5S rDNA sites occurred after the true citrus fruit trees were differentiated. Less