FISH and gene analysis on the origin of high basic chromosome numbers of pteridophytes

用荧光原位杂交(FISH)方法分析了蕨类植物高碱基染色体数目的来源。本文报道了紫薇属三种植物的染色体数目。Ex Murray和O.bank siifolia(Pr.)Kuhn，2n=44，它们的核型非常相似。FISH检测到8个18 S的核糖体基因座位于日本野生稻和普通野生稻的中期培养皿中。然而，在班氏野生稻中，检测到两个基因座。为了获得其他二倍体物种，我们测定了鳞毛蕨科(鳞毛蕨科)23个分类群、鳞毛蕨科(鳞毛蕨科)44个分类群和木兰科(木犀科)54个分类群的体细胞染色体数目。在所研究的121个分类群中，鳞毛虫属12个，蜘蛛纲27个，双倍体13个。FISH在二倍体种Diplazium wichurae(Mett.)的每个中期平板上发现6~8个S rDNA基因座。Diels、菊花鳞毛蕨Di.amamianum Tagawa、汉德鳞毛蕨Dryopteris handeliama C.Chr.和花生Arachniodes sporadosora(Koze)Nakaike.这一证据表明，18 S rDNA的重复在蕨类植物中可能是一种多形性特征，同孢蕨类植物的起源应具有较高的染色体数目。

The origin of high basic chromosome numbers of pteridophytes was analysed by a fluorescence in situ hybridization (FISH) method. The chromosome number of three species of Osmunda, O.japonica Thunb., O.lancea Thunb. ex Murray, and O.banksiifolia (Pr.) Kuhn, was 2n=44, and their karyotypes were very similar to each other. FISH revealed eight 18 S ribosomal DNA (rDNA) loci within a metaphase plate of O.japonica and O.lances. In O.banksiifolia, however, two loci were detected. To obtain other diploid species, we determined somatic chromosome numbers of 23 taxa of Dryopteris (Dryopteridaceae), 44 taxa of (Dryopteridaceae), and 54 taxa of Diplazium (Woodsiaceae). Out of 121 taxa examined, 12 of Dryopteris, 27 of Arachniodes, and 13 of Diplazium were diploids. FISH revealed six to eight 18 S rDNA loci within each metaphase plate of diploid species of Diplazium wichurae (Mett.) Diels, Di.amamianum Tagawa, Dryopteris handeliama C.Chr., and Arachniodes sporadosora (Kunze) Nakaike. This evidence suggested that the duplication of 18 S rDNA should be a plesiomorphic character in pteridophytes and exist homosporous ferns should be originated with high chromosome numbers.