関東地方およびその周辺地域におけるシロヨメナ群の倍数体と地理的分布.IV.

In order to make survey of geographical distribution of polyploids in the Aster ageratoides subsp. leiophyllus group in the Kanto District and surrounding area, 33 localities having 233 individuals were studied karyologically. They were collected from 22 localities of the northwestern region and four of the southwestern region of the Chubu District and seven of the western region of the Tohoku District, beyond the Kanto District (Table 1 and Fig. 2). In the 28 localities of the Tohoku District and of the Chubu District closing to the Tohoku District, the tetraploids were confirmed. For the first time four pentaploids were found in Sado Island (12MR). The aneuploids by adition of B-chromosomes varried in number from one to six were found in them. Diploids and hexaploids were also found in two and one localities, respectively. And in the rest two the coexistances with diploids, tetraploids and hexaploids, and with tetraploids and hexploids were found. The polymorphism of the L^<2E>-chromosomes was studied in the tetraploids and the six types were detected. Of the six types, the II 1a was predominant (74.3%) and the II 2a the second highest (21.3%) likewise in the tetraploids studied before. A tetraploid hybrid plant(2n=36=27L+9S) between the tetraploid var. leiophyllus and subsp. ovatus was found for the first time. This might indicate the gene flow between the tetraploid and subsp. ovatus. This is the fourth of a series of paper dealing with the occurrence of polyploids and their geographical distribution of Aster ageratoides subsp. leiophyllus group in the Kanto District and surrounding area (Matsuda and Suyama, 1980; Matsuda and Shinohara, 1985; Matsuda and Shishido, 1988). This study has been extended over the regions which cover a wider range, especially in the Tohoku District and the Chubu District. This report deals with the further results obtained in the 220 individuals belonging to the taxonomic group from the 33 localities situated in the Tohoku District and the Chubu District.関東地方及びその周辺地域において,シロヨメナ群における倍数体の出現とそれらの地理的分布を更に調べるために,中部地方北西部からの22集団,中部地方西部の4集団,そして東北地方西部の7集団から採集した233株を核学的に調べた。その結果,東北地方及び東北地方に近接する中部地方の27集団には,四倍体のみが成育していることが分かった。一方,佐渡島の両津市見立で,四倍体の他に4個体だけであるが,五倍体(2n=45)が初めて見出された。また,四倍体には1～6個のB染色体の付加による異数体が見出され,B染色体の出現は北部域ほど低かった。なお,B染色体には10型が区別され,小形の型であった。また,二倍体が二倍体の高頻度出現が知られている地域と近接する2集団に,また六倍体が関東地方の六倍体出現地に近接する1集団でそれぞれ見出された。なお二倍,四倍及び六倍体の混生集団が初めて1集団見出され,四倍体と六倍体の混生地も1集団,関東地方と中部地方との境界域で見出された。四倍体の集団において,付随体染色体の多形性が調べられ,6型が区別され,前報と同様にII 1a(74.3%)とII2a(21.4%)の出現が顕著であった。ノコンギクとシロヨメナとの雑種は,六倍性シロヨメナとの五倍性雑種(2n=45=36L+9S)と当地域でも初めて四倍性シロヨメナとの四倍性雑種(2n=36=27L+9S; Tara, 1973)も見出され,シロヨメナとノコンギクとの遺伝子の交換が四倍体においても起こっていることが分かった