赖草属5个种的核型与进化

报道了国产赖草属５个种的核型，即大赖草，２ｎ＝４ｘ＝２８＝２４ｍ（２ＳＡＴ）＋４ｓｍ（２ＳＡＴ）；粗穗赖草２ｎ＝４ｘ＝２８＝２２ｍ（２ＳＡＴ）＋４ｓｍ＋２ｓｔ（２ＳＡＴ）；若羌赖草，２ｎ＝４ｘ＝２８＝２０ｍ（４ＳＡＴ）＋６ｓｍ＋２ｓｔ（２ＳＡＴ）；羊草，２ｎ＝４ｘ＝２８＝２２ｍ（４ＳＡＴ）＋２ｓｍ＋４ｓｔ（４ＳＡＴ）；窄颖赖草，２ｎ＝４ｘ＝２８＝２２ｍ（２ＳＡＴ）＋４ｓｍ（２ＳＡＴ）＋２ｓｔ（２Ｓ

Karyotypes and evolution of five species of Leymus Hochst.

The karyotypes of 5 species of Leymus Hochst.are reported in this paper.The karyotype formulae are as follows: L.racemosus (Lam.) Tzvel.,2n=4x=28=24m(2SAT)+4sm(2SAT); L.crassiusculus L.B.Cai,2n=4x=28=22m(2SAT)+4sm+2st(2SAT); L.ruoqiangensis S.L.Lu et Y.H.Wu,2n=4x=28=20m(4SAT)+6sm+2st(2SAT); L.chinensis (Trin.) Tzvel.,2n=4x=28=22m(4SAT)+2sm+4st(4SAT); L.angustus (Trin.) Pilger.,2n=4x=28=22m(2SAT)+4sm(2SAT)+2st(2SAT).Furthermore,according to Stebbins theory of the karyotypic evolution as well as using the method of coding of cladistics,4 significant characters,the ratio of the longest chromosome to the shortest,the arm ratio in mean,the index of the karyotypic asymmetry and the proportion of chromosomes with arm ratio>1.70,were analysed,the evolutional levels of 5 species were also affirmed.And the result of cytological analysis is consistent with the morphological result analysed with the evolutionary trends of external characters.Both of cytological and morphological evidences indicate that the Sect.Leymus of Leymus Hochst.is a relatively primitive section,the Sect.Anisopyrum (Griseb.) Tzvel.a advanced section,and the Sect.Aphanoneuron (Nevski) Tzvel.is between them.