披碱草属与大麦属系统关系的研究

A STUDY ON SYSTEMATIC RELATIONSHIPS BETWEEN ELYMUS AND HORDEUM (POACEAE)

禾本科中,披碱草属Elymus L.为多倍体属,约含150余种;大麦禹Hordeum L.具倍体和多倍体,约有40余种,该两属均广泛地分布于全球温带地区。该两属,尤其是被碱草属的系统分类较为困难。基于形态学的传统研究认为这两个属的系统关系较远,而细胞学研究的资料却表明,披碱草属的H染色体组起源于大麦属。笔者对来源不同的披碱草属和大麦属的物种进行了远缘杂交,并对其属间杂种F_1的减数分裂中期I染色体配对行为进行了分析。结果表明,若以披碱草属作母本,该两属有相对较高的杂交亲合力,通过对杂种幼胚进行分割和离体培养,也能获得杂种F_1植株。属间杂种植株的形态介于双亲之间,但更接近于披碱草属,杂种的生殖器官发育不健全,而且所有的杂种F_1均完全不育。细胞学的观察结果表明,这两个属间的杂种F_1通常具有较低的减数分裂中期I染色体配对数,但有较大的变异。通过笔者的工作及掌握的形态学和细胞学的资料分析认为:披碱草属和大麦属的亲缘关系较为复杂,不能一概而论。含H染色体组的披碱草属和大麦属物种有着较近的亲缘关系,但这两个属中所含的H染色体组已产生了程度不同的分化;不含H染色体组的披碱草属及大麦属的物种具有较远的亲缘关系。

Elymus L. and Hordeum L. are the two largest genera in the wheat tribe (Trit-iceae Dum. ). The former comprises approximately 150 perennial and exclusively polyploid species and the latter encompasses about 40 perennial or annual taxa with different ploidy levels. Both of the genera are widely distributed in the temperate regions all over the world. Owing to the fact of a large number of species in each genus, wide geographic distribution, various ecological habitats, and a great variation in morphology between and within species, the taxonomy at species level in the two genera, particularly in the genus Elymus, becomes extremely difficult. Based mainly on the morphological studies, the traditional taxonomists concluded that the two genera possessed comparatively distant biosystematic relationships. However, the data based on the cytological studies have shown that the H genome in Elymus has its origin from species in Hordeum . In order to shed light on the biosystematic relationships between the two genera, the present author conducted intergeneric hybridization between species in Elymus and Hordeum with different origins. Chromosome pairing behavior was observed and analyzed at metaphase I of meiosis in the parental species and their inter-generic hybrids. It was shown from the present study that comparatively high crossability occurred between species in the two genera when Elymus species were used as female, and that the hybrid plants could be easily obtained with the add of embryo culture techniques. The morphology of the intergeneric hybrids, which were generally weaker and smaller than the parents, was intermediate between the two parents, but more closely resembled that of the female parents, i.e., Elymus.. The reproductive organs of the intergeneric hybrids developed incompletely in some hybrid combinations and abnormally in all hybrids with non-dehiscent anthers. All the hybrid plants were completely sterile. The results from cytological observation showed relatively low chromosome pairing at metaphase J of all the F| hybrids, albeit with a large variation between different combinations. It is concluded from the present experimental data together with some other morphological and cytological observations obtained previously that the biosystematic relationships between the two genera Elytnus and Hordeum is very complicated and can not be generalized in a simple way. Species which share the H genome in the two genera have comparatively close biosystematic relationships, but the H genomes in different species of the two genera have more or less differentiated during the evolutionary process. Species which do not contain the H genome in the two genera have rather distant phylogenetic relationships.