玉米及其近缘种大刍草的核型研究

Karyotypes of Maize and Its Relatives-Teosinte

【目的】对玉蜀黍属现今分类的所有大刍草种和玉米进行染色体核型比较研究,为揭示其进化趋势与种间亲缘关系提供参考。【方法】采用根尖压片法确定玉米和大刍草的染色体数目,并对其核型进行分析。【结果】玉蜀黍属内各个种及亚种染色体数目除四倍体多年生类玉米种为2n=4x=40外,其余种(亚种)的染色体数目均为2n=2x=20。玉蜀黍属内亚属间以及亚属内物种间染色体核型结构差异较小,各个种及亚种染色体均由中部着丝点和近中部着丝点染色体组成,随体全部位于短臂上;除四倍体多年生类玉米种具2对随体外,其余种(亚种)均具1对随体,其中,玉米的随体位于中部着丝点染色体上,大刍草的随体均位于近中部着丝点染色体上。核型分类上,繁茂亚属的4个种均为2A型,玉蜀黍亚属主要属于2B型。【结论】细胞学证据表明,玉蜀黍属除四倍体多年生类玉米种染色体数目为2n=40,其余种(亚种)的染色体数目均为2n=20,玉米和大刍草作为同属的物种,染色体核型结构差异较小;四倍体多年生类玉米种不是由二倍体多年生类玉米种加倍演化而来,它们是2个独立的种。

【Objective】 Karyotypes from maize and teosinte of the current classification of Zea were investigated in order to further reveal the evolution and genetic relationships between species.【Method】 The number of chromosomes in maize and teosintes was calculated by a root tip squashing method,and karyotypes of all species of Zea were analyzed.【Result】 The results were as follows： All the materials are diploids with 2n=2x=20,except Zea perennis（2n=4x=40）.The variation of karyotypes within subsection and species（subspecies） was not observed.The chromosomes of all the materials were metacentric or submetacentric.Except for Zea perennis which had two pairs of satellites,the other species（subspecies） only had one pair,and the satellite was located on the short arm.The satellite of maize was positioned on the metacentric chromosome,while the satellites of teosinte were located on the submetacentric chromosome.The karyotypes of all the taxa in Section Luxuriantes were 2A,while that of Section Zea were 2B type.【Conclusion】 Cytogenetic evidence showed that all the materials of the genus Zea are diploids with 2n=20 chromosomes,except Zea perennis（2n=4x=40）,the difference in variation of karyotypes between maize and teosinte is small,and they are congeneric.Zea perennis is not evolved from the double Zea diploperennis and they are two separate species.