Cytogenetic studies in the genus Zea
Cytogenetic studies in the genus Zea
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DOI：
10.1007/bf00229226
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发表时间：
1991-11
影响因子：
5.4
通讯作者：
C. Tito;L. Poggio;C. Naranjo
中科院分区：
文献类型：
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作者：
C. Tito;L. Poggio;C. Naranjo
在萌发种子根尖的末期核(2C)中，对不同品种和杂种的核DNA含量和异染色质含量进行了分析。结果表明，玉米不同类群、不同品系、不同小种间存在显著差异。杂交种Z。Mayssp.MaysxZ。Maysssp.miciana(2n=20)，Z.diplerennisxZ.Perennis(2n=30)和Z.Perennis(2n=40)的DNA含量介于亲本之间。染色体C-带数目和C-带异染色质所占基因组比例与基因组大小呈正相关。在所研究的不同玉米品系和小种中，基因组大小与萌发到开花的间隔时间呈正相关。八倍体Z。Perennis(2n=40)的每个基本基因组的DNA含量和异染色块最小，表明该物种丢失的DNA主要由重复序列组成。考虑到现存的玉米物种是四倍体(2n=20)和八倍体(2n=40)，而祖先的二倍体已经灭绝，任何关于DNA变化方向(增加或减少)的考虑都是完全推测的。现存的物种可能是在二倍体和/或四倍体水平上对不同的基因类型和核型成分进行自然和人工选择的产物。
The nuclear DNA amount and the heterochromatin content in species and hybrids ofZeawere analyzed in telophase nuclei (2C) of the root apex of germinating seeds. The results revealed significant differences among taxa and also among lines and races of maize. The hybrids betweenZ. maysssp.maysxZ. maysssp.mexicana(2n=20),Z. diploperennisxZ. perennis(2n=30), andZ. diploperennisxZ.perennis(2n=40) showed DNA content intermediate between that of the parents. The number of chromosomal C-bands and the proportion of the genome comprising C-band heterochromatin were positively related to genome size. In the different lines and races of maize studied, there was a positive correlation between genome size and the interval from germination to flowering. OctoploidZ. perennis(2n=40) showed the smallest DNA content per basic genome and the smallest heterochromatic blocks, suggesting that the DNA lost by this species consisted mainly of repetitive sequences. Considering that the extant species ofZeaare tetraploid (2n=20) and octoploid (2n=40) and that the ancestral diploids are extinct, any consideration of the direction (increase or decrease) of the DNA change would be entirely speculative. The extant species could be the product of natural and artificial selection acting on different genotypic and nucleotypical constitutions at the diploid and/or tetraploid levels.