Possible pathways of the gene flow inTaraxacum sect.Ruderalia
Possible pathways of the gene flow inTaraxacum sect.Ruderalia
复制标题
蒲公英组基因流动的可能途径
作者：
L. Mártonfiová
在蒲公英属（Taraxacum）杂草组（sect. Ruderalia）中对繁殖行为以及倍性水平之间的基因流途径进行了实验研究。从二倍体 - 多倍体混合的自然种群中采集了二倍体、三倍体和四倍体个体。在不同倍性水平的植株之间进行了136次实验杂交。对这些杂交产生的种子、从单花头以及开放授粉花头（来自栽培植物和野生植物）获得的种子进行了流式细胞术种子筛选（FCSS），以确定后代的倍性水平并推断母本植物的繁殖行为。研究了基因流的三种可能途径：（A）无融合生殖体的花粉使有性生殖体受精，（B）BIII杂种形成，（C）兼性无融合生殖。当二倍体母本植株与三倍体花粉供体进行实验杂交时，产生了二倍体和多倍体后代，然而当用二倍体和三倍体的混合花粉授粉或昆虫授粉时，未发现多倍体。似乎在与二倍体花粉的混合中，三倍体花粉是无效的。四倍体与二倍体母本更容易产生杂种，它们在野生种群中的作用需要进一步研究。三倍体母本，即使是那些具有近规则花粉的，也没有显示出兼性无融合生殖的迹象。BIII杂种存在于三倍体和四倍体的后代中，在四倍体中所占比例相当高（在一些杂交中高达后代的50%）。
Reproductive behaviour and the pathways of gene flow among ploidy levels were studied experimentally inTaraxacum sect.Ruderalia. Diploid, triploid and tetraploid individuals were sampled from mixed diploid — polyploid natural populations. 136 experimental hybridizations between the plants of different ploidy levels were performed. Seeds resulting from these crosses, those obtained from isolated anthodia as well as from open pollinated anthodia (both from cultivated and wild plants) were subjected to the flow-cytometric seed screening (FCSS) to determine ploidy levels in the progeny and to infer breeding behaviour of maternal plants. Three possible pathways of the gene flow were studied: (A) fertilization of sexuals by pollen of apomicts, (B) BIII hybrid formation, (C) facultative apomixis. Diploid maternal plants when experimentally crossed with triploid pollen donors produced diploids and polyploid progeny, while when pollinated with a mixture of the pollen of diploids and triploids or insect pollinated, no polyploids were discovered. It seems that in the mixture with the pollen of diploids, the pollen of triploids is ineffective. Tetraploids produce hybrids much easier with diploid mothers and their role in wild populations requires further study. Triploid mothers, even those with subregular pollen did not show traces of facultative apomixis. BIII hybrids were present in the progeny of both triploids and tetraploids, in tetraploids in quite high percentages (up to 50% of the progeny in some crosses).