Analysis of Breeding Systems, Ploidy, and the Role of Hexaploids in Three Hypericum perforatum L. Populations.
Analysis of Breeding Systems, Ploidy, and the Role of Hexaploids in Three Hypericum perforatum L. Populations.
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三个贯叶金丝桃群体的育种系统、倍性和六倍体的作用分析。
DOI：
10.1016/j.indcrop.2010.01.005
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发表时间：
2010
影响因子：
5.9
通讯作者：
Rigby,ShawnM
中科院分区：
文献类型：
--
作者：
Qu,Luping;Widrlechner,MarkP;Rigby,ShawnM
贯叶连翘的六倍体种子是由四倍体居群产生的，但六倍体幼苗的命运及其繁殖行为尚未得到仔细的研究。本研究利用流式细胞术对三个贯叶连翘材料的单粒种子和单株样品进行了分析，以确定其倍性水平和繁殖途径。3份材料的种子均为兼性无融合生殖，四倍体细胞类型占优势(85-91%)，六倍体频率较低(9-14%)，二倍体仅在一个群体中检测到(5%)。苗木群体由四倍体(87-97%)和六倍体(3-13%)组成。六倍体胚胎很可能是由四倍体的2n配子产生的，并由正常的、减少的四倍体雄性配子受精。这些六倍体预计会产生不平衡的配子，因为它们具有染色体互补，其中包括最初来自两个不同物种的两个三倍体集合。观察到一些四倍体种子的胚乳细胞DNA含量很高，这表明六倍体产生的一些不平衡的雄配子是明显可行的，并可能影响受精。这一机制是否也适用于卵细胞，或者六倍体是否能够产生未退化的胚囊尚不确定。由于严重的繁殖困难，六倍体幼苗在基因流动和进一步进化中可能只起到很小的作用。六倍体在减数分裂中进化为二价体配对频率增加的类型的可能性相对较低。然而，六倍体可能包括新的化学类型，如果能够在其中识别出有价值的药用类型，这些新的化学类型可以无性繁殖。
Hexaploid seeds are produced by predominantly tetraploid populations of Hypericum perforatum, but the fate of hexaploid seedlings and their reproductive behavior have not been closely examined. We used flow cytometry to analyze single seeds and individual plant samples of three accessions of H. perforatum to determine ploidy levels and reproductive pathways. Seed samples of all three accessions were facultative apomicts, with tetraploid cytotype predominant (85–91%) and a lower frequency of hexaploids (9–14%), with diploids (5%) detected in only one population. Seedling populations consisted of tetraploids (87–97%) and hexaploids (3–13%). Hexaploid embryos are most likely generated by a 2n gamete of the tetraploid and fertilized by a normal, reduced tetraploid male gamete. These hexaploids are expected to produce unbalanced gametes because they possess chromosome complements that include two triploid sets originally derived from two different species. The observation that some tetraploid seeds had endosperm with high cellular DNA content indicates that some unbalanced male gametes produced by hexaploids were evidently viable and could effect fertilization. Whether this mechanism is also true for egg cells or whether the hexaploids are capable of producing unreduced embryo sacs is uncertain. Because of severe reproductive difficulties, hexaploid seedlings may play a very minor role in gene flow and the further evolution of H. perforatum. The likelihood that hexaploids will evolve to types with an increased frequency of bivalent paring in meiosis is relatively low. However, hexaploids may include novel chemotypes, which could be vegetatively propagated if valuable, medicinal types can be identified among them.