GINOP Sustainable Ecosystems Group, MTA Centre for Ecological Research, Klebersberg Kuno út 3, Tihany, 8237, Hungary.
Department of Botany and Soroksár Botanical Garden, Faculty of Horticultural Science, Szent István University, Budapest, Hungary.
Biol Futur. 2020 Sep;71(3):209-222. doi: 10.1007/s42977-020-00003-x.
Hybridization associated with polyploidization and apomixis is a frequent mechanism of speciation. Sorbus is a genus with ongoing hybridization resulting in a polyploid complex with different parental lineage. Triparens is the smallest hybridogenous subgenus of Sorbus so far known to comprise only two taxa, S. intermedia and S. × liljeforsii that combine the genomes of three taxa (S. aria agg., S. aucuparia and S. torminalis). To elucidate the origins of S. dacica, S. paxiana and S. tauricola, three new trigenomic candidates formerly believed to be of biparental origin with either S. aria agg. × S. aucuparia or S. aria agg. × S. torminalis lineage we combined data from HPLC and chloroplast DNA analysing additional 33 related taxa as well. We concluded that the 'torminalis-type' flavonoid profile and the 'aucuparia-type' plastid indicate the participation of both S. torminalis and S. aucuparia resulting in the formation of S. dacica, S. paxiana and S. tauricola. Sorbus aria agg. as the third ancestor and as a necessary link to meet genes of S. torminalis and S. aucuparia in one genome is obvious from morphological features (densely tomentose undersides of leaves). The tetraploid cytotypes and obligate pseudogamy of S. dacica and S. paxiana were determined by flow cytometry and are published here for the first time. The most probable evolutionary scenario for Triparens species is: 1. a diploid sexual S. aucuparia as pollen acceptor hybridized with a tetraploid apomictic taxon from the S. aria agg. producing a triploid apomictic taxon with 'aucuparia-type' plastid inherited maternally; 2. during a second crossing event this subgenus Soraria hybrid as maternal progenitor hybridized with the sexual diploid S. torminalis (providing gene(s) of apigenin O-glucuronide synthesis) forming a tetraploid Triparens hybrid with 'aucuparia-type' plastid and 'torminalis-type' flavonoids.
杂交与多倍体化和无融合生殖相结合是物种形成的常见机制。苹果属是一个正在发生杂交的属，导致具有不同亲本谱系的多倍体复合体。Triparens 是迄今为止已知的最小的杂种亚属，仅由两个分类群组成，即 S. intermedia 和 S. × liljeforsii，它们结合了三个分类群（S. aria agg.、S. aucuparia 和 S. torminalis）的基因组。为了阐明 S. dacica、S. paxiana 和 S. tauricola 的起源，我们将以前被认为是双亲起源的三个新的三生候选种，与 S. aria agg. × S. aucuparia 或 S. aria agg. × S. torminalis 谱系结合起来，同时还结合了来自 HPLC 和叶绿体 DNA 的数据来分析另外 33 个相关的分类群。我们的结论是，“torminalis 型”类黄酮图谱和“aucuparia 型”质体表明 S. torminalis 和 S. aucuparia 的参与，导致 S. dacica、S. paxiana 和 S. tauricola 的形成。苹果属 S. aria agg. 作为第三个祖先，并且作为在一个基因组中遇到 S. torminalis 和 S. aucuparia 基因的必要环节，从形态特征（叶片下表面密集绒毛）来看是显而易见的。通过流式细胞术确定了 S. dacica 和 S. paxiana 的四倍体细胞型和强制性假配子发生，并在此首次发表。Triparens 物种最可能的进化情景是：1. 作为花粉受体的二倍体有性 S. aucuparia 与来自 S. aria agg. 的四倍体无融合生殖分类群杂交，产生具有母系遗传的“aucuparia 型”质体的三倍体无融合生殖分类群；2. 在第二次杂交事件中，这个亚属 Soraria 杂种作为母本祖先与有性二倍体 S. torminalis 杂交（提供芹糖苷 O-葡萄糖醛酸合成基因），形成具有“aucuparia 型”质体和“torminalis 型”类黄酮的四倍体 Triparens 杂种。
