Institute of Botany, Czech Academy of Sciences, Zámek 1, 252 43, Průhonice, Czech Republic.
Department of Botany, Charles University, Benátská 2, 128 01, Prague, Czech Republic.
BMC Plant Biol. 2019 May 31;19(1):230. doi: 10.1186/s12870-019-1806-y.
Interspecific hybridisation resulting in polyploidy is one of the major driving forces in plant evolution. Here, we present data from the molecular cytogenetic analysis of three cytotypes of Elytrigia ×mucronata using sequential fluorescence (5S rDNA, 18S rDNA and pSc119.2 probes) and genomic in situ hybridisation (four genomic probes of diploid taxa, i.e., Aegilops, Dasypyrum, Hordeum and Pseudoroegneria).
The concurrent presence of Hordeum (descended from E. repens) and Dasypyrum + Aegilops (descended from E. intermedia) chromosome sets in all cytotypes of E. ×mucronata confirmed the assumed hybrid origin of the analysed plants. The following different genomic constitutions were observed for E. ×mucronata. Hexaploid plants exhibited three chromosome sets from Pseudoroegneria and one chromosome set each from Aegilops, Hordeum and Dasypyrum. Heptaploid plants harboured the six chromosome sets of the hexaploid plants and an additional Pseudoroegneria chromosome set. Nonaploid cytotypes differed in their genomic constitutions, reflecting different origins through the fusion of reduced and unreduced gametes. The hybridisation patterns of repetitive sequences (5S rDNA, 18S rDNA, and pSc119.2) in E. ×mucronata varied between and within cytotypes. Chromosome alterations that were not identified in the parental species were found in both heptaploid and some nonaploid plants.
The results confirmed that both homoploid hybridisation and heteroploid hybridisation that lead to the coexistence of four different haplomes within single hybrid genomes occur in Elytrigia allopolyploids. The chromosomal alterations observed in both heptaploid and some nonaploid plants indicated that genome restructuring occurs during and/or after the hybrids arose. Moreover, a specific chromosomal translocation detected in one of the nonaploids indicated that it was not a primary hybrid. Therefore, at least some of the hybrids are fertile. Hybridisation in Triticeae allopolyploids clearly and significantly contributes to genomic diversity. Different combinations of parental haplomes coupled with chromosomal alterations may result in the establishment of unique lineages, thus providing raw material for selection.
种间杂交导致的多倍化是植物进化的主要驱动力之一。在这里，我们通过荧光原位杂交（5S rDNA、18S rDNA 和 pSc119.2 探针）和基因组原位杂交（二倍体分类群的四个基因组探针，即 Aegilops、Dasypyrum、Hordeum 和 Pseudoroegneria）对三个 Elytrigia ×mucronata 细胞型进行了分子细胞遗传学分析。
所有 E. ×mucronata 细胞型均同时存在来自 E. repens 的 Hordeum 和来自 E. intermedia 的 Dasypyrum + Aegilops 染色体组，证实了所分析植物的假定杂交起源。E. ×mucronata 的基因组组成如下：六倍体植物表现出三个来自 Pseudoroegneria 的染色体组和一个来自 Aegilops、Hordeum 和 Dasypyrum 的染色体组。七倍体植物包含六倍体植物的六个染色体组和一个额外的 Pseudoroegneria 染色体组。非九倍体细胞型在其基因组组成上存在差异，反映了通过减数分裂和未减数配子融合的不同起源。E. ×mucronata 中重复序列（5S rDNA、18S rDNA 和 pSc119.2）的杂交模式在细胞型之间和内部均有所不同。在亲本物种中未发现的染色体改变在七倍体和一些非九倍体植物中均有发现。
结果证实，Elytrigia 异源多倍体中既发生同源杂种化，也发生异源杂种化，导致单个杂种基因组中同时存在四个不同的单倍体。在七倍体和一些非九倍体植物中观察到的染色体改变表明，基因组重排发生在杂种形成期间和/或之后。此外，在一个非九倍体中检测到的特定染色体易位表明它不是原始杂种。因此，至少有一些杂种是可育的。小麦族异源多倍体中的杂交明显显著促进了基因组多样性。不同亲本单倍体的组合以及染色体改变可能导致独特谱系的建立，从而为选择提供原材料。
