Yang Fan, Wan Hongshen, Li Jun, Wang Qin, Yang Ning, Zhu Xinguo, Liu Zehou, Yang Yumin, Ma Wujun, Fan Xing, Yang Wuyun, Zhou Yonghong
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, China.
Key Laboratory of Wheat Biology and Genetic Improvement in Southwestern China (Ministry of Agriculture and Rural Affairs of P.R.C.), Crop Research Institute, Sichuan Academy of Agricultural Sciences, Chengdu, China.
Front Plant Sci. 2022 Jun 29;13:883868. doi: 10.3389/fpls.2022.883868. eCollection 2022.
Allohexaploidization and continuous introgression play a key role in the origin and evolution of bread wheat. The genetic bottleneck of bread wheat resulting from limited germplasms involved in the origin and modern breeding may be compensated by gene flow from tetraploid wheat through introgressive hybridization. The inter-ploidy hybridization between hexaploid and tetraploid wheat generates pentaploid hybrids first, which absorbed genetic variations both from hexaploid and tetraploid wheat and have great potential for re-evolution and improvement in bread wheat. Therefore, understanding the effects of the pentaploid hybrid is of apparent significance in our understanding of the historic introgression and in informing breeding. In the current study, two sets of F populations of synthetic pentaploid wheat (SPW1 and SPW2) and synthetic hexaploid wheat (SHW1 and SHW2) were created to analyze differences in recombination frequency (RF) of AB genomes and distorted segregation of polymorphic SNP markers through SNP genotyping. Results suggested that (1) the recombination of AB genomes in the SPW populations was about 3- to 4-fold higher than that in the SHW populations, resulting from the significantly ( < 0.01) increased RF between adjacent and linked SNP loci, especially the variations that occurred in a pericentromeric region which would further enrich genetic diversity; (2) the crosses of hexaploid × tetraploid wheat could be an efficient way to produce pentaploid derivatives than the crosses of tetraploid × hexaploid wheat according to the higher germination rate found in the former crosses; (3) the high proportion of distorted segregation loci that skewed in favor of the female parent genotype/allele in the SPW populations might associate with the fitness and survival of the offspring. Based on the presented data, we propose that pentaploid hybrids should increasingly be used in wheat breeding. In addition, the contribution of gene flow from tetraploid wheat to bread wheat mediated by pentaploid introgressive hybridization also was discussed in the re-evolution of bread wheat.
异源六倍体化和持续渐渗在普通小麦的起源和进化中起着关键作用。普通小麦起源和现代育种中涉及的种质有限所导致的遗传瓶颈，可能通过四倍体小麦渐渗杂交产生的基因流得到弥补。六倍体和四倍体小麦之间的倍间杂交首先产生五倍体杂种，这些杂种吸收了六倍体和四倍体小麦的遗传变异，在普通小麦的再进化和改良方面具有巨大潜力。因此，了解五倍体杂种的效应对于我们理解历史渐渗和指导育种具有明显意义。在本研究中，创建了两组人工合成五倍体小麦（SPW1和SPW2）和人工合成六倍体小麦（SHW1和SHW2）的F群体，通过SNP基因分型分析AB基因组的重组频率（RF）差异和多态性SNP标记的偏分离情况。结果表明：（1）SPW群体中AB基因组的重组率比SHW群体高约3至4倍，这是由于相邻和连锁SNP位点之间的RF显著增加（<0.01），特别是在着丝粒周围区域发生的变异，这将进一步丰富遗传多样性；（2）根据前一种杂交组合中发现的较高发芽率，六倍体×四倍体小麦杂交可能是产生五倍体衍生物的有效方法，比四倍体×六倍体小麦杂交更有效；（3）SPW群体中偏向母本基因型/等位基因的偏分离位点比例较高，可能与后代的适应性和存活率有关。基于所呈现的数据，我们建议在小麦育种中应更多地使用五倍体杂种。此外，还讨论了四倍体小麦通过五倍体渐渗杂交介导的基因流对普通小麦再进化的贡献。
