Genomic Varation In The Synthetic Wheat Induced By Allopolyploidization

Common wheat (Triticum aestivum L.,2n=6x=42,AABBDD) is a good example of allopolyploid made up of the three diploid genomes A, B and D. By the mimic of common wheat origination,many synthetie hexaploid wheats have been produeed by T. turgidum L(2n=4x=28,AABB) and Ae. Tauschii (2n=2x=14, DD), the intercrossing between T. turgidum (maternal) and Ae. tauschii followed by chromosome doubling. It is convenient to transferred the excellent genes to the common wheat from the T. turgidum L or Ae. tauschii using the synthetie hexaploid wheats as a bridge parent. Synchronously, the amphiploid can be used to explore the mechanism of the allopolyploidization. There are mang repeated sequences in the wheat genome, and in particular the simple sequence repeats are proposed to the important compositive element of the plant genome. SSR can be used to differentiate the diversity among the species based on the different repeat units exsited in microsatellite. SSR has been a important tool for studying the genomic varation and evolution about the species.In this study, we analyzed microsatellite(SSR) products of the genome of ten newly synthetic wheats and their parents (they were divided into two group according to their parents, the five synthetic wheats in the first group were created from the same T.turgidum L and five different Ae.tauschii, the five synthetic wheats of the second group were developed from the same Ae.tauschii and five different T.turgidum L.), to understand the effect of the wheat genome about allopolyploidization and microsatellite. The results were as follows:(1) Compared to the parents, the proportions of the varation between the synthetic wheats and their parent in the first group were listed below: G-SSR was 4.6%, EST-SSR was 2.6%, and STS was 0. Similarly, the proportions of the varation between the synthetic wheats and their parent in the second group were that G-SSR was 38.6%, EST-SSR was 11.8%, and STS was 0. The results showed that the vararation in the non-coding region was much more than coding region, the different materials were responsed differently to allopolyploidization, the unconstant Syn44, Syn98 and Syn68 may be provided fine material for gaining further insight into the genomic events that accompany allopolyploid formation.(2) The synthetic wheats and their parents of two groups were scanned by the markers on the whole genome of A, B, D, so sequence elimination of the synthetic wheats from their parents may be a common phenomenon by alloploypoidization.(3) The locus sequences amplified by 31 microsatellite on the genome of A, B and D were cloned and sequenced, and the sequences analyses indicated that the difference presented on the SSR locus was mainly due to the variation of the number of repeat units either in the synthetic wheat and/or the donor parents. However, no any variation was detected in the flanking regions of the newly synthetic hexaploid wheat. Microsatellites are more active than the coding sequences, which consequently resulted in high polymorphism in different species. Microsatellites may play an important buffering role to achieve genome stability in allopolyploid synthesis if they cannot be discerned any coding function.