Microsatellite Mutation Rate during Allohexaploidization of Newly Resynthesized Wheat

Simple sequence repeats (SSRs, also known as microsatellites) are known to be mutational hotspots in genomes. DNA rearrangements have also been reported to accompany allopolyploidization. A study of the effect of allopolyploidization on SSR mutation is therefore important for understanding the origin and evolutionary dynamics of SSRs in allopolyploids. Three synthesized double haploid (SynDH) populations were made from 241 interspecific F-1 haploid hybrids between Triticum turgidum L. and Aegilops tauschii (Coss.) through spontaneous chromosome doubling via unreduced gametes. Mutation events were studied at 160 SSR loci in the S-1 generation (the first generation after chromosome doubling) of the three SynDH populations. Of the 148260 SSR alleles investigated in S-1 generation, only one mutation (changed number of repeats) was confirmed with a mutation rate of 6.74 x 10(-6). This mutation most likely occurred in the respective F-1 hybrid. In comparison with previously reported data, our results suggested that allohexaploidization of wheat did not increase SSR mutation rate.