Even though the A genome of bread wheat and that of the diploid ancestor can form perfect bivalents during meiosis in the F 1 s of AAB ( Gill et al., 1988 ), there are likely to be significant differences in base sequences and chromosome structures (such as inversion, translocations, deletion/duplications, or heterochromatin structures) after the tetraploid wheat formation – i.e., 100,000–500,000 years ago ( Huang et al., 2002 ).
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