XVI International Botanical Congess

We recently obtained evidence indicating that polyploid formation in wheat was accompanied by several cardinal changes, including rapid nonrandom elimination of specific low-copy, presumably noncoding, DNA sequences from one genome in tetraploid and from two genomes in hexaploid wheat. These sequences exist in all the diploid progenitors but are chromosome or genome specific, i.e., they occur in only one genome, either A, B or D, at the polyploid level. Studying synthetic amphiploids, it was found that sequence elimination occurred soon after polyploidization. This elimination augmented the differentiation of homoeologous chromosomes (partially homologous chromosomes of different genomes) at the polyploid level, thus providing the physical basis for the diploid-like meiotic behavior of polyploid wheat.