XVI International Botanical Congess
The three cultivated polyploid Brassica species have evolved relatively recently by interspecific hybridization of existing diploid species or close relatives. Evidence for polyphyletic origins explains some of the genetic variation observed within these polyploid species. However, variation also exists within apparent monophyletic groups. To investigate the potential importance of rapid genome evolution creating new variation, we resynthesized the Brassica polyploids by interspecific hybridization and chromosome doubling. Our initial molecular analysis indicated extensive changes in nuclear RFLP patterns that could be explained by changes in DNA methylation and possible genomic rearrangements. More recently, we have detected heritable changes in flowering time among sublines derived from single homozygous genotypes of resynthesized B. napus. Some of this novel variation maps to genomic regions that control flowering time variation in natural populations. Thus, there may be common genetic pathways that are affected by evolution to create variation for important adaptive traits.