DNA time stamps reveal the strawberry’s surprising origins

Many of the world's most important crops have unusually complex genomes created through repeated rounds of whole-genome duplication and hybridization. These so-called polyploid genomes contain multiple sets of chromosomes inherited from different ancestral species. However, determining exactly how those genomes were assembled can be extremely difficult, especially when the original ancestor species are extinct or unknown. A new study introduces a genome-wide approach for untangling these complex genetic histories. The method takes advantage of evolutionary signatures left behind by long terminal repeat retrotransposons, a type of mobile DNA sequence. By comparing patterns of similarity among these elements across chromosomes, researchers can identify distinct subgenomes and estimate when major genome-merging events occurred. When applied to the cultivated octoploid strawberry, the tech…