A near-complete reference genome of the strawberry is reported in a paper published online this week in Nature Genetics. This genome provides new insights into the origin and evolutionary history of this popular fruit.
The cultivated octoploid strawberry (Fragaria × ananassa cultivar ‘Camarosa’) has eight sets of chromosomes. Also known as the garden strawberry, it is popular for its flavours and aromas.
Patrick Edger and colleagues report a high-quality assembly and annotation of the octoploid strawberry genome, identifying more than 100,000 strawberry genes. The authors sequenced 31 sets of RNA molecules from diploid Fragaria species (strawberry species with two sets of chromosomes) and compared the sequences of expressed genes of diploid species with those of F. × ananassa. The authors were then able to identify Fragaria vesca, Fragaria iinumae, and previously unknown Fragaria viridis and Fragaria nipponica as four diploid ancestral species of F. × ananassa, according to evolutionary analysis. These analyses, combined with the geographic distributions of extant species, suggest that the octoploid strawberry originated in North America.
In addition, the authors analysed the evolutionary dynamics among the four subgenomes of the octoploid strawberry. This analysis revealed the presence of a single dominant subgenome, which largely controls metabolomic and disease-resistance traits in strawberry.
The authors conclude that the evolution and origin of strawberry and the discovery of a dominant subgenome, along with the first high-quality genome for an octoploid strawberry, may provide a powerful resource for researchers and breeders to improve the flavors, aromas and disease resistance of the cultivated garden strawberry.