Karyotype Analysis in Octoploid and Decaploid Wild Strawberries in Fragaria (Rosaceae)

Karyotype analyses have been useful for clarifying phylogenetic and evolutionary relationships among related species and sub-specific taxa. Within the 22 wild species in the genus Fragaria (Rosaceae), karyotype analyses had been restricted to diploid species. The objectives of this research were to determine the chromosomal morphology and analyze the karyotypes of wild octoploid and decaploid species within this genus. Somatic chromosome images of 16 wild genotypes of F. chiloensis, F. virginiana and F. iturupensis were taken at the metaphase stage of mitosis under a light microscope. To evaluate phylogenetic relationships among 12 accessions, karyotypic similarity was examined by cluster analysis. Chromosome numbers of F. chiloensis and F. virginiana genotypes were octoploid (2n=8x=56), except for PI 551462 (2n=8x−2=54), an aneuploid F. chiloensis subsp. pacifica, and PI 551527, a decaploid genotype of F. virginiana subsp. platypetala. Chromosome morphology in F. virginiana subspecies varied more than that in F. chiloensis subspecies. Results of the cluster analyses separated the F. chiloensis and F. virginiana subspecies, except for F. virginiana subsp. grayana PI 616699. The decaploid, F. iturupensis, clustered within the octoploid F. virginiana clade, and was particularly close to F. virginiana subsp. glauca.