D ECAPLOIDY IN FRAGARIA ITURUPENSIS (ROSACEAE) 1

The strawberry genus, Fragaria (Rosaceae), has a base chromosome number of x = 7. Cultivated strawberries ( F. × ananassa nothosubsp. ananassa ) are octoploid (2 n = 8 x = 56) and fi rst hybridized from F. chiloensis subsp. chiloensis forma chiloensis × F. virginiana subsp. virginiana . Europe has no known native octoploid species, and only one Asian octoploid species has been reported: F. iturupensis , from Iturup Island. Our objective was to examine the chromosomes of F. iturupensis . Ploidy levels of wild strawberry species, include diploid (2 n = 2 x = 14), tetraploid (2 n = 4 x = 28), pentaploid (2 n = 5 x = 35), hexaploid (2 n = 6 x = 42), octoploid (2 n = 8 x = 56), and nonaploid (2 n = 9 x = 63). Artifi cial triploid (2 n = 3 x = 21), tetraploid, pentaploid, octoploid, decaploid (2 n = 10 x = 70), 16-ploid, and 32-ploid plants have been constructed and cultivated. Surprisingly, chromosome counts and fl ow cytometry revealed that F. iturupensis includes natural decaploid genotypes with 2 n = 10 x = 70 chromosomes. This report is the fi rst of a naturally occurring decaploid strawberry species. Further research on F. iturupensis and exploration on northern Pacifi c islands is warranted to ascertain the phylogeny and development of American octoploid species.