Location: National Clonal Germplasm RepositoryTitle: Karyotype analysis in octoploid and decaploid wild strawberries, Fragaria (Rosaceae)) Author
Submitted to: Cytologia
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/30/2010
Publication Date: 12/1/2010
Citation: Nathewet, P., Hummer, K.E., Iwatsubo, Y., Sone, K., Yanagi, T. 2010. Karyotype Analysis in Octoploid and Decaploid Wild Strawberries, Fragaria (Rosaceae). Cytologia. 75(3):277-288. Interpretive Summary: The 20 wild species of strawberries have differt numbers of chromosome pairs. Some are diploid (have 2 sets of 7). The cultivated strawberry has 8 sets. Another wild species from Iturup Island has 10 sets of chromosomes The chromosomes can be photographed through a microscope producing a "karyotype." The objective of this research was to determine the karyotypes for wild strawberry species. Images of 16 types of American strawberry, and the one from Iturup, were taken at a stage of growth where it is easy to see. The images were taken under a light microscope. We measured the chromosomes and analyzed their differences. These differences showed some relationships of ancestry between species. We found a few unusual types of strawberries that had irregular counts or had more chromosomes than most of the others of their species. The Virginian strawberry had the most variability of the species that we observed. Each of the subspecies could be separated. The strawberry from Iturup Island grouped with the Virginian strawberries rather than the American Chilean type of strawberries.
Technical Abstract: The 20 wild species of strawberries in the genus Fragaria (Rosaceae), have a euploid series including diploid (2n = 2x = 14) through decaploid (2n = 10x = 70) members. Karyotyping has not been thoroughly examined. The objective of this research was to determine the chromosomal morphology and karyotype analysis of wild octoploid and decaploid species in 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. Karyotype analysis was performed on 10 chromosome images. Suggestions of phylogenetic relationships between species were considered based on a cluster analysis of karyotypic similarity. Chromosome numbers of F. chiloensis and F. virginiana genotypes were octoploid (2n = 8x = 56), except for F. chiloensis f. patigonica PI 551462 (2n = 8x - 2 = 54) an aneuploid, and F. virginiana subsp. platypetala PI 551527, a decaploid. Chromosome morphology in F. virginiana subspecies varied more than that in F. chiloensis subspecies. Results of the cluster analyses showed separation between F. chiloensis and F. virginiana subspecies except for F. virginiana subsp. grayana PI 616699. Its karyotype linked to the F. chiloensis clade. The decaploid, F. iturupensis, clustered within the octoploid F. virginiana clade, particularly close to F. virginiana subsp. glauca. The chromosome morphology of F. iturupensis appeared more similar to that of F. virginiana than F. chiloensis subspecies.