Karyotype Analysis in Wild Diploid, Tetraploid and Hexaploid Strawberries, Fragaria (Rosaceae)

The strawberry, genus Fragaria (Rosaceae), has a basic chromosome of x=7, and is comprised of 20 wild species having an euploid series from diploid (2n=2x=14) through decaploid (2n=10x=70). Few karyotypes of species in this genus have been reported. The objective of this research was to determine the chromosomal morphology and karyotype analysis of wild diploid, tetraploid and hexaploid Fragaria species. Somatic chromosome images of 20 genotypes of diploids, tetraploids, and hexaploids were taken at the metaphase stage of mitosis under a light microscope. Karyotype analysis was performed in 17 accessions. The phylogenetic relationships between species were constructed using cluster analysis based on karyotypic similarity. Somatic chromosome numbers of wild diploid, tetraploid and hexaploid species were 2n=2x=14, 2n=4x=28 and 2n=6x=42. Chromosome morphology in wild diploid species had greater uniformity than that in the tetraploid species. Results of the cluster analysis showed that the diploid and tetraploid species reside in separate clades, with one exception. Fragaria tibetica, a tetraploid, clustered with the diploid species clade. The hexaploid, F. moschata, clustered with the tetraploid species clade.