Karyotype analysis using FISH (fluorescence in situ hybridization) in Fragaria

The karyotypes of Fragaria species, diploid (Fragaria vesca ‘UC-01’, ‘Hawaii-30’, Fragaria nilgerrensis ‘Whiteberry’) and octoploid (Fragaria × ananassa ‘Akihime’), were analyzed using a method based on fluorescence in situ hybridization (FISH), using ribosomal DNA probes (5S rDNA and 45S rDNA). All diploid species of F. vesca and F. nilgerrensis had 2n = 14 chromosomes, while F. × ananassa, an octoploid species, were 2n = 56. The total length of somatic metaphase chromosome was measured as 12.22, 13.61, and 11.19 μm for ‘UC-01’, ‘Hawaii-30’, and ‘Whiteberry’, respectively, and ‘Akihime’ measured 94.23 μm. The karyotypes were composed of 6 pairs of metacentric and 1 pair of submetacentric in ‘UC-01’ and ‘Whiteberry’, and 5 pairs of metacentric and 2 pairs of submetacentric in ‘Hawaii-30’. 5S rDNA loci were detected in 1 pair from ‘UC-01’, ‘Hawaii-30’ and ‘Whiteberry’, and 45S rDNA loci were detected in 3 pairs from ‘UC-01’ and ‘Hawaii-30’, whereas 45S rDNA loci were detected in 2 pairs from ‘Whiteberry’. In octoploid strawberry ‘Akihime’, 45S rDNA signals were observed at 12 chromosomes, and 5S rDNA signals were observed at 2 chromosomes.