On the other hand, Fukui and Iijima (1991) reported that rice
chromosomes are very small in the metaphase stage, but are 2–3
times larger in the pro-metaphase stage. In addition, Fukui et al.
(1998) reported the possibility of identifying morphological
characteristics of pro-metaphase chromosomes in diploid
Brassica species, which have small chromosomes at the
metaphase stage. Results described in those papers imply that
pro-metaphase chromosomes are larger and easier to identify
than those at the metaphase stage in strawberry plants.
However, few reports have described chromosome preparation
and staining methods for somatic pro-metaphase chromosomes
in strawberry plants. The phylogenetic relationships in the
genus Fragaria and origin of octoploid strawberries could be
clarified by karyotype analysis using fluorescence in situ
hybridization (FISH) if a method was developed to obtain good
images of somatic chromosomes at the pro-metaphase stage.
This paper presents methods of chromosome preparation
and staining in Fragaria vesca (2n = 14) and Fragaria
ananassa (2n = 56) to obtain clear images of well-spread
somatic metaphase and pro-metaphase chromosomes.