A previous rDNA-FISH technique performed on F.
vesca enabled the construction of a karyotype with three
pairs of marked chromosomes in diploid strawberry
[27]. Confirmatory results were obtained in our lab
recently on F. vesca ’Hawaii 4’ [28]. For most accessions
of F. vesca, our data presented here are congruent with
the two previous studies. Among the three pairs of
chromosomes with rDNA markers, one pair is double
marked by 25S and 5S rDNA, and the other two single
marked pairs can be distinguished by their different size
and/or signal intensities of 25S sites they bear. The
other eight chromosomes in a diploid complement are
still challenging for even matching of homologs, except
for the largest pair, which can be grouped by its size in
most cells. To date, various genomic resources for F.
vesca including a fosmid library [47], mapped and annotated
fosmid clones [10], a BAC library [48], and the
draft ‘Hawaii 4’ genome [28] have been established.
Assembly has been anchored to the genetic linkage map
into seven pseudochromosomes. These all give good
opportunities for developing new, chromosome-specific
probes that can expand the scope of karyotypic resolution
in Fragaria.