The three tetraploid species shared the same numbers
of rDNA sites, which were four for 5S and twelve
for 25S rDNA (Figures 3B-3D). These numbers are
twice the numbers of two 5S and six 25S sites detected
in most diploids, and each of the tetraploids’ 5S rDNA
sites was co-localized with a 25S rDNA site. Although
the number and position of rDNA sites was strictly
consistent among the tetraploids, differences in signal
size and intensity among sites were observed. In F.
gracilis (Figure 3C) and F. tibetica (Figure 3D), 25S
rDNA sites among three homologous chromosome
groups were not of noticeably different signal intensities,
while in F. corymbosa (CFRA 1911, Figure 3B),
25S rDNA sites in one “single-marked” group of four
chromosomes had larger signals than those of the
other two groups. Also, among the total four 5S rDNA
sites in F. corymbosa, two were larger and stronger
than the other two.