Results and discussion
Down-regulation of endogenous gene toward
acyanic petunias
Consumers usually appreciate pure while varieties.
Although a pure white petunia was obtained by antisense
suppression of CHS-A from P. hybrida Surfinia Purple
(Figure 3B, Tanaka et al. 1998), it was not as vigorous as
the host and was prone to insect attack. Most likely, the
complete loss of flavonoids resulted in less protection to
various kinds of stress. The white color became unstable
after a few years of cultivation in the greenhouse (Figure
3C). F3H and DFR genes were alternate targets of gene
suppression to obtain white or pale shades of flower
color, and the binary vector pBPFT1 (sense suppression
of F3H gene) and pBPDF1 (antisense suppression of
DFR gene) were constructed (Figure 2) and subjected to
the transformation of the Surfinia Purple Mini. Forty-one
of 65 and 63 of 165 transgenic plants exhibited modified
flower color.
F3H and DFR gene suppression in this study yielded
star-shaped phenotypes (Figure 3D and E). Although
complete suppression of F3H and DFR should yielded
acyanic flowers, only a very pale flower (Figure 3E) was
obtained. DFR gene suppression also yielded a star
shape with spots (Figure 3E). Antisense and sense
suppression of the chalcone synthase-A (CHS-A) gene in
petunia yielded white and variegated flower color (van
der Krol et al. 1988; Napoli et al. 1990). Phenotypic
varieties may depend on the gene of target of suppression
and petunia host varieties.