| dc.description.abstract | Bud-break in grapevines (Vitis vinifera L) can be poor and uneven in locations that have warm winters
with insufficient chilling. Growers in these regions use hydrogen cyanamide (HC), a dormancy-breaking
compound, to increase and synchronise bud-break. Previous studies demonstrated that HC upregulates
the expression of select genes encoding enzymes belonging to the ascorbate glutathione cycle (AGC)
(glutathione reductase, VvGR) to the oxidative pentose phosphate pathway (oPPP) (glucose-6-phosphate
dehydrogenase, VvG6PD) and a key enzyme for dormancy release (1,3- -glucanase, Vv GLU). Here, the
expression of these genes was studied in grapevine buds throughout the natural progression of endodormancy
(ED) and under the effects of the dormancy-breaking compounds, HC and sodium azide. Although
gene expression increased with the progression of ED until mid-May, in early-June they turned off transiently
and reappeared in mid-July before bud-break. The upregulation of these genes under both natural
and artificial conditions suggests that dormancy-breaking compounds activate the same metabolic pathways
that are naturally activated during the bud-ED release process. However, in contrast with the effects
of dormancy-breaking compounds, artificial chilling did not upregulate the above genes. | |
