Budbreak, fruit quality and maturity of ‘Superior’ seedless grapes as affected by Dormex®under Jordan Valley conditions

Abstract

Introduction . In subtropical regions, the lack of or insufficient winter chilling has been one of the most important yield-limiting factors for table grapes. Winter chilling for several weeks is required to cause the transition of both vegetative and floral buds from the dormant to the active state. Thus, the effect of time of application of Dormex® (hydrogen cyanamide) on fruit quality and ripening of ‘Superior’ seedless grape was evaluated under Jordan Valley conditions.Materials and methods . Five-year-old ‘Superior’ seedless vines were pruned on 20 December and sprayed to run-off with a 5% (v/v) concentration of Dormex® at pruning (Dormexprun0 ), 7 d (Dormexprun7 ) or 14 d (Dormexprun14 ) after pruning in comparison with the pruned-only control plants. The date of vegetative budbreak and start of flowering were determined. Fruits were harvested at intervals of 7 d starting from 9 May, with four harvests. Studied data were fruit weight, total soluble solids (TSS), titratable acidity (TA) and maturity with the [TSS:TA] ratio. Results and discussion . All pruned and sprayed vines broke bud 23–46 d after pruning. The (Dormexprun0 ) and (Dormexprun7 ) treatments were the earliest. Compared with the control, Dormex® -treated vines broke bud 4–26 d earlier. All pruned and Dormex® -treated vines started flowering 55–64 d after pruning, with 4–13 d earlier than the control. Fruits of the (Dormexprun0 ) treatment had significantly the highest fruit weight, TSS and the least TA, and it was the only treatment that exceeded the [18:1] (TSS:TA) level. Additionally, higher TSS and lower TA were observed for fruits of Dormex® -treated vines during all harvest dates in comparison with the control. Conclusion . Our study showed that, under southern Jordan Valley conditions, Dormex® should be applied as early as at pruning time to obtain early budbreak and maturity.