Response of “Anna” apple dormant buds and carbohydrate metabolism during floral bud break to onion extract

The response of dormancy release of “Anna” apple buds, carbohydrate metabolism and hydrolytic enzymes activities to 13-year-old trees foliar application with onion extract was investigated. Selected trees were sprayed with four extract rates (50, 100, 150 and 200 ml l−1) and tap water as a control. Our results showed that breaking bud dormancy increased as the extract concentration increased. Increases in reducing sugars and hydrolytic enzymes (α-amylase and invertase) activities, and reductions in non-soluble carbohydrates and non-reducing sugars were correlated with the increase in the percentage of floral bud break and the reduction in flowering duration as a result in the extract application. The variance in the timing of soluble sugars accumulation/exhaustion processes in the extract treated-trees and the control may be accounted for the variance in flowering duration and floral bud break timing. The best results were obtained with the extract concentration of 200 ml l−1, which could be recommended for early and high floral bud break percentage by regulating the metabolism of carbohydrates and the activities of hydrolytic enzymes in apple floral buds.

► “Anna” apple bud break% maximized with onion extracts foliar application.
► Onion extracts hastened bud break and shortened flowering duration.
► Carbohydrate metabolism improved in buds by onion extract.
► Onion extract play an important role in bud release from dormancy.