Abstract
This study was carried out during the two successive seasons of 2016 and 2017 to investigate the impact of dormex, dormex plus mineral oil, dormex plus potassium nitrate, dormex plus calcium nitrate and dormex plus thiourea on bud break, growth, yield and some chemical constituents of Malus sylvestris "Ein Shamer". The trees were grown in loamy sand soil, and sprayed with six treatments (dormex (4%), (dormex (2%) plus mineral oil (2.5%),(dormex (2%) plus potassium nitrate (4%),(dormex (2%) plus calcium nitrate (4%) and (dormex (2%) plus thiourea (1%) and control. Generally, it was found that all studied growth parameters , date of flower bud break, percentage of bud break, fruit-setting ,fruit weight, fruit size, fruit number/tree, yield/tree (kg) and some chemical constituents of leaves (total chlorophyll ,total carbohydrates, total protein, nitrogen, phosphorous and potassium contents) and some chemical constituents of fruits (total soluble solids(T.S.S.), T.S.S/ acid ratio, vitamin C, water content %, total free amino acids, total carbohydrates, total sugars and reducing sugars) were increased with the application of the different treatments. The best results were obtained from the treatments of dormex at 4% followed by (dormex (2%) plus mineral oil (2.5%). On the contrary, the same treatments decreased total acidity and total phenols in fruits as compared to the control. It could be recommended to use dormex at 4% and (dormex (2%) plus mineral oil (2.5%) for improving bud break, growth, yield and chemical constituents of apple trees or fruits.
Highlights
The apple tree is a fruit-bearing deciduous temperate climate, which requires a certain amount of winter cold to overcome its lethargy, a physiological condition that occurs annually to survive cold winters [1],[2],[3],[4],[5],[6],[7],[8]
1- Control 2- Spraying with dormex at rate 4% 3- Spraying with dormex at rate 2% plus mineral oil at rate 2.5% 4- Spraying with dormex at rate 2% plus potassium nitrate at rate 4% 5- Spraying with dormex at rate 2% plus calcium nitrate at rate 4% 6- Spraying with dormex at rate 2% plus thiourea at rate 1%
A - Date of flower bud break: Data presented in Table (2) clearly indicated that spraying apple trees with all the tested substances hastened the beginning of flower bud break as compared to the control
Summary
The apple tree is a fruit-bearing deciduous temperate climate, which requires a certain amount of winter cold to overcome its lethargy, a physiological condition that occurs annually to survive cold winters [1],[2],[3],[4],[5],[6],[7],[8]. It is difficult to determine the precise amount of cold that is required to get out of lethargy [9],[10],[11],[12],[13] This deficiency of cold affects a late sprouting in terminal buds, a poor and irregular flowering, large number of buds without sprouting, low fruit tie, low production and poor quality, as well as an increased risk of fire blight [15],[16]. Among the compensators mentioned in the literature and that have been applied are: calcium nitrate, potassium nitrate, mineral oil, thiourea, garlic extract, onion extract, dormex (hydrogenated cyanamide), aminoburts, semitrol, break trhu, Tecno Oil 100EW, calcium nitrate, revent, promalin, biozyme, thidiazuron (TDZ) and erger which widely used for stimulating bud break in various fruit species [14], [17],[18],[19],[20],[21],[22],[23],[24],[25].
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