Onion Extract Application Effects on Flowering Behavior and Yield, and a few Chemical Constituents of Shoots throughout Dormancy Break in "Anna" Apple Trees

Abstract

Metabolic changes in water content, total carbohydrates, total sugars, reducing sugars, anthocyanin, total free amino acids, proline and total indoles in shoots of "Anna" apple (Malus sylvestris, Mill) trees were investigated during dormancy and bud break under the effect of foliar application of four onion extract rates (5, 10, 15 and 20%). Flowering percentage and fruit yield characteristics (i.e., fruit-set, number of fruits tree-1 and fruit yield tree-1) were increased, while number of days recorded to reach full bloom were reduced with the application of both onion extract rates (15 or 20%). In addition, contents of total carbohydrates, total sugars, reducing sugars, anthocyanin, total free amino acids, proline and total indoles in shoots were significantly increased in floral buds, particularly during bud break. In contrast, the content of free phenols was reduced. The best results were obtained from the rate of onion extract at the level of 20% followed by 15% that could be recommended for early and high percentage of flowering and increased yield by regulating the metabolism of amino acids, including proline and indoles in apple floral buds.