Seasonal Changes in Soluble and Non-Soluble Carbohydrates during and After Dormancy Release in Early and Late Varieties of Apple (Malus Sylvestris, Mill) Trees

Abstract

The flower bud abortion is one of the main problems that limit apple varieties production in the Egypt. Insufficient chilling during the dormancy period is known as the main factor of this problem. One of the hypotheses to explain this problem is that the starch mobilization and carbohydrate fluxes to the buds are impeded when mild temperatures occurred during winter. In order to produce the physiological bases for choosing early- opining apple varieties that may avoid the depleted low winter temperatures, the terribly early and late- opining apple variety Barkhar, Local and Strakhan (Malus domestica) were used to study the relation between the seasonal changes and balance of water, dry weight and carbohydrates metabolism and opining time. This study investigated potential variations in chilling requirements, bud burst and development in early and late varieties of apple trees. The budburst and carbohydrates metabolism of flower and vegetative buds of early and late varieties were additionally investigated. Results showed less bud burst in late varieties than in early ones. In the former, there were increased in water, dry weight and soluble carbohydrates (sugars) at budburst. Although non-soluble carbohydrates levels was considerably reduced by bud development in all varieties. We conclude that late varieties (Strakhan) are less economical in manufacturing new growth, as indicated by less bud vigor at budburst than early varieties (Barkhar and local) and show a marked differential in water content and carbohydrates metabolism throughout bud development compared to early varieties.