Metabolic Changes in Phenolic Compounds in Buds during and after Dormancy Releasing in early and late (Malus sylvestris, Mill) Apple Varieties as Effected by Chilling Requirements

In order to study the relation between seasonal changes in phenolic compounds and flower opining date according to chilling requirements. The early and late-opining apple varieties, Barkhar, Local and Strakhan (Malussylvestris) were used. This study investigated variations in chilling requirements, bud burst and development in early and late varieties of apple trees. Results showed less bud burst in late varieties than in early ones. In the former, there were increased in phenolic compounds (conjugated and total phenols) at budburst in all varieties. As dormancy begins, free phenols are increased, coinciding with a reduction in the levels of conjugated phenols. Consequently, as dormancy breaks, these free phenols are conjugate with organic constituents, and a decrease in the concentrations of free phenols occurs, in order to reduce inhibitory effect on growth. 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 phenols compound pattern throughout bud development compared to early varieties.