CHILLING AND HEAT REQUIREMENTS FOR BUD BREAK AND FRUIT DEVELOPMENT OF SOME GRAPE CULTIVARS UNDER ASSIUT CONDITIONS

摘要

The experiments were conducted during two successive seasons of 2002/2003 and 2003/2004 on Perlette, Superior and Flame Seedless grapevines grown at private orchard in Assiut. The objective of this study was to determine the chilling and heat requirements to define the ability of such cultivars to success under Assiut climatic conditions. The three grape cultivars showed growth cessation during a period extended differently among them. Generally, such period was limited between November and December.The endodormancy was considered to be broken when the percentage of bud break reached 50% or more. With endodormancy completion (50% bud break), additional chilling resulted in more increase of bud break percentage till it reached maximum level (over 90% in Perlette and Flame Seedless and over 80% in Superior). As an average of the two studied seasons, the grapevines required 72, 167 and 63 chill units and 173, 291 and 161 chill units according to total hours ≤ 7.2°C and ≤ 10°C, respectively to achieve 50% bud break for the three cultivars, respectively. Generally, Flame Seedless cultivar required G.D.H more than Superior and Perlette cultivars. As an example, fruit ripening required 39122, 37394 and 43336 heat units for Perlette, Superior and Flame Seedless grape cultivars, respectively. Such amount of heat requirements can be fulfilled in 180, 165 and 187 days for such cultivars, respectively. It could be recommended that the studied cultivars can be planted successfully under Assiut (and bordering regions) climatic conditions.