EVALUATION OF DORMANCY DYNAMIC AND CHILLING REQUIREMENTS OF MOROCCAN AND FOREIGN APRICOT (Prunus armeniaca L.) CULTIVARS

Local Moroccan apricot has evolved by seedling in traditional oasis of agricultural systems. This population undergoes a local selection made for adaptation to the environment which is characterized by warm and short winters. When chilling requirements are not sufficiently satisfied during winter, variations in the development cycle are caused, affecting bud development, maturity and fruit production. This work focused on characterizing the bud dormancy and estimating the chilling and heat requirements of seven apricot cultivars conducted under Moroccan climate conditions. Dormancy characterization was approached by one-node-cutting biological test. Three models were used to estimate chilling requirements: 0-7°C, Utah and Dynamic; and Growth Degree Hours model to calculate heat requirements. Phenological stages were observed in field to link period of flowering to chilling requirements of each variety. Results showed that the dates of budburst at orchard are spread out during February for all varieties. Leaf fall was early (late November) for Boum4 and relatively late (December 10th) for Marou4, Guer2 and SKH1. For Delpatriarca and Canino, leaf fall happened late in December 19th and 20th respectively. Different patterns of dormancy dynamics were clearly highlighted among apricot cultivars. Divergences concerned mainly the dormancy chronology and intensity, the transition between endodormancy and ecodormancy and the duration of the endodormancy phase. This later was relatively long for KMG6, Delpatriarca and Boum4 especially during the warm year 2007-2008. The average of chilling requirements for all genotypes are ranged between 40,7-49,7 Chill Portions, 420-554 Chill Hours and 704-864 Chill Units according to Dynamic, 0-7°C and Utah models respectively. Flowering took place between the last fortnight of February and early April depending on each genotype. Thus, this population has low chilling requirements. The heat requirements needed for flowering were ranged between 3800 and 8155 Growing Degree Hours. This study showed the adaptation of some local genotypes to the Moroccan climatic conditions and their similar chilling requirements as the Spanish cultivars, which will be useful for farmers to improve tree inter-pollination for an adequate productivity.