Determination of Chilling and Heat Requirements of Flower Buds in some Peach (Prunus persica L.) Cultivars

This study was carried out to determine the chilling and heat requirements of bud flowers in five peach cultivars (Kosary, Haj Kazemi, Anjiry Asali, Anjiry Zafarany, and Zoud Ras). Determinatal shoots in terms of diameter and length were removed and transported to the laboratory and maintained in a growth chamber weekly. Bud status in the case of phenological stage, dry and fresh weight of buds were measured in all sampling stage. Different models were used for estimating chilling requirement. The heat requirements were calculated as the growing degree hours (GDH) accumulated from breaking of dormancy to the F50 (50% of opened flowers). The results showed that Anjiry Asali had the lowest chilling requirement; while Kosary and HajKazemi had the highest chilling requirement. However, Anjiry Zafarany and Zoud Ras showed moderate chilling requirement. The studied cultivars showed a range of chilling requirements (Utah model), between 746CU and 86 CU. There was a significant difference for bud fresh and dry weight before and after forcing among sampling dates. In the case of heat requirement, Anjiry Zafarany (4099GDH) had lowest and Kosary and Haj Kazemi (4543 GDH) were those with the highest heat requirement. Anjiry Asali (4384 GDH) and Zoud Ras (4232GDH) showed moderate heat requirement.