Agriculture & Food, Volume 9, 2021

Abstract: Climate anomaly has affected the rates of chilling accumulation, which are vital for flowering and production in temperate fruit trees. As an adaptation to cold winter orchards enters a period of dormancy designed to protect cold-sensitive tissues such as shoots flowers from freezing injury. Successful release from dormancy requires a specific minimum cold temperature requirement to be met for growth to resume when the temperature warms in spring. This cold temperature is specific and referred to as the “chilling requirements”. The present study aimed to use the relationship between the state of chilling and the state of swelling of buds and flowering of cherry and peach for 10 stations in Bulgaria, during the period 2000-2015 and daily chill accumulation. The buds remain dormant until they have accumulated sufficient chilling units (CU) of cold weather. When enough chilling accumulates, the buds are ready to grow in response to warm temperatures. If there have been enough CU’s, the flower and leaf buds develop normally. If the buds do not receive sufficient chilling temperatures during winter to completely release dormancy, trees will develop one or more of the physiological symptoms associated with insufficient chilling: 1) delayed folia appearing; 2) reduced the number of the fruits, and increased butonisation; 3) reduced fruits quality.