Methods of evaluating the chilling and heat requirements of apple and pear trees

The change in the occurrence of phenophases in fruit trees gave a challenge to climate change. Changes in average temperatures and rainfall and increased short-and long-term extreme events are already affecting crop yields worldwide. To avoid possible losses, it is necessary to provide helpful information to farmers in real time regarding initiating a particular stage of fruit tree development. Modern breeding programs have launched cultivars with low winter chill requirements onto the market, involving extensive zoning research in recent years. Also, there are species/cultivars with a chilling requirement that can no longer be satisfied in some areas, leading to losses in production/economic inefficiency. Climate change generated significant interest in developing specific tools and models adjusted for each crop. The paper aims to present the available information on apple and pear trees' chilling and heat requirements, focusing on the methods used for their determination. The results reflect comparing the methods used and their efficacity for those species.