Changes in Growth, Fruit Quality, and Leaf Characteristics of Apple Tree (Malus domestica Borkh. ‘Fuji’) Grown under Elevated CO2 and Temperature Conditions

Climate change has a considerable impact on human life and ecosystems, as well as on agricultural ecosystems. The two main factors of future climate change, CO2 concentration, and temperature should be tracked, and changes in crop yield and quality due to these environmental factors should be identified. The objective of this study was to analyze the growth, fruit quality, and leaf characteristics of apple trees (Malus domestica Borkh. ‘Fuji’) grown under different elevated CO2 and temperature conditions for extended periods. Four different CO2 concentrations and temperature treatments for the cultivation of apple trees were applied as follows: ambient CO2 concentration and temperature (CON), elevated CO2 concentration and ambient temperature (ECAT), ambient CO2 concentration and elevated temperature (ACET), and elevated CO2 concentration and elevated temperature (ECET). Tree shoot length and fruit fresh weight were measured over nine consecutive years. The soluble solids content, titratable acidity, firmness, Hunter ‘a’ value, and ethylene and CO2 emissions of harvested fruits from 9-year-old trees were measured. Elevated CO2 concentrations promoted shoot growth and average fruit fresh weight but reduced fruit yield at the early stage of development, with more than eight years of recovery. Elevated temperature decreased shoot growth, average fruit fresh weight, and fruit yield, as it caused a decrease in the leaf photosynthetic rate. However, under all climate change conditions, it was predicted that the fruit quality would decrease, thus, the marketability of apples would decrease. In the future, as climate change continues, this study can identify the type of cultivation and management practices needed to maintain the fruit quality of apples.