To get a better understanding of the relationship between temperature and fruit quality of apples, 3 apple cultivars, ‘Jonathan’, ‘Golden Delicious’ and ‘Fuji’, eachgrafted on M7 rootstocks, were grown at 13 different locations from Hokkaido down to Kyushu. Mature fruits picked at each location were shipped to Kyoto University where their quality characteristics were evaluated, and the relationships between their fruit quality and heat summation during growing or maturation period were evaluated.
1. Fruit weight, size, and the content of acid and sorbitol showed no significant correlation with the heat summation either in the entire growing season or during the maturation stage, in all cultivars.
2. Correlations between shape index of fruit, flesh firmness, Brix°, and total sugars and the heat summation either in the entire growing season or during the maturation stage were sometimes significant, depending upon cultivars and years.
3. Anthocyanin content in the skin of ‘Jonathan’ fruit was negatively correlated with heat summation, while there was no significant correlation with ‘Fuji’ fruit.
4. In all cultivars, sugar composition in the flesh showed high correlation with heat summation. The lower the heat summation, the more sucrose and the less glucose accumulated.
5. In conclusion, it is suggested that most of the fruit quality characteristics of apples are affected not only by temperature but also by other climatic factors or cultural practices.
However, sugar metabolism in the fruit seems to be greatly affected by temperature.