S11 - Session P5 - Climate change and the effects of incremental increases in air temperature and CO2 concentrations on the ripening of apple fruit

Authors: Osamu Arakawa *, Daiyu Ito, Rakibul Hassan

To understand the effects of climate change and global warming on apple trees and fruit, we have been researching the effects of high temperatures (an increase of +3℃ from ambient temperatures) and high CO 2 (+200 ppm) levels, combined with normal and increased precipitation, on apple trees and apple fruit using premature (6-year) fruiting trees on M26 rootstocks in large greenhouses. The cultivars tested were early maturing 'Tsugaruhime', a bud sport of 'Tsugaru' with a normal early-September harvest time, and late maturing 'Miyabifuji', a bud sport of 'Fuji' whose normal harvest time is mid-November. Full bloom time was 10 days earlier under both high-temperature and high-temperature with high CO 2 conditions for both 'Tsugaruhime' and 'Miyabifuji'. As for 'Tsugaruhime', the ripening and normal harvest times, determined by the starch index, was 8 days earlier under both high-temperature and high -temperature with high CO 2 conditions than would have occurred under normal conditions. On the other hand, the ripening and harvest time of the 'Miyabifuji' occurred 8 days later than would have been the case under normal conditions. The results showed that the number of days after full bloom until harvest for the 'Tsugaruhime' was almost the same for all treatments. For the 'Miyabifuji', that number was 18 days longer under both high-temperature and high-temperature with high CO 2 conditions than would be expected under normal conditions. Fruit size and weight for both cultivars were significantly higher under high CO 2 conditions when compared to those grown under normal conditions. As for fruit quality, SSC, acidity and firmness were influenced more by precipitation than temperature or CO 2 levels. The results showed that the effects of global warming on apple fruit ripening and quality differ depending on the cultivar.