Effects of elevated temperatures during the flowering to physiological fruit drop stage and at the fruit maturation stage on fruit quality of the satsuma mandarin

In recent years, peel puffing and delayed peel pigmentation have been observed in satsuma mandarins, possibly due to global warming. The effects of elevated temperatures during fruit maturation on fruit quality have been well studied. However, little is known about the effects of elevated temperatures during the flowering to physiological fruit drop stage. To clarify this, we controlled the air temperatures around satsuma mandarin trees during the flowering to physiological fruit drop stage (Period A) and at the fruit maturation stage (Period B). Temperatures were set to 2 degrees C or 4 degrees C above the recent mean temperatures because global warming is predicted to increase the mean global surface temperature by 2 degrees C-4 degrees C in this century. We then investigated the effects of the elevated temperatures on fruit quality in varying combinations for Periods A and B. Peel puffing was increased when temperatures were increased by 4 degrees C during Period A or by 2 degrees C or 4 degrees C during Period B. Peel puffing was also increased with increases of 2 degrees C during Period A; however, those results were not statistically significant. Peel pigmentation was enhanced when temperatures were increased by 2 degrees C or 4 degrees C during Period A but deteriorated when the temperature was increased by 2 degrees C during Period B. Fruit weights were increased when temperatures were increased during Period A, but this was partly due to higher peel percentages. The peel percentages tended to be higher after temperature increases in either Period A or Period B. The soluble solid concentrations and acidity levels of the fruit juices tended to be lower after temperature increases during Period A, although not all of those changes were statistically significant. In conclusion, we found that temperature increases of 2 degrees C or more above the recent mean temperatures during early fruit development can be detrimental to fruit quality by increasing peel puffing.