Potential Effects of Temperature Differences on the Soluble Sugar Content in Pear Fruit during the Growing Seasons of 2018 and 2019

The impacts of climate change on crop yields and fruit quality are projected to accelerate with increased atmospheric carbon dioxide levels; however, few studies have focused on the impacts of climate change on the accumulation pattern and content of soluble sugars in pear (Pyrus pyrifolia) fruit. We compared the soluble sugars content and accumulation patterns during the 2018 and 2019 growing seasons throughout the developmental stages of pear fruit with climate data collected over the same period. Between the two years, we observed differences in the fructose and sucrose contents at the maturation stage of the pear fruit, resulting from differences in sugar accumulation following 132 days after full bloom (DAFB). Differences were also found in the meteorological data measured over the two years. In particular, the daily average temperatures from late-June to mid-August (73 to 132 DAFB) were all higher in 2018 than in 2019, and differences in the cumulative amounts of both fructose and sucrose were observed since 132 DAFB. Notable differences were confirmed in the comparison of the meteorological variables for each time interval. Among the meteorological variables, those related to temperature showed clear differences between the two years. Correlation coefficient matrices showed that sucrose and fructose accumulation responded differently depending on the meteorological variables over the two years. Furthermore, only accumulated temperature and air temperature were correlated with changes in the sucrose and fructose content in 2018, unlike in 2019. Taken together, our results indicate that temperature differences may have contributed to differences in the fructose and sucrose contents and their accumulation patterns over the two years.