Influence of Excessively High Temperatures on the Fruit Growth and Physicochemical Properties of Shiranuhi Mandarin in Plastic-Film Greenhouse Cultivation.

Misun Kim,Jaeho Joa,Yosup Park,Sock-Beom Kang,Seok Kyu Yun,Sang Suk Kim

doi:10.3390/plants10081525

Abstract

Excessively high temperatures frequently occur between spring and late fall because of global warming. These problems have a negative effect on fruit production capacity and actual production. However, there is a lack of information on the effects of excessively high temperatures (exceeding the optimum range) on the growth of citrus fruits. Thus, the objective of this present study was to determine the effects of excessively high temperatures on Shiranuhi mandarin fruit growth, physiological characteristics, amino acid contents, and antioxidant activity. In this study, five different high-temperature treatments were applied: normal atmospheric temperature (Con), Con + 4 °C during the day (D4), Con + 8 °C during the day (D8), Con + 4 °C during the night (N4), and Con + 4 °C during the day and night (DN4). The total soluble sugar contents were lowest in D8, and the acid content under DN4 was significantly lower than that under Con. Rising temperature during the day or night affected the colouration of the rind, and the free sugar composition ratio under D8 was lower than those under the other treatments. The total amino acid content tended to increase with increasing temperature during the day. The total flavonoid and total phenolic contents in the peel were significantly higher under Con and N4 than the other treatments and in the pulp under Con.

Highlights

Shiranuhi mandarin [(Citrus unshiu × C. sinensis) × C. reticulata], a late-harvest cultivar developed in Japan, was introduced to Korea in the 1980s
Under the high temperatures prevailing in the tropics, citrus fruit development is fast, and the fruits become very large
The heat unit requirements for the maturation of Valencia oranges grown in cool regions is twice that of Valencia oranges grown in tropical regions [11]

Summary

Introduction

Shiranuhi mandarin [(Citrus unshiu × C. sinensis) × C. reticulata], a late-harvest cultivar developed in Japan, was introduced to Korea in the 1980s. This cultivar is the most popular late-harvest cultivar in Korea on the basis of cost-benefit analysis. The Shiranuhi mandarin cultivation area is increasing in Jeju, the main production area, and along the southern coast. By applying a climate change scenario, Moon et al [1] studied the possible effects on the cultivation of Satuma and Shiranuhi mandarin. The authors predicted that the cultivation of Satuma mandarins would decrease, while the cultivation of late-harvest cultivars such as Shiranuhi mandarins would increase. Abnormal weather conditions are frequent worldwide, and high temperatures have occurred in Korea throughout the past decade from

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