Inhibitory Effect of Ethephon on Occurrence of Water-soaked Disorder in the Japanese Pear ‘Akizuki’

Abstract

To elucidate the inhibitory effect of ethephon on the occurrence of water-soaked disorder in Japanese pear ‘Akizuki’ (Pyrus pyrifolia Nakai) fruit, we sprayed fruits with 100 mg·L⁻¹ ethephon solution approximately 120 DAFB in the 2012, 2014, 2015, 2016, and 2017 seasons. Ethephon treatment reduced the incidence and degree of water-soaked disorder at commercial harvest time. There was no significant difference in fruit size or soluble solids content between the ethephon-treated fruits and the control fruits, except for fruit size in the 2012 season. During the nine-day storage period after harvest, water-soaked disorder did not develop in either the ethephon-treated fruits or the control fruits. In addition, flesh firmness and soluble solids content did not differ between the ethephon-treated fruits and the control fruits during the storage period. Ethylene production increased sharply in the ethephon-treated fruits a few days after the ethephon treatment, in contrast to the control fruits. Sucrose content in the ethephon-treated fruits was higher than that in the control fruits on day 10 after treatment. Sorbitol content in the ethephon-treated fruits was lower than that in the control fruits on days 10 and 20 after treatment. Water-soluble, Na₂CO₃-soluble, and total pectin contents were not affected by the ethephon treatment. Hemicellulose, cellulose, and starch contents in the ethephon-treated fruits decreased earlier than those in the control fruits. Sucrose content was lower, but sorbitol and glucose contents were higher, in water-soaked tissue than in sound tissue. These results suggest that ethephon treatment rapidly induces changes in the contents of fruit’s internal components and accelerates fruit maturation, thereby alleviating factors that cause water-soaked disorder in ‘Akizuki’.