Effects of Ambient Temperature during Fruit Development on the Incidence of Reddish-pulp Disorder and Development of Functional Fruit Bag to Control Reddish-pulp Disorder in ‘Shimizu-hakuto’ Peach

Abstract

The occurrence of reddish-pulp fruit was consistently lower in Niimi, Okayama (the north area) than in Okayama City (the south area) in 2013–2016 in field-grown ‘Shimizu-hakuto’ peach. A similar trend was observed in 2016 on comparison with peach trees grown in container boxes, which had been grown in the south area under the same conditions for several years and then transferred to the north area just before the onset of the 2016 growing season. The field temperature in the north area was lower than in the south area by 2°C during the peach fruit growing season in all experimental years. Especially, it was clearly shown that fruit in the south area encountered a higher air temperature (more than 25°C) compared with fruit in the north area during Stage 3 of fruit growth, in which fruit were covered with a fruit bag. These observations suggest that Reddish-pulp fruit disorder is stimulated by a high temperature during the fruit growing season. In order to control the temperature around fruit, a functional fruit bag coated with oxidized titanium, with high light reflecting performance, was developed. Fruit bagging by the functional bag during the growing season lowered the fruit surface temperature by 1.5°C and suppressed the development of Reddish-pulp fruit disorder. Fruit quality such as size, appearance, sugar and pH levels in juice, and harvesting time were not affected by the functional fruit bagging, compared with conventional bagging. The developed functional fruit bag provides a practical technique to control Reddish-pulp fruit disorder.