Peach fruit is susceptible to two types of flesh disorders, called “water-soaked flesh browning disorder” (Browning disorder) and “red flesh disorder.” It is difficult to confirm the presence of these disorders based on the exterior appearance of the fruit. These disorders have been frequently reported, mainly in regions of southwestern Japan, such as Wakayama, Okayama, and Kyusyu, which experience higher temperatures and precipitation during summer than do eastern and northern Japan. In addition, we confirmed that higher temperature and rainfall played a role in causing these disorders, in this study. Therefore, it is important to control temperature and the water content in fruit trees during summer to reduce the incidence of the disorders.

As a countermeasure to control fruit temperature, we developed new fruit bags that can shut off infrared rays effectively and can suppress high temperatures in the fruit, by using a titanium oxide (JR-1000) coating on the surface of the bag (dot-type coating), while maintaining moisture permeability. These fruit bags have been recognized to restrain temperature increase of the fruit at high temperatures in summer. This can decrease the occurrence of both red flesh disorder and water-soaked flesh browning disorder caused by high temperatures. No significant difference was found in fruit quality between the new fruit bag and the conventional bag. Combined use of this bag with moisture-permeable plastic multi-sheet results in higher reduction of these disorders.

The countermeasure to control excess water of the peach trees is the use of moisture-permeable plastic multi-sheet, which is made of ultra-thin plastic material. However, moisture in the soil can evaporate into the atmosphere through micro-pores in the plastic multi-sheet. The soil surface under tree canopy should be covered from 40 days after full bloom until the harvest to cut off a large amount of water in the rainy season and summer. It is necessary to cover approximately 50% of the tree canopy around the trunk. The use of this plastic multi-sheet could suppress the occurrence of flesh disorders in peach fruit due to excess water absorption by the tree.
　
As mentioned before, it is difficult to confirm the presence of these disorders based on the exterior appearance of fruit, except in fruit with obvious disorder. It is necessary to distinguish disordered fruit from healthy ones using non-destructive methods. We established a non-destructive method that uses acoustic vibration. When a fruit receives vibration, the resonant frequency in the fruit differs, depending on the hardness or the extent of disorder of the fruit. This is a novel method that examines the features of the different resonant frequencies for estimating the state of the fruit.

http://www.okayama-u.ac.jp/user/agr/up_load_files/freetext/nougaku02_8_ja/img/contents.pdf

Contact information

Contact information
Kunihisa MORINAGA, Ph. D. (Professor)
Graduate School of Environmental and Life Science, Okayama University
Email: forest（a）okayama-u.ac.jp
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