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Wilawan Kumpoun, Takashi Nishizawa, Yoshie Motomura, Tanidchaya Puthmee, and Toshiyuki Aikawa

Green mango (Mangifera indica L.) ‘Nam Doc Mai See Thong’ fruit were dipped in 2-chloroethylphosphonic acid solution (50 ppm) for 5 minutes, kept at 25 °C for 3 days, cold stored at 5 °C for 35 days and then transferred to 25 °C for 7 days. The skin color of the cold-stored fruit partly changed to dark-brown with surface depression. In addition, desiccated white-corky pulp tissues developed mainly along to the dark-brownish skin. Histological and biochemical analyses revealed that the formation of white-corky pulp tissues was correlated with starch accumulation in the hypodermal cells. Cell wall polymers of the white-corky pulp tissues were characterized by both a lower amount of solubilized pectins and higher amount of hemicelluloses than those of normally ripened (NR) tissues. The highest fatty acid unsaturation was observed in the NR pulps under chilling conditions followed by the white-corky pulp tissues under chilling conditions and the NR tissues without chilling. These results suggested that the disordered membrane caused by chilling inhibited the subsequent cascade of secondary reactions, such as the cell wall degradation. The skin damage derived from chilling injury (CI) is a direct factor inducing abnormal desiccation in the adjacent pulp, resulting in the formation of white-corky pulp tissues.

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Thanidchaya Puthmee, Kenji Takahashi, Midori Sugawara, Rieko Kawamata, Yoshie Motomura, Takashi Nishizawa, Toshiyuki Aikawa, and Wilawan Kumpoun

The transpiration rate of cuticular membrane and fissures that comprise the netting on fruits of three netted melon cultivars, Life, Andesu, and Gurandoru, were measured during fruit development. Fissures in the equatorial region first developed vertically, then became interconnected by horizontal fissures as the fruit developed. Some cracks remained along the net, even at the fruit ripening stage, regardless of cultivar. Both lignified and suberized cell wall layers in the net tissues of the cultivar Life were thinner than those of the other cultivars, probably because of the shorter developmental period of fruits in the variety. Nevertheless, net transpiration rate did not differ significantly among cultivars at the fruit ripening stage. Peroxidase (POD) activity in the skin tissues of ‘Life’ was lower than that in ‘Andesu’ and ‘Gurandoru’ throughout fruit development and was not correlated with climacteric ethylene production. Among these cultivars, significantly higher ethylene production occurred in ‘Life’ fruit at the ripening stage. This can accelerate membrane permeability of hypodermal tissues, resulting in rapid fruit softening. Our results indicate that the net tissues of netted melons can be as waterproof as cutinized membranes if suberized cell wall layers with wax depositions develop below the net fissures at the fruit ripening stage.