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  • Author or Editor: Seung-Hee Lee* x
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To maintain appropriate tree shapes for Asian pear trees, multi-leader system would be more suitable, which could be obtained from the proper training systems. Controlling apical dominance should be the major factor for tree shape management and this might be modified by branch bending or pruning methods. When the tree shape was managed with Alternate Fan System, too narrower branch angle depressed flower bud formation because of the vigorous shoot growth but too wider angle also decreased that formation because of the numerous water sprouts. The tree with 75 degrees of internally deviated angle performed superior result in fruiting process. Additionally, heading-back pruning could be another for water sprout emerging. For that reason, the severer heading-back pruning stimulated the more water sprout emerging. The proper pruning method could be obtained by considering the relation between main stem width and sum of remained branch width.

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Dry heat treatment (DHT), a powerful and agrochemical-free means of inactivating seed-borne virus and other pathogens, has been extensively used for value-added vegetable seeds in Korea, Japan, and some other countries. Since seeds are treated with extremely high heat (75 °C or higher) for a long time (72 h or longer), heat-induced phytotoxicity symptoms are frequently observed. Even though various internal and external factors, such as seed maturity and vigor, maximum temperature and duration of DHT, are known to influence the severity of phytotoxicity, precise control of seed moisture contents during DHT is regarded as one of the most important factors for successful DHT. In an ideal condition using a specifically designed DTH machine, seed moisture content of bottle gourd, initially around 6.20% to 0.64% when stored in a storage room with 50% RH, decreased by 1% after 24 h at 35 °C (5.20% to 0.23%), and further decreased below 4% after 24 h pretreatment at 50 °C (3.64% to 0.37%). The seed moisture content was further reduced down to about 2% after 72 h DHT at 75 °C (2.16% to 0.28%). During the post-treatment conditioning at 50 °C and 70% RH for 24 h, the moisture contents were raised to about 6%(5.94% to 0.45%), thus approaching the initial moisture content of 6% to 7%. During the germination period, treated seeds showed slower absorption of water as compared to the intact seeds, thus suggesting that this slow absorption of initial moisture absorption may be responsible for the slow initial germination frequently observed in treated seeds. Final germination and seedling vigor were not affected by DHT.

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