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  • Author or Editor: Seok-Kyu Jung x
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Fruits of `Tsugaru' (an early maturing cultivar), `Hongro' (mid-season cultivar), and `Fuji' (late cultivar), were harvested at different times of the year, depending upon their maturity, and treated with 1-MCP at 0.0, 0.5, 1.0, and 2.0 ppm for 8-24 hours. Fruits were also treated with 1-MCP at different times after harvest. Portions of 1-MCP-treated apples were also treated with ethylene in order to study the interaction between 1-MCP and ethylene. In other experiments, fruits were treated with ethylene first and then treated again with 1-MCP. Major results are as follows. Treatment of 1-MCP greatly retarded the senescence of `Tsugaru' apple stored at room temperatures as compared with the control. The sooner the time of 1-MCP treatment after harvest of fruit, the greater was the 1-MCP effect. In contrast to the time of 1-MCP treatment, the concentration of 1-MCP and duration of 1-MCP infiltration in a closed chamber exhibited only a minor effect. Ethylene treatment immediately before and/or after the 1-MCP treatment showed only the 1-MCP effect, thus clearly showing that 1-MCP treatment could completely reverse or counter the ethylene effect in `Fuji' apples. Repeated treatments of 1-MCP after a certain period of low temperature storage of `Fuji' apples were more effective than a single treatment. Parameters related with fruit quality will be discussed in detail.

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Late-harvested apple fruit generally are less responsive to 1-MCP than early harvested fruit, but the effect of harvest date on these responses can vary greatly by cultivar. Little is known about the relationships between internal ethylene concentration (IEC) and responses of fruit to 1-MCP. We have investigated the effects of 1-MCP on `McIntosh', `Cortland', and `Empire' apples in two experiments. In the first, fruit of each cultivar were picked three to five times during the normal harvest season, untreated or treated with 1 μL·L-1 1-MCP, and stored in air. Fruit IEC and firmness were then measured at monthly intervals for 4 months. In the second experiment, fruit were harvested several times during maturation, and, at each harvest, fruit were categorized into groups based on their IEC (<0.5, 0.5–1.0, 1–10, 10–50, 50–100; and >100 μL·L-1), treated with 1 μL·L-1 1-MCP for 24 hours at room temperature, and stored in air. The IEC and firmness of each fruit was then measured at set intervals during storage. Increasing IECs were associated with declining effectiveness of 1-MCP, but the individual fruit study showed that, even in high-IEC fruit, there was an initial inhibition of IEC values during storage before the IECs increased. A Lower IEC at harvest indicated a longer delay before the IEC ultimately increased. Collectively, the data show that it should be possible to determine the response of fruit to 1-MCP based on their IEC.

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Being self-incompatible, most Asian plums should be planted with a compatible pollinizer to produce fruits. Therefore, the selection of an adequate pollinizer is essential when new plum cultivars are released. To select a suitable pollinizer for ‘Summer Fantasia’ plum, the S genotype, cross-compatibility, pollen viability, and flowering time of five candidate cultivars were evaluated. Using polymerase chain reaction (PCR) analysis, the S genotype of ‘Summer Fantasia’ was determined as S a S c , which was expected to be compatible with other S genotypes. To test cross-compatibility, the trees were covered with caging net to prevent unintended pollination, and pistils were hand pollinated without emasculation. Fruit set percentage was calculated 10 weeks after pollination. The fruit set percentage resulting from the cross between ‘Summer Fantasia’ and ‘Taiyo’ (S b S c ) was 13.8%, whereas that resulting from other combinations was less than 5.0%. Pollen germination percentage was investigated to monitor pollen viability; it varied yearly among cultivars, although ‘Formosa’ (10.6%) and ‘Taiyo’ (13.8%) showed the highest pollen germination percentages among the cultivars. When averaged over three years and two locations, ‘Summer Fantasia’ bloomed 2–3 days after ‘Akihime’, ‘Formosa’, ‘Oishiwase’, and ‘Purple Queen’. Blooming period of ‘Summer Fantasia’ and ‘Taiyo’ overlapped almost entirely. Overall, the results indicated that ‘Taiyo’ was the most suitable pollinizer for ‘Summer Fantasia’.

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