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Wol-Soo Kim* and Jung-An Jo

This study was carried out to observe the effects of the pruning strength and the growth regulator on shoot growth and fruit shape in Pyrus pyrifolia cv. Niitaka. GA paste (GA) was known as a promoter of malformed fruits, but Mepiquat as an inhibitor. Light pruning treatment, of which removed the half of lateral shoots, decreased leaf area, weight, thickness, and the length of shoots and internodes in comparison to severe pruning. The occurrence of calyx perpetual fruit (CPF) in fruitlet stage was higher about 45% in severe pruning than in light pruning. Light pruning decreased malformed fruit by 10% compared to severe pruning at harvest stage, but there was no difference in soluble solid content of fruits between two treatments. Also light pruning decreased fruit weight. GA paste treatment on 50 days after full bloom significantly increased fruit weight, but Mepiquat decreased. In treatment of Mepiquat and GA the occurrence of malformed fruit was 31.3% and 35%, respectively and the index of symmetry was higher than control. Therefore, these results suggested that the light pruning has a positive effect on the production of symmetry fruit.

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Wol-Soo Kim and Jung-An Jo

Many trials to supply germanium to fruit have been carried out since tests have confirmed germanium's role as a medical substance. Supplying germanium in orchards by soil and foliar application was not effective because of loss from rainfall. In order to increase germanium absorption by fruit, this study carried out tree trunk injections during the growing season. Two types of germanium, GeO (inorganic type) and Ge-132 (organic type), in concentrations of 5, 10, 25, and 50 mg·L–1 were supplied to `Niitaka' pear trees by trunk injection (1.5 L/tree), four times at 15-day intervals from June 2004. The treatment with 50 mg·L–1 GeO showed decreased fruit weight, but 50 mg·L–1 Ge-132 showed no difference to the control and other treatments. Fruit lenticels were increased in size by all of the Ge treatments in comparison to control fruit. Soluble solids as well as Hunter value `a' of the fruits of all Ge treatments were higher than that of the control. Flesh browning after peeling the fruit was delayed by the germanium treatment, and polyphenoloxidase (PPO) activities were lowered. Postharvest potentials were maintained at high levels for fruit firmness, physiological disorders, and decayed fruit during cold storage at 0 to 1 °C for 2 months.

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Wol-Soo Kim* and Jung-An Jo

Although fruits obtained by organic cultivation (OC) have been believed to be healthier than those by conventional cultivation (CC), but clear experimental evidences supporting the assumption are still lacking. Therefore this study was carried out to investigate the effects of OC on total polyphenol content and anti-oxidant activity in `Hongro' apples (Malus domestica). Anthocyanin content of fruit skin was increased in apples from OC. Soluble solid content and pH of apple juice was higher in the OC than in the CC, but total acidity in fruit juice showed reversed result. Also, chlorophyll content showed no difference between OC and CC. Total polyphenol compounds extracted with methanol, were higher in the OC than in the CC, and also higher in peel than in flesh. Also, anti-oxidant activity estimated by free radical scavenging effect showed significantly stronger under the OC than the CC.

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Wol-Soo Kim and Jung-An Jo

Pear (Pyrus pyrifolia) fruits of `Whangkeumbae' were produced from the organic orchard at Yongam, southwestern Korea, which was managed by spraying with chitin incubated solution (CIS) 15 times from petal fall stage, mid-April to late August, to control pests and diseases during the growing season. The CIS contained about 50 kinds of chitin digestive and/or effective microorganisms and other organic/inorganic biologically active substances by incubating the mixtures at 30 °C for 7 days. The soil had standard levels of chemical and physical properties in Korea, as well as 3.0% to 4.0% organic matter. The organic fruits showed higher soluble solid contents, and fruit firmness was increased in comparison to conventional fruits. The organic fruit skin changed in color from yellow to brown, and black spot occurred; however, there was no difference in flesh tissues in terms of colors and textures. The phenolic compounds were significantly increased in organic fruits and leaves, with especially higher levels for fruit skin than for flesh tissues. Free radical levels dropped sharply in organic fruit, but slowly in conventional fruits. The results showed that the organic pear fruits have higher levels of antioxidant activity, and also showed the phenomena related to the change in fruit skin color from yellow to brown.

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Wol-Soo Kim, Jung-An Jo, and Soon-Ju Chung

Many trials to supply selenium to fruit have been carried out since tests have confirmed selenium's role as a medical substance. Supplying selenium in orchards by soil and foliar application was not effective because of loss from rainfall. In order to increase selenium absorption by fruit, this study carried out tree trunk injections during the growing season. Selenium solutions in concentrations of 5, 10, 25, and 50 mg·L–1 were supplied to `Niitaka' pear (Pyruspyrifolia) trees by trunk injection (1.5 L/tree) four times at 15-day intervals from June 2004.

The treatment with 50 mg·L–1 selenium showed necrosis symptoms at leaf-margins after secondary treatment and toxicity as abnormally red fruit skin color. Fruit weight and leaf area were decreased by selenium treatments, while severe symptoms appeared with higher selenium concentrations. Hunter values `a' and `b' in fruit skin color were increased by selenium treatment in comparison to the control. The selenium treatment showed lower soluble solids by as much as 1.2%, and higher fruit firmness. Selenium concentration in pear fruit was increased by trunk injection with a 5 mg·L–1 solution. The bound selenium in pear fruit after 3 months of storage in cold room conditions was very high, but free selenium was low.

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Wol-Soo Kim, Jung-An Jo, Soon-Ju Chung, Kil-Yong Kim, and Hyun Sug Choi

The shells of crab, shrimp, beetles, etc., could be decomposed by chitinase to chitin, calcium, and protein, respectively. We incubated the mixture solution of 1.5 kg crab shell, 1.5 kg multinutrient, 2 kg compost with microorganisms to decompose the chitin substance, 3 kg sugar, and 700 L water at room temperature for 7 days. During the incubation, aeration with an air pump was essential. We sprayed the chitin-incubated solution (CIS) after filtering to `Niitaka' pear (Pyrus pyrifolia) trees at 15-day intervals from May to Sept. 2004. Leaf area, leaf thickness, leaf specific weight, and chlorophyll contents were increased by the treatment with CIS. In fruit characteristics, fruit weight, soluble solids, fruit firmness, and Hunter values “a” and “b”were increased by the CIS treatment. Flesh browning after peeling the fruit was delayed by the CIS treatment, and polyphenoloxidase (PPO) activities were lowered.