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Jae-Chang Lee, Yong-Su Hwang and Ki-Youl Kim

Fruit maturity was hastened by 5 to 7 days with the application of GA3 and GA4+7 paste on petioles 4 weeks after full bloom and 3 to 4 days with the spray of both ethephon (1,000ppm) and dichroprop(30ppm) 62 days after full bloom. Fruit size was significantly increased by GAs treatment but there was a tendency of decreasing fruit size by ethephon and dichroprop treatments. Excessive softening of flesh was found in ethephon or dichroprop treated fruits while no significant difference was observed with GAs treatment until maturity. Calcium acetate partially prevented the enhancement of fruit softening and fruit size decrease induced by ethephon and dichroprop. Other fruit qualities such as soluble solids contents were not affected by the addition of calcium acetate except some delay in fruit maturity.

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Yong-Soo Hwang, Jong-Pil Chun and Jae-Chang Lee

Physiological disorder occurred in a recently developed oriental melon cultivar, `Gumssaragi-Bunchun' (Cucumis melo var. makuwa), is involved with the appearance of water soaking area in placenta and can be extended to the pulp when severely affected. Physiological changes between normal and disordered fruits were compared. Ethanol soluble sugars were significantly decreased in both pulp and placenta tissue of disordered fruits whereas acidity was increased. Ethanol and acetaldehyde accumulation were confirmed in juice from disordered fruits, which were net detectable in normal ones. The contents of boron and calcium, especially water and HCl soluble calcium, were fairly low in disordered pulp. Also, there was a great difference in pectin content between both fruit tissue and severe hydrolysis of water soluble pectins isolated from disordered placenta was found by gel chromatography. However, the hydrolysis of pectins seemed not to be associated with the increase of wall hydrolase activities such as polygalacturonase and β-galactosidase.

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Jong-Pil Chun, Jae-Chang Lee and Yong-Soo Hwang

Pectins isolated from three cultivars with different maturity were compared to find a potential role of pectin modification on the fruit softening during fruit development and ripening. There was an increase of total pectins in developing fruit and no significant decrease of pectins was confirmed even after storage in `Tusgaru' (30 days) and `Fuji' (120 days), whereas soluble pectins, except NaOH-soluble ones, gradually increased in all cultivars. Gel-filtration profile and ion exchange chromatographic evidence of soluble pectins revealed that pectin degradation in apple fruit may not be associated with softening. However, a degree of esterification probably has an important role on softening of fruits. Further results will be discussed in the presentation.