Kwang-Sik Cho

Frostfall Forecasting in the Naju Pear Production Area Based on Discriminant Analysis of Climatic Data

In order to predict frostfall, nocturnal cooling rate and air temperature changes were analyzed on days with and without frost when the maximum temperature was lower than . In general, the nocturnal cooling rates on frosty days were higher than those on non-frosty days. The cooling rates averaged from 19:00 to 24:00 on frosty and non-frosty days were and respectively. As expected, the nocturnal temperature on frosty days was lower than that on non-frosty days. Especially, the midnight air temperature averaged about on frosty days, which was lower than that on non-frosty days (i.e., ). The discriminant analysis using three independent variables (i.e., total cloud amount, air temperature at 24:00, and 5-day rainfall amount) successfully classified the presence of frost with 87% accuracy.

Foliar applications of urea and a potent growth regulator ameliorate calyx-end cracking in persimmon.

Department of Horticulture, College of Agriculture and Life Sciences, Gyeongsang National University, Jinju 52828, Korea Institute of Agriculture and Life Science, Gyeongsang National University, Jinju 52828, Korea Pear Research Institute, National Institute of Horticultural and Herbal Science, Rural Development Administration, Naju 58216, Korea Central Instrument Facility, Gyeongsang National University, Jinju 52828, Korea Department of Biology Education, College of Education, Gyeongsang National University, Jinju 52828, Korea

Breeding of ‘Joyskin’ Pear as fruit for Eating withthe Skin

In 1994, a new cultivar ‘Joyskin’ was created from a cross between the cultivars ‘Whangkeumbae’ and ‘Waseaka’ at the Pear Research Institute of the National Institute of Horticultural and Herbal Science, Rural Development Administration. In 2006, the ‘Joyskin’ was selected from among the 317 seedlings resulting from the cross for its skin and taste qualities. Regional adaptation tests were conducted in nine regions and in ten experimental plots from 2006 to 2011. The cultivar was named in 2011. ‘Joyskin’ showed a vigorous growth habit and semi-spread characteristics similar to ‘Whangkeumbae’. The average full bloom date for ‘Joyskin’ was April 21st, which was also similar to ‘Whangkeumbae’. The optimum fruit ripening time was September 6-8th, which was six or eight days earlier than ‘Whangkeumbae’. The fruit was round in shape and the skin was a golden yellow color at maturity. The average fruit weight was 320 g and the flesh firmness was 2.5 kg/8mmφ. The firmness of the fruit skin determined by a blade-type plunger of texture analyzer was 22.9 N, which was significantly different from that of ‘Whangkeumbae’ 29.9N. Stone cell analysis of ‘Joyskin’ by phloroglucinol-HCl, showed that ‘Joyskin’ stone cells were small in size and few in numbers cpmpared to those of cultivars of was ‘Manpungbae’, ‘Niitaka’, and ‘Whangkeumbae’. The patent application for ‘Joyskin’ was submitted in April, 2012 (Grant No. 2012-337). In 2016, ‘Joyskin’ (Grant No. 5895) was registered as a separate record, with uniformity and stability per Korean Seed Industry Law. Additional key words: crossing breeding, fruit, Pyrus pyrifolia, self-incompatibility, stone cell

Effect of Various Pear Cultivars at Different Fruit Development Stages on Antioxidant and Whitening Activities

This study was carried out to investigate the total polyphenols, antioxidant activities, and melanin synthesis inhibition of several pear cultivars (Pyruspyrifolia). The total polypenolic content of five pear cultivars was high in the unripe developmental stage. Total polyphenolic content of the Chuwhangbae cultivar extract was higher than that of other pear cultivars regardless of the developmental stage. However, the total flavonoid content did not differ between cultivars or developmental stages. The phenolic compound, arbutin has an inhibitory effect on melanogenesis. Arbutin levels in pear cultivars declined as the fruit matured. The free radical scavenging activity of the extract also decreased as the fruit ripened. In B16F10 mouse melanoma cells, most of the cultivar extracts inhibited melanin synthesis by about 50% at a 100 μg·mL −1 concentration, except in the Gamcheonbae extract until 90 days after full bloom. We have confirmed that the extract of pear cultivars have antioxidant activity and skin-whitening effects.