Variation of Bio-active Substance of Major Soybean Cultivars by Different Sowing Time in Southern Korea

The purpose of this study was to investigate the effects of sowing time on the bio-active content of major soybean cultivars in a southern region of South Korea. Experiments were carried out in Naju, Jeonnam Province (latitude 35° 04'N, longitude 126° 54'E) from 2008 to 2010. The cultivars grown in summer included Saeol- kong and Tawon-kong and those grown in autumn included Taekwang-kong, Pungsannamul-kong, and Cheongja3, respectively. Sowing dates were May 15 and 30, June 15 and 30, and July 15 of each year. Daidzein content was increased in all the test cultivars grown from later sowing, and the contents of genistein and total isoflavone were increased in all the test cultivars except for Cheongja3. On the other hand, glycitein content showed no significant change in any of the test cultivars across the 5 sowing dates except for Tawon-kong. Cyanidin-3-glucoside (C3G) content was significantly increased in Tawon-kong and Cheongja3, and delphinidin-3-glucoside (D3G) and total anthocyanin contents were significantly increased in Tawon- kong. However, pelargonidin-3-glucoside (Pg3G) and petunidin- 3-glucoside (Pt3G) contents showed no significant difference in plants sown across the 5 dates. Lutein content in Cheongja3 was between 2.7 and 3.0 µg/g based on sowing date and did not vary significantly, while chlorophyll content increased with later sowing and was significantly higher in the cultivars sown on June 30 and July 15. Crude fat content was higher in Taekwang-kong and Cheongja3 when the cultivars were sown earlier; crude fat did not vary in the other test cultivars based on sowing date. Palmitic acid composition was not affected by sowing date in most of the test cultivars. Stearic acid was increased in Saeol-kong, Tawon-kong, and Cheongja3 with later sowing. Oleic acid and linoleic acid were significantly higher in Saeol-kong at an earlier sowing date. The composition of linolenic acid showed significantly increased dates in most of the test cultivars with later sowing. There were no significant differences in carbohydrate and crude protein content across 5 different sowing dates in most of the test cultivars. However, crude protein content was higher in Saeol-kong when sowing occurred earlier, and was higher in Tawon-kong at later sowing dates. Keywords : bio-active substance, sowing time, soybean, variation