Sorghum is a rich source of various phytochemicals including phenolic compounds that have potential to significantly benefit human health. Phytochemical production may be induced not only by genotype but also by a number of environmental factors including temperature and an amount of sunshine. The objective of this study was to determine the effect of planting dates and harvesting stages on the quality traits of ‘Donganme,’ a grain sorghum variety developed to produce high antioxidants. ‘Donganme’ was planted in three locations on four dates from early May to early July. Each planted fraction was harvested 35, 40, 45, 50, and 55 days after the head shooting date, respectively. The results showed that significant differences existed between the growth period and content of polyphenol and flavonoid. The sorghum harvested at 35 days after head shooting had the higher polyphenol and flavonoid content in all planting times and the tannin content was increased as the planting date was delayed. So the sorghum grown in late planting dates (July 5) had highest polyphenol content (2.07 gGAE/100g) at early harvesting (35 days) while late planting gave the low grain yield (1.3 ton/ha). Polyphenol index to average temperature during 35 and 45 days after heading of ‘Donganme’ showed that total polyphenol contents were decreased by 5.2% and 4.4%, respectively, with increasing average temperature of 1oC. And high correlation (R=0.85) was observed between accumulated temperature and the amount of polyphenol of ‘Donganme’, confirming the major contribution of the quality traits is temperature. To produce high quality grain from sorghum the relation between the yield and nutrition components must be considered simultaneously (i.e., Sorghum produced the highest polyphenol and flavonoid when planted in June 15 and harvested at 40 to 45 days after head shooting .

In the past years, few grain sorghum varieties with limited yield potential have been developed and grown in Korea. Hybrids tend to be more productive and resistive to unfavorable environmental conditions than pure line varieties. However, no hybrid cultivars are available and never have been planted for grain sorghum in Korea. The main aims of this study were to (i) verify if US x Korean and US x US hybrids increase grain yield in Korea; (ii) assess the performance of waxy hybrids in Korea and the US; (iii) estimate general combining ability and specific combining ability for the lines studied; and (iv) identify superior lines and hybrids for future use in breeding. Two distinct sets of waxy-endosperm sorghum hybrids derived from Korean landraces and US lines (Texas A&M University) were tested in the US and Korea. Compared to the parental lines, hybrids derived from US lines and Korean landraces showed yield increase that ranged from 2% to 127%. Hybrids created from US lines showed higher heterosis than US x Korean hybrids. Hybrid vigor was observed in the US and Korea, but shifts in ranks of hybrid performance occurred. The results indicate that it is feasible to develop grain sorghum hybrids adapted to Korean conditions only if delibrate selections take place in Korea. A combination of Korean and US sources could provide an acceptable germplasm base for developing Korean landrace based sorghum hybrids.