‘Godangok1’, a sweet corn hybrid obtained by crossing the inbred KSE13 (female) and KSE37 (male), was developed by the maize breeding team at the National Institute of Crop Science (NICS), Rural Development Administration, Korea, in 2016. ‘Godangok1’ has the sugary enhancer (se) gene, and the ear is yellow-white. The number of days to silking of ‘Godangok1’ was 59, similar to ‘Danok3’ (check variety), but ear length and the ratio of kernel set length to ear length (18.7 cm and 96%, respectively) were superior to those of ‘Danok3’. The resistance to Bipolaris maydis, Exserohilum turcicum, and Ostrinia furnacalis was similar to that exhibited by ‘Danok3’, whereas the lodging tolerance was stronger than that of ‘Danok3’. The fresh ear yield of ‘Godangok1’ was 6,530 ears, with 1,139 kg per 10a, and the sugar content was 20.8 °Brix. The hundred kernel weight was 27.4 g, smaller than that of ‘Danok3’. The flavor was excellent and assigned a sensory score of 5.7. Unique properties of ‘Godangok1’ coded by the recessive se gene are eliminated due to crosspollination when growing along with other types of corn such as general corn (sh, sh2, bt, etc.). Therefore, it must be isolated in time or space and harvested in order to produce high-quality sweet corn (Registration No. 7506).

Baekgeumok, a sweet corn hybrid made by crossing inbred KSE15 and KSE21, was developed by the maize breeding team at the National Institute of Crop Science, Rural Development Administration in 2015. Baekgeumok silks at 63 days, similar to Danok3 (check variety). The plant height is 179 cm, higher than check variety, and the ear height is 105 cm, similar to check variety. Baekgeumok has an excellent lodging resistance. The fresh ear yields were 6,411 ears and 1,141 kg in 10 a. Pericarp thickness was 39 µm and sugar content was 19.5 °Bx. Sensory evaluation value was 6.1 and flavor was excellent. This hybrid can be cultivated in Gyeonggi-do, Gangwon-do, Chungcheongbuk-do, Gyeongsangbuk-do, and Gyeongsangnam-do. Seeds of Baekgeumok must be renewed annually, because this hybrid is a single cross hybrid. This sweet corn hybrid must be cultivated at least 200 m from areas with other corn varieties, because of their recessive gene. When cultivated at high density, the ear size and ratio of kernel set length / ear length will be lower in this hybrid than in standard cultivars. This hybrid requires pest control because it is susceptible to corn borer infestation. Drainage management is important in the rainy season. (Registration No. 6725)

‘KM1’, a corn hybrid was developed for seed export to Southeast Asia by the maize breeding team of the National Institute of Crop Science (NICS), RDA in 2016. The hybrid ‘KM1’ was obtained by crossing two inbred lines, ‘KS155’ and ‘15VL060’. After yield trials at Dong Trieu, Vietnam for one year, country adaptability trials were subsequently carried out in three countries (Vietnam, Cambodia, and Indonesia) in 2016. ‘KM1’ is a white-yellow and dent-like corn, and the plant adapts to the northern part of Vietnam and northwestern part of Cambodia; and the corn can be used as food and feed. The plant is fast flowering and has strong lodging tolerance and resistance to southern leaf blight and downy mildew. Silking date of ‘KM1’ is 5 days earlier than that of Vietnam’s leading cultivar ‘LVN10’. The grain yield of ‘KM1’ is 879 kg/10a in Vietnam, which is 22% higher than that of LVN10, and 914 kg/10a in Cambodia, which is 5% higher than that of Cambodia’s leading cultivar ‘CP888’. This hybrid requires the implementation of disease control measures because it is susceptible to corn rust. (Registration No. 7507).

This study was conducted to compare changes of total carotenoid contents and antioxidant activities in yellow waxy corns (Zea mays L.) depending on harvest time. The total carotenoid contents of yellow waxy inbred lines and hybrids increased from 19 days and then the highest content of total carotenoid contents was observed at 25 to 27 days after pollination. Thereafter, there was little change in total carotenoid contents. According to analysis total content of carotenoids on 23 days after pollination, which was the period of harvesting waxy corn, KY2 was the highest as 15.4 ㎍/g in inbred lines and KY2/KY39 was the hightest as 11.2 ㎍/g in hybrids, respectively. The total carotenoid contents of each hybrid were higher than mean that of their parent lines except for some hybrids. The total carotenoid contents of KY27/KY37 were significantly higher than those of their parental lines. Antioxidant activity of yellow waxy corn showed a tendency to increase after decrease depending on delaying harvesting time. Antioxidant activities of hybrids were higher than that of inbred lines. As a result of correlation analysis between total carotenoid contents and antioxidant activity, correlation coefficient of inbred lines and hybrids was as low as -0.12 and -0.13, respectively. When the harvest time was delayed, the lightness of yellow waxy corn decreased but the redness and yellowness increased. As a result of correlation analysis between Hunter’s Lab value and total carotenoid contents, correlation coefficient of lightness, redness and yellowness were -0.22, 0.67, 0.53, respectively.