‘Alchanheukchal’ is a single-cross hybrid waxy corn cultivar developed by using the inbred line ‘KBW16’ as the seed parent and ‘KBW23’ as the pollen parent. Yield trials were conducted in 2013 and 2015 followed by regional adaptability tests at six locations over three years (2018-2020). Recognized for its superior performance, it was designated as a new variety by the NICS in 2020. ‘Alchanheukchal’ contains 32.9 μg 100 g^-1 of anthocyanins, resulting in black-colored ears and exhibiting an intermediate ear shape. Its silking period was 74 days, equivalent to that of the standard variety ‘Ilmichal’. The ear length was 19.3 cm, similar to ‘Ilmichal’, while the kernel set rate was 94%, which was lower than that of ‘Ilmichal’. In terms of disease and pest resistance, including southern rust, northern corn leaf blight, and corn borer, as well as lodging resistance, ‘Alchanheukchal’ was comparable to ‘Ilmichal’. The number of ears and ear weight per 10a were 6,336 ears and 1,136 kg, respectively, which indicates a higher ear number but lower ear weight than ‘Ilmichal’. The 100-kernel weight was 27.7 g, smaller than that of ‘Ilmichal’. In sensory evaluation tests, the overall acceptability score was 4.7, which was lower than that of ‘Ilmichal’. The highest seed production efficiency was observed when the planting ratio of the seed parent to pollen parent was 2:1. However, because the silking date of the pollen parent occurred later, it was considered necessary to perform staggered sowing (Registration No. 10033).

‘Godangok 2’, a yellow sweet corn hybrid obtained by crossing inbred KSE14 (female) and KSE23 (male) varieties harboring the sugary enhancer (se) gene, was developed by the maize breeding team at the National Institute of Crop Science (NICS), Rural Development Administration, Korea, in 2020. Days to silking of ‘Godangok 2’ (65 days) was 3 days later than ‘Danok 3’ (check hybrid, 62 days). The ear length of ‘Godangok 2’ (18.9 cm) was similar to that of ‘Danok 3’, but it exhibited a higher kernel filling rate (97%). In addition, the lodging tolerance of ‘Godangok2’ was greater than that of ‘Danok3’. The number of ears per 10a in Godangok2 (6,177) was 4% higher than that in ‘Danok 3’, whereas ear weights (1,075 kg) were 4% lower. ‘Godangok 2’ had a high sugar content of 23.4° Brix, a thin pericarp thickness of 21.4 μm, and a light 100-kernel weight of 25.4 g compared to that of the check hybrid. ‘Godangok 2’ showed the highest seed yield of 270 kg/10a at a 4 (female):1 (male) planting ratio. Because ‘Godangok 2’ carries the recessive se gene, its unique qualities may be compromised by cross-pollination with other corn varieties (e.g., sh2, bt, wx types). Therefore, to maintain sweet corn quality, corn should be grown and harvested separately in time and space (Registration No. 10059).

‘KM7’, a maize hybrid for grain production, was developed for the Southeast Asian seed market by the maize breeding team of the National Institute of Crop Science (NICS), Rural Development Administration (RDA) in 2020. The hybrid, ‘KM7’, was bred by crossing two inbred lines, CL32 and 14K23. After a one-year yield trial in Dong Trieu, Vietnam, country adaptability trials were performed three times in three different countries (Vietnam, Cambodia, and Indonesia) in both 2019 and 2020. The seed type was flint-like and suitable for both food and feed. ‘KM7’ adapted well to conditions in northern Vietnam, northwestern Cambodia, and Central Java in Indonesia. The silking date of ‘KM7’ in Vietnam was 62 d, which was 1 d earler than that of LCH9, a leading cultivar in Vietnam. ‘KM7’ is an early maturing, high-grain yielding F1 hybrid that is also resistant to downy mildew. ‘KM7’ produced a grain yield of 842, 831, and 950 kg/10a in Vietnam, Cambodia, and Indonesia, respectively. This demonstrated a higher yield than that of the leading cultivars in each respective country. ‘KM7’ produced 26% more grain in Vietnam, 28% more in Cambodia, and 56% more in Indonesia than the respective control varieties (Registration No. 10034).

‘Sinhwangok2’ is a single cross maize F₁ hybrid (Zea mays L.) that was developed by the maize breeding team at the National Institute of Crop Science (NICS), RDA, in 2018. This yellow high-yielding intermediate maize hybrid was obtained by crossing between two inbred lines― KS214 and KS215. After advanced yield trials over two years in Suwon, a regional yield trial for ‘Sinhwangok2’ was conducted to evaluate its growth and yield at three different locations, from 2016 to 2018. ‘Sinhwangok2’ requires 72 days for silking and its plant height is 243 cm, similar to that of ‘Jangdaok’; its ear height ratio is 49%, like that of ‘Jangdaok’, and the hybrid shows resistance to lodging. The number of ears per 100 plants was found to be 100 and the ear length of ‘Sinhwangok2’ is 19.5 cm, which is shorter than that of ‘Jangdaok’. The weight of 100 seeds of ‘Sinhwangok2’ is 30.8 g, similar to that of ‘Jangdaok’. This hybrid shows moderate resistance to southern leaf blight (Bipolaris maydis). It has moderate resistance to European Corn Borer (Ostrinia nubilalis). The grain yield (i.e., 9.41 ton/ha) of ‘Sinhwangok2’ was found to be 13%, which is higher than that of ‘Jangdaok’. Seed production of ‘Sinhwangok2’ was 2.36 ton/ha and was considered acceptable due to a good synchronization of flowering period during crossing between the seed parent, KS214, and the pollen parent, i.e., KS215, in Yeongwol and F₁ seed yield. ‘Sinhwangok2’ can thus be a suitable cultivar for all plain areas in Korea and can possibly be cultivated via double cropping with winter forage crop because of their early maturity. (Registration No. 8963).

‘KM2’, a maize hybrid grain was developed for the Southeast Asian seed market by the maize breeding team of the Rural Development Administration (RDA), South Korea 2018. ‘KM2’ was bred by crossing two inbred lines, ‘15VL065’ and ‘KS155’. After a advanced yield trial at Dong Trieu, Vietnam, for the first cropping cycle in 2016, country adaptability trials were performed twice in three different countries: Vietnam, Cambodia, and Indonesia, in 2016 and 2017. ‘KM2’, a yellow intermediate seed for food and feed, adapts well to the northern Vietnam, northwestern Cambodia, and Central Java in Indonesia. It is an early maturing high-grain yield F1 hybrid. This hybrid is resistant to downy mildew, but not corn rust. The silking date of ‘KM2’ is 10 days earlier than that of ‘LVN10’, a leading cultivar in Vietnam. ‘KM2’ produced grain yields of 811 kg/10a, 845 kg/10a, and 783 kg/10a in Vietnam, Cambodia, and Indonesia, respectively, showing even higher grain yield than the countries’ respective leading cultivar. ‘KM2’ produced 61%, 17%, and 14% higher grain yield in Vietnam, Cambodia, and Indonesia, respectively, than their respective control cultivars (‘LVN10’, ‘CP888’, ‘P21’) (Registration No. 8192).

‘Hwanggeummatchal’, a yellow waxy corn hybrid obtained by crossing inbred ‘KY37’ and ‘KY29’, was developed by the maize breeding team at the National Institute of Crop Science (NICS), RDA, Korea, in 2017. The number of days to silking of ‘Hwanggeummatchal’ was 69 days after planting, 2 days earlier than ‘Ilmichal’ (a control variety). Plant height of ‘Hwanggeummatchal’ was 205 cm, lower than that of the control, and ear height ratio was 49%, which was lower than that of ‘Ilmichal’. Lodging resistance of ‘Hwanggeummatchal’ was similar to ‘Ilmichal’. The fresh ear yields were 6,389 ears in 10 a. The carotenoid content of ‘Hwanggeummatchal’ was 16.4 μg 100 g^-1 fresh weight, which was much higher than that of ‘Ilmichal’. The pericarp thickness was 41 μm. The sensory evaluation value was 5.7, and the flavor was excellent. The flowering period of its parental lines was well matched, and seed production was best at a planting ratio of maternal and paternal lines, 3:1. ‘Hwanggeummatchal’ is suitable to the whole country, except for Jeju-do. Seeds of ‘Hwanggeummatchal’ must be renewed annually because it is a single cross hybrid. If this hybrid is cultivated under high-density conditions, the ear size and the ratio of kernel set length to ear length will be lower than that of standard cultivation. Pest control should be performed for this hybrid because it is susceptible to corn borer (Registration No. 8136).

‘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).

‘Hwangdaok’, a new maize F1 hybrid (Zea mays L.), was developed by the maize breeding team at the National Institute of Crop Science (NICS), RDA in 2016. The high-yielding yellow dent hybrid named ‘Hwangdaok’ was obtained by crossing between two inbred lines, ‘KS203’ and ‘KS190’. After advanced yield trial in Suwon in 2012, regional yield trial was subsequently carried out to evaluate the growth and yield of ‘Hwangdaok’ at three different locations from 2014 to 2016. The number of days to silking of ‘Hwangdaok’ is 76. The plant height is 262 cm and ear height ratio is 51%, which are similar to those of ‘Jangdaok’. It has resistance to lodging. The number of ears per 100 plants is 95. The ear length is 21.3 cm and weight of 100 seeds is 34.7 g, similar to those of ‘Jangdaok’. It has moderate resistance to southern leaf blight (Bipolaris maydis) and European corn borer (Ostrinia nubilalis). The grain yield (10 ton/ha) of ‘Hwangdaok’ is 6% higher than that of ‘Jangdaok’. The seed production rate of ‘Hwangdaok’ is acceptable due to good synchronization of flowering period during crossing between the seed parent, KS203, and the pollen parent, KS190, in Yeongwol. F1 seed yield was 1.68 ton/ha. ‘Hwangdaok’ can be a suitable cultivar to plain areas in Korea. (Variety registration No. 7502).

‘Dacheongok’, a new maize F₁ hybrid (Zea mays L.), is developed by the maize breeding team at the National Institute of Crop Science (NICS), RDA in 2016. The high-yielding hybrid, named ‘Dacheongok’ was bred by crossing between two inbred lines, ‘KS197’ and ‘KS202’. It is a yellow dent maize hybrid. After advanced yield trial of ‘Dacheongok’ in Suwon for one year, regional yield trial was subsequently carried out for evaluation of its growth and yield at four different locations from 2014 to 2016. The days to silking of ‘Dacheongok’ are 80, similar to ‘Kwangpyeongok’. The plant height of ‘Dacheongok’ is 267 cm, similar to ‘Kwangpyeongok’, and its ear height ratio is 51%, similar with that of ‘Kwangpyeongok’. It has resistance to lodging. The stay-green of ‘Dacheongok’ is not different with that of ‘Kwangpyeongok’. The number of ear per 100 plants of ‘Dacheongok’ is 95, similar to ‘Kwangpyeongok’. The ear length of ‘Dacheongok’ is 18.6 cm, longer than that of ‘Kwangpyeongok’. The weight of 100 seeds of ‘Dacheongok’ is 29.8 g, similar to that of ‘Kwangpyeongok’. It has moderate resistance to southern leaf blight (Bipolaris maydis). It has moderate resistance to European Corn Borer (Ostrinia nubilalis). The dry matter yield (23.69 ton/ha) of ‘Dacheongok’ was 10% higher than that of ‘Kwangpyeongok’. The TDN (Total Digestible Nutrients) yield (16.11 ton/ha) of ‘Dacheongok’ was 7% higher than that of ‘Kwangpyeongok’. The seed production of ‘Dacheongok’ was acceptable due to a good synchronization of flowering period during crossing between the seed parent, KS197, and the pollen parent, KS202, in Yeongwol and F₁ seed yield was 2.46 ton/ha. ‘Dacheongok’ would be a suitable cultivar to all plain area in Korea. (Variety registration No. 7054)

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.

‘Sinhwangok’, a new maize F₁ hybrid (Zea mays L.), is developed by the maize breeding team at the National Institute of Crop Science (NICS), RDA in 2015. The high-yielding hybrid, named ‘Sinhwangok’ was bred by crossing between two inbred lines, ‘KS178’ and ‘KS145’. It is a yellow dent maize hybrid. After advanced yield trial of ‘Sinhwangok’ in Suwon for two years, regional yield trial was subsequently carried out for evaluation of its growth and yield at three different locations from 2012 to 2015. The days to silking of ‘Sinhwangok’ are 74. The plant height of ‘Sinhwangok’ is 241cm, similar to ‘Jangdaok’, and its ear height ratio is 51%, similar with that of ‘Jangdaok’. It has resistance to lodging. The number of ear per 100 plants is 96. The ear length of ‘Sinhwangok’ is 17cm, shorter than that of ‘Jangdaok’. The weight of 100 seeds of ‘Sinhwangok’ is 34.1g, similar to that of ‘Jangdaok’. It has moderate resistance to southern leaf blight (Bipolaris maydis). It has moderate resistance to European Corn Borer (Ostrinia nubilalis). The grain yield (8.9 ton/ha) of ‘Sinhwangok’ was 15% higher than that of ‘Jangdaok’. The seed production of ‘Sinhwangok’ was acceptable due to a good synchronization of flowering period during crossing between the seed parent, KS178, and the pollen parent, KS145, in Yeongwol and F₁ seed yield was 2.3 ton/ha. ‘Sinhwangok’ would be a suitable cultivar to all plain area in Korea.

‘Daanok’, a new maize F₁ hybrid (Zea mays L.), is developed by the maize breeding team at the National Institute of Crop Science (NICS), RDA in 2013. The high-yielding hybrid, named ‘Daanok’ was bred by crossing between two inbred lines, ‘KS174’ and ‘KS175’. It is a yellow semi-flint maize hybrid (Zea mays L.). After preliminary yield trial and advanced yield trial of Daanok in Suwon for two years, regional yield trial of that was subsequently carried out for evaluation of its growth and yield at three different locations from 2011 to 2013. The silking date of Daanok is earlier than that of the check hybrid, ‘Jangdaok’. The plant height of Daanok is 229cm, similar to Jangdaok, and its ear height ratio is similar with that of Jangdaok.It has resistance to lodging. There are much of the No. of ear per 100 plants. The ear length of Daanok is similar with that of Jangdaok. The weight of 100 seeds of Daanok is the same with that of Jangdaok. It has strong resistance to northern leaf blight (Exserohilum turcicum) and southern leaf blight (Bipolaris maydis). It has strong resistance to ear lot. It has moderate resistance to corn borer. The grain yield (7.34 ton/ha) of Daanok was 23% higher than that of Jangdaok. The seed production of Daanok has gone well due to a good synchronization of flowering period during crossing between the seed parent, KS174, and the pollen parent, KS175, in Yeongwol and F1 seed yield was 2.38 ton/ha. Daanok would be a suitable cultivar to all plain area in Korea.

A ‘Hayanchal95’, a new waxy corn hybrid, is a single cross hybrid developed by the maize breeding team at the National Institute of Crop Science (NICS), Rural Development Administration(RDA) in 2011. This hybrid was made by crossing between seed parent KW44 and pollen parent KW35. Days to silking of Hayanchal95 was three days earlier than Ilmichal, a check hybrid. Ear length and diameter of Hayanchal95 were 18.3 cm and 4.1 cm, respectively. The ratio of kernel set length to ear length was 90% and lower than Ilmichal. Its quality characteristics like amylopectin content, hardness of kernels, and value of sensory evaluation were not significantly different from Ilmichal except grain length. Resistance to corn borer and lodging tolerance of Hayanchal95 were better than Ilmichal. The number of fresh ears was similar to those of Ilmichal and weight of fresh ears was lower than Ilmichal in regional yield trials (RYT) from 2009 to 2011. Although flowering time of its parent lines was good match during crossing between the seed and pollen parents, seed production was low. It is adaptable to the whole country. Plant variety protection right of ‘Hayanchal95’ was registered in July 2014, and its grant number is 5110.

‘Dapyeongok’, a new maize F₁ hybrid (Zea mays L.), is developed by the maize breeding team at the National Institute of Crop Science (NICS), RDA in 2010. The high-yielding hybrid, named ‘Dapyeongok’ was bred by crossing between two inbred lines, ‘KS158’ and ‘KS155’. It is a yellow dent maize hybrid (Zea mays L.). After preliminary yield trial and advanced yield trial of Dapyeongok in Suwon for two years, regional yield trial of that was subsequently carried out for evaluation of its growth and yield at three different locations from 2008 to 2010. The silking date of Dapyeongok is the same with that of the check hybrid, ‘Jangdaok’. The plant height of Dapyeongok is similar to Jangdaok, and its ear height ratio is the same with that of Jangdaok. It has resistance to lodging. The ear length of Dapyeongok is shorter than that of Jangdaok. The weight of 100 seeds of Dapyeongok is lighter than that of Jangdaok. It has strong resistance to northern leaf blight (Exserohilum turcicum) and southern leaf blight (Bipolaris maydis). It has moderate resistance to black streaked dwarf virus (BSDV), ear lot and corn borer. The grain yield (8.6 ton/ha) of Dapyeongok was 8% higher than that of Jangdaok. The seed production of Dapyeongok has gone well due to a good synchronization of flowering period during crossing between the seed parent, KS158, and the pollen parent, KS155, in Yeongwol and F₁ seed yield was 2.8 ton/ha. Dapyeongok would be a suitable cultivar to all plain area in Korea.

A single cross hybrid, ‘Godangok’, is a yellow sweet corn developed by the maize breeding team at the National Institute of Crop Science (NICS), Rural Development Administration (RDA) in 2011. This hybrid was produced by crossing between KSE5 and KSE19. KSE5 is a seed parent and KSE19 is a pollen parent of Godangok. Days to silking of Godangok was 3 days later than Danok 3, a check hybrid. Ear length and diameter of Godangok were 17.6 cm and 4.4 cm, respectively. The ratio of kernel set length to ear length was 87.1%. These characteristics of ear were similar to those of the check hybrid. However, the Degree Brix was 24.3 °Bx, higher than the check hybrid, 14.1 °Bx. Lodging tolerance of Godangok was better than the check hybrid. The number and weight of fresh ear of Godangok were similar to those of the check hybrid in regional yield trials (RYT) from 2009 to 2011. Seed production of this hybrid is good due to good match between the seed and pollen parent. It is adaptable to the whole country. Plant variety protection right of ‘Godangok’ was registered in July 2014, and its grant number is 5094.

Cheongdaok, a new single maize (Zea mays L.) variety, was developed by the maize breeding team at the National Institute of Crop Science (NICS), RDA in 2010. This high-yielding hybrid was produced by crossing two inbred lines, KS159 and KS155. KS159 is the seed parent and KS155 is the pollen parent of Cheongdaok. It is a yellow dent maize hybrid. After the preliminary yield trial and advanced yield trial of Cheongdaok in Suwon for two years, the regional yield trial was subsequently carried out for evaluation of its growth characteristics and yield at four different locations from 2008 to 2010. The silking date of Cheongdaok is one day earlier than that of the check hybrid, Kwangpyeongok. Compared to Kwangpyeongok, the Cheongdaok show short in plant height and low in ear height ratio. It has resistance to lodging. The stay-green degree and the ear ratio of Cheongdaok are similar to Kwangpyeongok. It has moderate resistance to southern leaf blight (Bipolaris maydis) and strong resistance to northern leaf blight (Exserohilum turcicum). It has moderate resistance to black streaked dwarf virus (BSDV), ear lot, and corn borer. The dry matter yield 20.24 ton/ha and the total digestible nutrient (TDN) yield (13.80 ton/ha) of Cheongdaok were similar to Kwangpyeongok. The grain yield (8.51 ton/ha) of Cheongdaok was higher than that of Jangdaok. The seed production of Cheongdaok was well processed due to a good synchronization of flowering period during crossing between the seed parent KS159 and the pollen parent KS155, and the F1 seed yield was 1.8 ton/ha in Yeongwol.