No abstract

In Korea, native or open pollinated corn varieties that were not improved before 1960 were cultivated. The 1960s was a step that created the foundation for the development of varieties. In 1962, systematic corn breeding was started when the synthetic type 'Hwangok 2' was distributed to farmers. The 1970s was the era of the change from synthetic varieties to hybrid ones, with a focus on the development of single-cross hybrids among the corn hybrids. The single-cross corn hybrid, 'Suwon 19', was an epoch-marking variety that had a unit-yield closer to that of advanced countries. The 1980s was a time when the breeding direction was changed from grain corn to silage because the corn cultivation area for silage increased rapidly with the government's livestock promotion policy, and the corn seed supply system of single-cross hybrids was established. In the 1990s, the era of globalization and the launching of imports of agricultural products, the living standards of consumers became more advanced, and the development system of corn varieties was established for various use purposes. As we entered the 2000s, it started the heyday of developing corn varieties, with 29 corn varieties of various use purposes and excellent cultivation stability developed. In the 2010s, the scope of corn variety development expanded from government or universities to private seed companies. Thus, the corn varieties in Korea have changed and developed in response to the situation of the times, and there are currently 110 corn varieties registered with Korea Seed & Variety Service (KSVS). In the future, vegetable corn is expected to be continuously developed, with functional ingredients such as strengthening vitamins, trace elements, and antioxidant components. Specialized grain corn, such as lysine and maltodextrin, will be developed and commercialized in order to improve the value added. In the case of silage corn, there will be varieties of early maturing and late planting adaptability, with no more than 110 days until maturity, suitable for the cropping system, such as second cropping and double cropping, as well as high digestion rate and nutrition varieties with high feed value, and excessive water tolerance corn varieties that adapt well to paddy fields. Furthermore, it is expected that corn varieties that adapt well to Southeast Asia, Latin America, and Africa will continue to be developed and supplied.

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).

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).