‘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).

Here, we report on the development of a high-quality, bicolor waxy corn, ‘Mihyeonchal’, containing anthocyanin. ‘Mihyeonchal’ was produced by crossing the two inbred lines, HW18 as the seed parent and HW19 as the pollen parent. The hybrid was made in 2016 and has been evaluated for three years in Hongcheon, Yeoncheon, Cheongju, Daegu, Jinju, and Suwon in Korea since 2017. The days to silking of ‘Mihyeonchal’ was 72 days, which was three days earlier than that of the standard variety, ‘Ilmichal’. The number and weight of fresh ears of ‘Mihyeonchal’ were 112% and 96%, respectively, compared to those of ‘Ilmichal’, and the anthocyanin content was 76.8 mg/kg, which was higher than that of ‘Ilmichal’. The lodging index was 1.9, which was weaker than that of ‘Ilmichal’, but its resistance to insects and diseases was stronger than that of ‘Ilmichal’, confirming the cultivation stability of ‘Mihyeonchal’. As a result of regional yield trials that had been conducted for three years, we confirmed that ‘Mihyeonchal’ could be cultivated in all regions in Korea and was an excellence variety. The plant variety protection right of ‘Mihyeonchal’ was registered in April 2024, and its grant number is 10127.

Doubled haploid (DH) technology is widely used in maize breeding because of its ability to produce 100% homozygous inbred lines within a short period of time. This efficiency has made DH technology an attractive tool for maize breeders, allowing its incorporation into breeding programs. This technology also facilitates advanced breeding techniques such as genome editing and the conversion of elite inbred lines into their cytoplasmic male sterility counterparts. The successful integration of DH technology into various maize breeding programs worldwide has spurred extensive research on the genetic basis and mechanisms underlying haploid induction, leading to the identification of key quantitative trait loci (QTL) aimed at improving efficiency and reducing costs. Additionally, new phenotypic markers are being explored for use along with the R1-nj marker to enhance the accuracy of haploid seed and plant identification. Efforts are underway to identify alternatives to colchicine, a toxic and carcinogenic compound commonly used for chromosome doubling. Nondestructive methods, such as nuclear magnetic resonance, Fourier transform Raman spectroscopy, and flow cytometry, are being developed to enable fast and accurate haploid identification and automate the process for large-scale breeding programs. As these advancements improve DH technology, the maize hybrid breeding paradigm is undergoing a substantial transformation. However, several challenges remain unaddressed.

‘KM3’ is an F1 hybrid maize developed by the maize breeding team at the National Institute of Crop Science (NICS), Rural Development Administration (RDA), for the Southeast Asian seed market. This hybrid was obtained by crossbreeding two inbred lines—14K26 and 15VL027. The hybrid was evaluated in a crop-year yield trial in Cambodia, followed by country adaptability trials in Cambodia and Indonesia in 2016 and 2017, respectively. The flint-like seed type of ‘KM3’ makes it suitable for both food and feed, demonstrating its adaptability to Southeast Asia. ‘KM3’ exhibited early maturity, high grain yield as an F1 hybrid, and resistance to downy mildew. The silking date of ‘KM3’ was two days earlier than that of the leading cultivar ‘CP888’ in Cambodia, with a grain yield of 913 kg/10a, outperforming ‘CP888’ by 26% (Registration No. 9319).

‘KM5,’ a high grain yielding maize hybrid, was developed for the Southeast Asian seed market in 2018 by the maize breeding team of the National Institute of Crop Science (NICS), Rural Development Administration (RDA). ‘KM5’ was bred by crossing two inbred lines—14K23 and CL59. After a 1-crop year yield trial in Dong Trieu and Vietnam, country adaptability trials were performed in 2017 and 2018 in three different countries—Vietnam, Cambodia, and Indonesia. The seed type is flint-like and suitable for both food and feed. ‘KM5’ adapted well to northern Vietnam, northwestern Cambodia, and Central Java in Indonesia. It is an early maturing, high grain yield F1 hybrid that is also resistant to downy mildew. The silking date of ‘KM5’ in Vietnam is 74 days, which is the same as that of LCH9—a leading cultivar in Vietnam. ‘KM5’ produced a grain yield of 695, 764, and 678 kg/10a in Vietnam, Cambodia, and Indonesia, respectively, thus demonstrating a higher yield than the leading cultivar in each country. ‘KM5’ produced 2%, 27%, and 8% more grain than the respective control varieties in Vietnam, Cambodia, and Indonesia, respectively (Registration No. 8947).

We report the development of a high quality red waxy corn ‘Mihongchal’, containing anthocyanin. Mihongchal was produced by crossing two inbred lines, ‘HW9’ as seed parent and ‘HCW5’ as pollen parent. The hybrid was created in 2016 and evaluated in Hongcheon, Pyungchang, and Yeongwol for 3 years. Mihongchal days to silking was 72 days and the other agronomic characteristics were similar to ‘Mibaek 2ho’. Mihongchal yield was slightly lower than ‘Mibaek 2ho’. Fresh ears number and weight were 93 and 91% compared to ‘Mibaek 2ho’, respectively but anthocyanin content was 1,160 mg/kg, which is higher than ‘Mibake 2ho’. Resistance to insects, diseases, and lodging was similar to ‘Mibaek 2ho’. Due to the analysis, it was recognized as functional waxy corn with high quality characteristics and anthocyanin content. Since regional yield tests was performed in only Gangwon State, it is recommended only in that region for cultivation. Mihongchal is a resource with excellent taste and functionality that can increase the value of waxy corn. The chosen variety was termed ‘Mihongchal’, its plant variety protection right was registered in February 2023 (Registration No. 9354).

Many studies concerning breeding maize varieties are in progress in Korea and other countries. Double haploid technology is widely used for the development of commercial maize varieties worldwide, and has also been utilized in Korea since its introduction by the Maize Research Institute, Gangwondo. We performed a study to improve the efficiency of selecting haploid maize seeds using fluorescence imaging. It was verified that anthocyanin produced by the expression of R1-nj gene can be detected by fluorescence imaging, and we developed a high-throughput method for discriminating between haploid and diploid seeds. Compared with discriminating with naked eye, this method reduced the time for discriminating haploid and diploid maize by 91.7% and increased selection accuracy by 16.8% for haploid and 2.2% for diploid maize. This method enabled the acquisition of more haploid seeds and improved the efficiency of breeding research by shortening the time involved.

A new anthocyanin-rich hybrid variety, ‘Saekso 1’, is developed which is characterized by yellow grains, and purple husks and cobs. This variety was produced by crossing two inbred lines, ‘HA1’ (as the seed parent) and ‘HA2’ (as the pollen parent). It was made in 2008/2009 and evaluated in Hongcheon for two years. After evaluation, the selected variety was named ‘Saekso 1’ and was approved for a variety registration in 2014. The anthocyanin content of ‘Saekso 1’ in husk was 10.39±0.09 g/100 g, which was much higher than that of Kangilok (0 mg/100 g). Since regional tests were conducted only in Gangwon province, this variety is recommended only in that region for commercial cultivation. ‘Saekso 1’ is a health food resource for bioactive materials (Registration No. 4967).

‘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).

In this study, 14 agricultural and phenotypic traits were used to analyze morphological variations among 10 near-isogenic lines (NILs) of colored waxy maize and 2 parental lines (HW3 and HW9) of the hybrid cultivar “Mibaek 2.” The results of principal component analysis indicated that on the first principal component axis, seed coat color, R value, V value, days of tasseling, L* value, and days of silking greatly contributed to the positive direction, whereas anthesis–silking interval and leaf width greatly contributed to the negative direction. On the second principal component axis, kernel row number and tassel color contributed to the positive direction, whereas setted ear length, ear length, and 100-kernel weight contributed to the negative direction. Thus, the morphological characteristics that greatly contributed to the first and second principal components might be useful for discrimination among the 10 NILs and 2 parental lines of “Mibaek 2.” Of the 10 NILs analyzed, 16CLP26 and 16CLP16 were considered useful breeding material for the development of colored waxy maize varieties with relatively high amounts of yield and anthocyanin. Collectively, these results are expected to provide useful information for the development and selection of lines for breeding colored waxy corn varieties at the Maize Research Institute, Gangwon-do Agricultural Research and Extension Services.

‘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).

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.

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)

Salt stress is a significant factor limiting growth and productivity in crops. However, little is known about the response and resistance mechanism to salt stress in maize. The
objective
of this research was to develop an enhanced salt-tolerant silage maize by mutagenesis with gamma radiation. To generate gamma radiation-induced salt-tolerant silage maize, we irradiated a KS140 inbred line with 100 Gy gamma rays. Salt tolerance was determined by evaluating plant growth, morphological changes, and gene expression under NaCl stress. We screened 10 salt-tolerant maize inbred lines from 2,248 M₂ mutant populations and selected a line showing better growth under salt stress conditions. The selected 140RS516 mutant exhibited improved seed germination and plant growth when compared with the wild-type under salt stress conditions. Enhanced salt tolerance of the 140RS516 mutant was attributed to higher stomatal conductance and proline content. Using whole-genome re-sequencing analysis, a total of 328 single nucleotide polymorphisms and insertions or deletions were identified in the 140RS516 mutant. We found that the expression of the genes involved in salt stress tolerance, ABP9, CIPK21, and CIPK31, was increased by salt stress in the 140RS516 mutant. Our results suggest that the 140RS516 mutant induced by gamma rays could be a good material for developing cultivars with salt tolerance in maize.

Maize is the most important grain crop in the world. Genetic engineering technology has been used to enhance its various agronomical traits. The transformation of maize is a crucial step in the application of gene technologies to improve maize. The choice of genotype and explant material influences the transformation efficiency and the production of stable transgenic plants. Immature embryos of Hi IIA were infected with Agrobacterium tumefaciens LBA4404 including superbinary vectors (bar and GUS or GFP genes). The transformation efficiency was based on transgenic calli induction from immature embryos on the selection medium with 3 mg/L bialaphos. The transformation efficiency varied from 1.01 to 2.74%. The integration and expression of bar, GUS, and GFP genes were confirmed in T₀ and T₁ generations of transgenic plants using genomic PCR and the bar strip test. In addition, herbicide resistance in T₁ transgenic plants was observed when leaves and whole plants were treated with Basta. These results suggest that the successful Agrobacterium-mediated transformation of Hi IIA will improve further opportunities for functional genomic and genome editing studies in maize.

‘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).

Drought stress during the seedling stage has a disastrous effect on the growth of maize. The purpose of this study was to assess the developed expression markers that are related to drought stress in maize. For the selection of expressed genes by drought stress, co-expression analysis was carried out using published microarray data of drought stress in maize (Zea mays L.) seedlings. Six consensus modules were based on 4,770 stress responsive genes differentially expressed in drought stress, and the royal blue module was chosen. Thirty genes were selected according to different expression patterns between susceptible and tolerant types. Drought stress treatments were performed on both Ki3 and Ki11. Ki3 and Ki11 are widely known drought-susceptible and -tolerant types, respectively. At first, the 30 selected genes were compared to Ki3 and Ki11 using qRT-PCR. The gene expression values of eight genes (BU050895, BF728598, CK827168, CO524848, AF457983, CF037152, AJ606944, and BG836522) were significantly tolerant types rather than susceptible types in the roots. After applying the eight above-mentioned genes to nine cultivars, a different pattern was detected between susceptible and tolerant types. The results of the present study will show the possibility of developing novel expression markers and the application for various maize varieties.

‘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)

We report the development of new anthocyanin-rich grain corn hybrid variety ‘Saekso 2’. The seed parent, HA3 and the pollen parent, HA4 was developed from breeding materials collected from China in 2008 and from Canada in 2000, respectively. The hybrid was made in the winter of 2010/2011 and evaluated in Hongcheon for 3 years. After evaluation, the selected variety was named ‘Saekso 2’ and was approved for a variety registration in 2017. Anthocyanin content of Saekso 2 in grain was 685 mg/100g and was much higher than that of Saeko 1(0mg/100g). Since regional tests was conducted in only Gangwon province, it is recommended only in that region for commercial cultivation. For the highest content of anthocyanin, it is best to harvest grains at around 45 days after silking. Saekso 2 is the first hybrid bred specifically for processing for high anthocyanin production.

We collected 32 maize inbred lines from eastern cereal and oilseed research center in Canada to develop new maize varieties. We also evaluated genetic diversity, genetic relationships, and population structure using 35 SSR markers. A total of 269 alleles were revealed in 35 loci with an average of 7.69 and a range between 3 and 15 alleles per locus. The genetic diversity values varied from 0.176 to 0.889 with an average of 0.691. The polymorphic information content varied from 0.171 to 0.879 with an average of 0.659. Population structure analysis indicated that 32 Canadian maize inbred lines comprised four major groups and one admixed group based on a membership probability threshold of 0.80. The four major groups contained 13, 2, 5 and 2 maize inbred lines, respectively. From genetic relationships analysis, the all inbred lines were divided into three main groups at 26% genetic similarity. Group I included 22 inbred lines, and Group II included 9 inbred lines. Group III consist of only one inbred line. The results in this study would be useful for the improvement and development of new cultivars, planning crosses for hybrids or development of inbred line in maize breeding program

‘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.

In order to develop a core set and new corn variety in Korea, we evaluated the morphological characteristics of 194 maize accessions by examining eight quantitative characteristics. On the evaluation of quantitative traits for 194 maize accessions, they showed the morphological variations in tassel length (35.1±5.0 cm), plant height (226.1±33.7 cm), ear height (86.3±22.6 cm), stem diameter (2.3±0.6 cm), leaf width (9.3±1.1 cm), ear length (14.5±2.4 cm), ear row number (14.1±1.9 row), and 100 kernel weight (24.9±4.4 g). The results of principal component analysis (PCA) indicated that the tassel length, plant height, and ear height greatly contributed to positive direction on the first principal component axis. One-hundred kernel weight contributed to negative direction on the second principal component axis. Thus these morphological characteristics, which contributed greatly in the first and second principal components, might be useful for discrimination among 194 maize accessions. In our study, seven accessions, such as IT026357, IT026441, IT027321, IT033271, IT033591, IT033597 and IT124273, particularly were measured high on yield-related traits. Consequently, the 194 maize accessions used in this study could be used as promising materials for maize breeding programs such as development of new hybrid in Korea.

Anther culture is useful and significant tool for producing haploid or doubled haploid (DH) plants in crop breeding system. Androgenesis is the way of inducing haploid and DH plants from anther (immature pollen) or microspore culture. In vitro androgenesis is efficient technique for introducing complete homozygous lines in one generation, thus less time and expense could be necessary than conventional plant breeding. In maize, anther culture is important system for shortening the breeding cycle and enhancing selection efficiency. Anther culture technique is also applicable to various researches such as molecular genetics, genetic engineering, genomics, and plant biotechnology. We review the past and present studies on anther culture and provide useful information for future researches on androgenesis in maize. The combination of androgenesis with other techniques such as molecular breeding and biotechnology is producing a variety of variety of maize species. In addition, we suggest strategy to develop androgenesis technique adapted to Korean research environment.

Grain yield, agronomic traits, and correlation between genetic distance of 36 F₁ hybrids produced by half-diallel crosses using nine maize inbred lines were analyzed. In the analyses of F₁ hybrids and their mid-parent heterosis (MPH) for agronomic traits, grain yield showed highest MPH value of 156%. One-hundred kernel weight showed the lowest value of 7%. In addition, when genetic distance based on agronomic traits was estimated, parental inbred lines did not agree with their own pedigree. Therefore it had the limitation to estimate genetic distance using agronomic traits. In this study, 92 SSR markers were used to calculate genetic distance at DNA level. However we did not confirm their own pedigree of nine parental inbred lines. There was no correlation between grain yield and SSR markers. Therefore molecular marker selection was conducted in relation with grain yield by the step-by-step method using 92 SSR markers. The selected nine SSR markers showed a significant positive correlation (r²=0.703**) between grain yield and SSR markers. The correlations between the selected SSR markers and agronomic traits of ear length, ear width, plant height, and ear height were particularly showed positively correlated. The nine SSR markers selected in this study would help predicting heterosis and planning crosses for hybrids in maize breeding programs.

‘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.