A new garden chrysanthemum (Dendranthema grandiflorum Ramat.) cultivar ‘Burning Ball’ was developed at the Flower Research Institute of Chungcheongnam-do Agricultural Research and Extension Services in 2011. ‘Burning Ball’ was bred in 2005 through a cross between the ‘05-72-04’ line with a red-purple flower color as the female parent, and the ‘04-26-22’ line with a red-purple flower color as the male parent. Adaptation trials were conducted for two years, from 2006 to 2007, under natural conditions. To identify morphological and genetic originality, we compared the external shape type with ‘Pretty Ball’ and conducted ploidy and RAPD (Random Amplified Polymorphic DNA) marker analyses. The results indicate that the ‘Burning Ball’ cultivar has unique characteristics compared to ‘Pretty Ball’. As a result, ‘Burning Ball’ will be favorably accepted as a novel bed chrysanthemum in the landscaping industry, contributing to farm income (Registration No. 4184)

As recent advances in gene editing technologies have enabled rapid and accurate modification of target genes, new varieties are being developed through the application of gene editing technologies in various crop species. In particular, the CRISPR/Cas9 system has become a tool of choice for gene editing because it is much more economical and efficient than previous tools such as ZFN and TALEN, and is being actively used to improve various breeding traits, including biotic and abiotic stress tolerance to overcome the limitations of conventional plant breeding technologies. In this review, we retrieved 210 papers describing the utilization of CRISPR/Cas9 in rice published between 2013 and 2021 and classified them according to the field of study and traits of interest. Further case studies were conducted on 21 and 12 research papers that reported the enhancement of biotic and abiotic stress tolerance, respectively. This demonstrated that CRISPR/Cas9-based gene editing can be highly effective in improving resistance to bacterial (bacterial leaf blight and bacterial leaf streak), fungal (blast, sheath blight), and viral (rice tungro spherical virus, rice black streak virus) diseases as well as various abiotic stresses, including drought, salinity, cold, and heat, in many cases, without diminishing important agronomic traits. As recent technological advances have begun to overcome the major limitations of CRISPR/Cas9 gene editing, such as low HDR efficiency and off-target effects, it is expected that more research on gene function and cultivar development will adopt CRISPR/Cas9 as a major gene editing tool in the future. To effectively apply such innovative technologies in crop improvement, much effort is required to establish more reasonable and detailed policies for regulating crops developed through new breeding technologies.

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.

Fast and accurate selection is essential for breeding to cope with rapid climate changes and a steeply increasing population. Consequently, technologies for high-throughput phenotyping (HTP) are emerging. These technologies, unlike conventional phenotyping methods, enable us to evaluate agronomic traits in a fast and massive manner. Thus, the HTP facility was built to acquire and analyze crop images using RGB sensors at the National Institute of Agricultural Sciences, Republic of Korea. By testing various conditions to acquire images, we determined the conditions for phenotyping using the RGB sensor as follows: exposure 30,000 ms, gamma 75, and gain 100 using LED lights in a blue background. Based on this condition, images from 96 individual plants of rice Dongjin cultivar were obtained every week to measure plant height and shoot area, which are directly associated with yield. The results obtained from the image analysis were compared with the manually collected results. The r² value between the projected plant height obtained from image analysis and the plant height obtained from manual measurement was 0.989. Furthermore, the r² value between the projected shoot area obtained from image analysis and the shoot area obtained from manual measurement was 0.981. These results show that image analysis is highly reliable and can be used for crop phenotyping. Therefore, we expect that the new method we developed will be used for breeding in the near future.

A dwarf mutant rice line was selected from an Ac/Ds insertion mutant population and named dwf1. The phenotype of F₁ and F₂ plants derived from a cross between dwf1 and Dongjin indicated that a single recessive gene is responsible for the mutant phenotype, and we named this gene dwf1. Resequencing of the dwf1 line and Dongjin (wild type) revealed 42,386 homozygous single nucleotide polymorphisms (SNPs) between dwf1 line and Dongjin. MutMap analysis was performed by sequencing a DNA pool prepared from 100 mutant type plants in the dwf1/Dongjin F₂ population, and it was found that the dwf1 gene was located in the 23 ~ 30 Mbp region on chromosome 4. In this region, we found a non-synonymous SNP in the Os04g0469800 gene, which was reported as D11 gene encoding a cytochrome P450 family protein involved in the biosynthesis of brassinosteroids (BRs). This SNP was regarded as the causative SNP for the dwf1 phenotype, and the dwf1 gene is a novel allele of D11. We performed mapping of the dwf1 gene with five SNP markers on chromosome 4 with 190 dwf1/Dongjin F₂ plants. The phenotype of F₂ plants was completely co-segregated with genotypes of the J10402 marker, which was developed based on the non-synonymous SNP in the D11 gene. These results will contribute to the study of the molecular biological functions of the D11 gene and BRs.

Perilla is an oilseed crop cultivated in Korea since ancient times. Due to the high α-linolenic acid content in perilla, perilla seed oil can easily become rancid. α-Linolenic acid is synthesized by two enzymes, endoplasmic reticulum-localized Δ15 desaturase (FAD3) and chloroplast-localized Δ15 desaturase (FAD7) in vivo. In order to lower the α-linolenic acid content of the seed oil without disturbing plant growth, we tried to suppress the expression of only the FAD3 gene using RNA interference, whilst maintaining the expression of the FAD7 gene. Seventeen transgenic plants with herbicide (Basta™) resistance were obtained by Agrobacterium-mediated transformation using hypocotyls of perilla plants. The transgenic plants were firstly confirmed by treatment with 0.3% (v/v) Basta™ herbicide, and the expression of FAD3 was measured by Northern blot analysis. The α-linolenic acid content was 10-20%, 30-40%, and 60% in two, seven, and three of the twelve T₁ transgenic perilla plants which had enough seeds to be analyzed for fatty acid composition, respectively. Analysis of the fatty acid composition of T₂ progeny seeds from T₁ plants with the lowest α-linolenic acid content showed that the homozygous lines had 6-10% α-linolenic acid content and the heterozygous lines had 20-26% α-linolenic acid content. It is expected that the reduction in α-linolenic acid content in perilla seed oil will prevent rancidity and can be utilized for the production of high-value functional ingredients such as high γ-linolenic acid.

Gayabyeo, a Tongil-type rice variety, has been known to be resistant to the brown planthopper (BPH) in Korea. For genetic analysis of BPH resistance of Gayabyeo, we developed an F2 and F3 population derived from a cross between Gayabyeo and Taebaegbyeo which is a Tongil-type BPH susceptible rice variety. Based on the previously detected 284,501 putative SNPs between Gayabyeo and Taebaegbyeo, 99 cleaved amplified polymorphic sequences (CAPS) markers were developed, and they have been used for genotyping 180 F2 plants. By comparison of resequencing data of Gayabyeo and the sequences of already reported BPH resistance genes (Bph3, BPH9, Bph14, BPH18, BPH26), it was revealed that Gayabyeo has Bph3 and BPH26 resistance genes. Two InDel markers, Bph3IND and BPH26IND, were developed, which can be used as selection markers in breeding program aiming at introducing BPH resistance genes of Gayabyeo into Korean high quality japonica rice varieties. In addition, BPH bioassay was performed with 180 F3 lines for BPH resistance QTL analysis. Two major QTLs were found on chromosome 4 and 12. The regions of these two QTLs included Bph3 and BPH26, which also supported that Gayabyeo has Bph3 and BPH26 resistance genes. These results would be useful in accelerating development of various BPH-resistant high quality japonica rice varieties in Korea.