Flower color is one of the key trait that determines the marketability of chrysanthemums. However, genetic research on chrysanthemum remains limited because of numerous environmental factors and the complexity of the chrysanthemum genome. To gain a deeper understanding of the genetic mechanisms underlying flower color in chrysanthemum, this study conducted genotyping analysis on 94 F₁ progenies derived from a cross between two wild chrysanthemum parents, ‘CWT2’ and ‘CWT8,’ which exhibit distinct flower colors. Genotyping-by-sequencing (GBS) was used for SNP identification, resulting in 79,002 single nucleotide polymorphisms (SNPs). After stringent filtering, 2,548 SNP markers were selected to construct a GBS-SNP linkage map, which was subsequently used to detect quantitative trait loci (QTLs) associated with flower color. Four QTL were identified, encompassing genes involved in carotenoid biosynthesis, carotenoid degradation, and the methylerythritol phosphate pathway. Among the 16 candidate genes analyzed for their potential role in flower color determination, three genes (VDE, CYP707A4, and CYP707A2) were ultimately selected for molecular marker development. The findings of this study provide a valuable foundation for understanding the genetic basis of carotenoid degradation in chrysanthemums. Future in-depth research is expected to facilitate the development of new chrysanthemum varieties for breeding programs through marker-assisted selection in breeding programs.

Chrysanthemum is the most popular ornamental plant, after roses and lilies. The cauliflower mosaic virus (CaMV) promoter, which remains the most widely used promoter in dicotyledons, is a very strong promoter with sufficient effects in most crops. However, weak expression has often been reported in Chrysanthemum. Therefore, we searched for constitutive promoters available in Chrysanthemum. Based on the transcriptome analysis data of Chrysanthemum, nine constitutively expressed genes were selected, and each promoter region (1.0–3.0 kb) was isolated by genome walking. Only two of the nine promoters expressed GUS in tobacco and chrysanthemums. The major motif of the CmERF promoter (U41, 2060 bp) was related to the regulation of ethylene (ERELEE4) or gibberellin (PYRIMIDINEBOXOSRAMY1 and WRKY71OS). Similarly, the motif of the CmGA2 ox promoter (U47, 1060 bp) also contained gibberellin signaling factors, such as PRIMIDINEBOXHVEPB1 and WRKY71OS. Both promoters showed strong systemic expression in tobacco using GUS staining. Although weaker than in tobacco, significant expression was confirmed in the flowers and stems in chrysanthemum. The results of the GUS activity assay using chrysanthemum transformants showed that the transgenic line (#12) containing the U47 promoter had higher expression in all tissues than that containing the 35S-CaMV promoter. The U41 promoter was found to have a higher expression than the 35S-CaMV promoter in the stem.

Chrysanthemum morifolium Ramat. is one of the major flowering crop plants worldwide. However, domestic chrysanthemum markets have recently faced a downturn. To stimulate related industries, breeding technologies and efficient protection systems using molecular markers must be established. However, high cost and intensive efforts are required to develop useful molecular markers for the chrysanthemum as it is a polyploid crop with highly complex genome organization. Thus, the aim of this research was to develop expressed sequence tag-based simple sequence repeat (EST-SSR) markers, which are applicable to the chrysanthemum breeding program and cultivar protection, based on next-generation sequencing technology. From the RNAseq data of the standard chrysanthemum cultivars ‘Jungwoon’ and ‘Seinoisei,’ we identified 31,121 SSR loci and further retrieved 1,846 polymorphic SSRs. To test the marker efficiency of the 1,846 SSRs, we first chose 50 of the SSRs and designed primers by using the flanking sequences. It is noted that the nine EST_SSR markers show a single band-like amplicon, which can be exploited in various genetic studies. We proceeded to polymorphism tests for those SSRs with 56 chrysanthemum cultivars, confirming that the average polymorphism index content (PIC) was 0.69±0.058. Among those, we found that six SSRs were sufficient to specify the genetic identities of 55 chrysanthemum cultivars, which may be useful for protections of the related cultivars, as well as breeding programs, in the future.

In ornamental crops, the color and shape of flowers are one of the important traits. Generally, flower colors are determined by accumulating pigments such as carotenoids, flavonoids, and betalains. Among them, flavonoids are responsible for broad ranges of colors. Chrysanthemums are one of the most popular ornamental crops in the world, and there have been many efforts to change their flower color. In chrysanthemum flowers, cyanidin-based anthocyanin confers pink or red color, whereas terpenoid-based carotenoids are mainly responsible for yellow and green colors. However, blue colored chrysanthemums do not occur in nature. To date, there have been attempts to obtain blue or violet-colored chrysanthemum flowers through the introduction of a novel gene for accumulating delphinidin-based anthocyanins, while other studies have reported changing endogenous metabolites through the reconstruction of flavonoid biosynthesis. Since various transcription factors are involved in the regulation of flavonoid biosynthesis, it is important to understand not only the structural genes, but also the transcription factors required for the modification of flavonoid-based flower color. Therefore, in this paper, we describe the flavonoid biosynthetic pathway and its regulation, and review previous studies on the change in flower color through modification of flavonoid biosynthesis. This effort could be an important milestone in successfully achieving the modification of chrysanthemum flower color by means of plant biotechnology.

Chrysanthemum (Dendranthema grandiflourm Kitamura) is a member of the Asteraceae and one of the important horticultural crops. The
objective
of this study was to construct a DNA profile database for identification of chrysanthemum varieties using simple sequence repeat (SSR) markers. In order to select SSR markers for the variety identification, we screened 587 SSR primers using 20 varieties. Among them, 27 SSR markers showed polymorphism. We finally selected 14 SSR markers showing peak clearance, high polymorphism and reproducibility in 20 varieties. In conclusion, DNA profile database for 147 chrysanthemum varieties were constructed by 14 SSR markers. A total of 79 SSR alleles were detected and three to ten alleles were detected with an average of 5.6 alleles per locus. The polymorphism information content value ranged 0.287 ~ 0.785 with an average of 0.598. Genetic relationship revealed that genetic distance of 147 varieties ranged from 0.44 to 1.00. The 143 varieties among 147 varieties were distinguished by 14 SSR markers but the 2 varieties developed by mutation breeding and natural variation were not distinguished from original varieties. These constructed SSR profile database will be useful for the selection of similar varieties for candidate variety and for solving problem relating to seed dispute and infringement of plant breeder’s right.

Plant regeneration protocols via adventitious shoot organogenesis from leaf segments of Chrysanthemum morifolium ‘Baekma’ were developed. The effects of plant growth regulators (BA, NAA, IBA, IAA and 2,4-D) and AgNO₃ were tested to figure out the optimal condition for shoot bud induction and shoot formation from leaf explants. On the combination treatment of plant growth regulators and AgNO₃, bud induction was obtained but shoot formation was not. Therefore, two-stage treatment of leaf explants was subsequently experimented for the respective improvement of adventitious bud induction and shoot formation. When leaf explants were cultured on bud induction medium (MS medium supplemented with 0.2 mg/L BA, 1.0 mg/L IAA and 1.0 mg/L 2,4-D) for 4 weeks in darkness and were transferred to shoot formation medium (MS medium supplemented with 1.0 mg/L BA, 1.5 mg/L IBA and 5.0 mg/L AgNO₃) for 4 weeks under the 16/8h photoperiod condition, shoot formation efficiency reached up to 50.0% and 1.6 shoots per explant were acquired. At 12 weeks after culture, the regenerated shoots were elongated and rooted on MS medium. The plantlets were acclimatized successfully and the regenerated plants exhibited normal phenotypes.