The newly developed citrus cultivar, ‘Miraehyang’, was bred at the Citrus Research Center of the National Institute of Horticultural and Herbal Science (Jeju, Korea) by crossing ‘Ehime Kashi No.28’ (maternal parent) and ‘Hayaka Ponkan’ (paternal parent). The first fruiting of ‘Miraehyang’ occurred in 2016, and field evaluations were conducted until 2021. After final selection in 2021, the cultivar was officially registered for plant variety protection in 2024. The tree exhibits strong vigor, an open growth habit, and high fruit-bearing capacity. When grown in a plastic greenhouse, ‘Miraehyang’ showed minimal occurrence of puffing and fruit-cracking. New shoots emerged in late March, and flowering began in late April, with full bloom occurring in mid-May. The average fruit weight was between 150-200 g, and the fruit shape slightly flattened with a small apex. Coloring started in mid-October and completed by mid-December, resulting in a deep orange hue. The fruit is rich in juice with thin membranes, providing a tender texture. Under unheated greenhouse conditions, the fruit matured in mid-to-late December and had a soluble solids content of 12-13°Bx and acidity of approximately 1.0%. Peel thickness averaged at 3.3 mm, similar to that of ‘Ehime Kashi No.28’, but with improved ease of peeling. This cultivar is male-sterile, producing seedless fruit when grown alone. Similar to its maternal parent, ‘Ehime Kashi No.28’, ‘Miraehyang’ is susceptible to citrus canker but resistant to scab. ‘Miraehyang’ is expected to gain high consumer preference due to its ease of cultivation, superior peelability, and outstanding fruit quality and appearance (Variety registration number: 10180).

‘Inchangkyool’ varieties, which are believed to have been cultivated in Jeju for a long time, have leaves and flowers with a lemon-like fragrance. They have been suggested to be given the same scientific name as Citrus ichangensis, which is known to originate from China’s Southwest and Midwest regions. However, the genetic characterization of ‘Inchangkyool’ has not been reported, and literature is not readily available. Hence, in this study, 30 citrus chloroplast (cp)DNA (trnL-trnF) regions and nuclear ribosomal DNA internal transcribed spacer (ITS) regions were tested to identify the genetic relationship between ‘Inchangkyool’ and C. ichangensis and the origin of ‘Inchangkyool’ cultivars. Our results indicated that the total nucleotide sequence length of the trnL-trnF intergenic spacer (IGS) region and the G + C content was 373 bp and 36.73%, respectively, in the cpDNA of C. ichangensis and ‘Inchangkyool’, whereas the ITS1 regions were 247 and 248 bp and the ITS2 regions were 228 and 226 bp, respectively. Furthermore, the sequence lengths of the total ITS (ITS1 + 5.8S rDNA + ITS2) regions were 638 and 637 bp, respectively, whereas the G+C content was 70.16%, 71.26%, 69.03%, 70.61%, 64.6%, and 65.49%, respectively - showing differences in the nuclear ribosomal DNA region. However, the nucleotide sequence length of the 5.8S rDNA region was 163 bp and the G + C content was 54.6%, which were the same for both varieties. In addition, sequence divergence and phylogenetic analysis of the trnL-trnF and ITS regions in chloroplast DNA showed that the sequence divergence of the trnL-trnF region on the chloroplast was 0–0.008. This result indicates that ‘Inchangkyool’ is most closely related to Jeju eight native citrus cultivars including ‘Dongjeongkyool’. It is also closely related to C. ichangensis cultivars and six common citrus cultivars. In other words, the ‘Inchangkyool’ cultivar was inherited from the same maternal line as the Chinese C. ichangensis. The divergence values of the nuclear ribosomal DNA region between ‘Inchangkyool’ and ‘Dongjeongkyool’ and C. ichangensis were 0.008 and 0.026, respectively. These results indicated that ‘Inchangkyool’ was most closely related to ‘Dongjeongkyool’, and was farther from the C. ichangensis cultivar. In addition, phylogenetic relationships found ‘Inchangkyool’ to belong to the same group as the ‘Dongjeongkyool’ cultivar of jeju native citrus cultivars and a different group from C. ichangensis. From the above results, it is suggested that ‘Inchangkyool’ cultivar has been classified from the same maternal cultivar as the C. ichangensis in China, but has been obtained through long-term crossing with the same species as ‘Dongjeongkyool’. Moreover, based on the above results, it is believed that a distinct cultivar name for ‘Inchangkyool’ can be presented.

A new citrus cultivar ‘Tamdosamho’ is a hybrid obtained from a cross of ‘Kiyomi’ (Citrus unshiu×Citrus sinensis, the seed parent) and ‘Sunburst’ (Citrus reticulate, the pollen parent) at the Citrus Research Institute of the National Institute of Horticultural and Herbal Science in 2004. ‘Tamdosamho’ had the first fruit set in 2010 and field evaluation has been conducted until 2012. The tree of ‘Tamdosamho’ was vigorous and had a lot of fruit bearing. The average fruit weight was 230g and its shape was flatten-oblate with a little neck. The fruit peel color was dark orange, and peel coloration began in mid-October and fully developed in early December. The fruit matured in mid-February from cultivation under plastic film house. Total soluble solid and acidity of which was 14.0 °Brix and about 1 % respectively. The thickness of the rind was about 2.5 mm on average and was thinner than that of satsuma mandarin (Citrus unshiu), so removing the peel was easy. This cultivar had characteristic of self-incompatibility and parthenocarpy and didn’t bear seeds from monoculture but if it be fertilized by the pollen of other cultivars could be seedy. In the case of cultivation in the open field, the fruits could be damaged by cold temperature and then ‘Tamdosamho’ is recommended for cultivation under plastic film house. (Variety registration number: 6158)

A new mandarin hybrid cultivar ‘Shinyegam’ was developed from a cross between ‘Kiyomi’ (Citrus unshiu × C. sinensis) and ‘Wilking’ (Citrus reticulata) at the Citrus Research Institute of the National Institute of Horticultural and Herbal Science in 2012. The ‘Jegam na No. 33’, a first selection seedling from the fruits obtained in 2008 was finally named ‘Shinyegam’ after field evaluation trials at five locations in Jeju island, Korea from 2010 to 2012. The tree vigor was intermediate and the tree was spreading in nature, similar to that of the ‘Kiyomi’ cultivar. The fruits produced were compressed to oblate and globose in shape, were a deep orange in color, and moderately weighed at 130 g. ‘Shinyegam’ produces fruit that mature in late December, and has few seeds, which are mono-embryonic. The average seed number of a fruit varied depending on the pollinator citrus tree. Cultivation of ‘Shinyegam’ along with the other cultivars possessing high pollen fertility resulted in seed numbers that was more than 20, while in the absence of a pollinator species the seed number was around 5. The fruit contained soluble solids at 11 to 12 ° Bx and the acidity was approximately 1% at maturity. The rind thickness of approximately 2.5 mm ensures easy peeling. The flesh is very tender and juicy, with a pleasant, aromatic flavor similar to that of ‘Wilking’ but is comparatively weak. ‘Shinyegam’ is moderately resistant to the citrus scab disease and melanose, but susceptible to citrus canker. Owing to the high quality of fruit, good aroma, and cold hardness characteristics, this cultivar is expected to satisfy consumer acceptability in terms of the diversity of the cultivar in open-field cultivation.