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).

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.

The 12 cultivars of the Jeju native Citrus are considered to have originated from China. However, the origin of the cultivar ‘Byungkyool’ (Citrus platymamma Hort. ex Tanaka) is not clearly known. We performed PCR analysis by using three primer sets designed from the internal transcribed spacer (ITS) region of nuclear ribosomal DNA (nrDNA) to analyze the phylogenetic relationship between the traditional citrus cultivars and the Byungkyool cultivar. Sequence length of the nrDNA ITS1 region of JNCPCRI (Jeju Native Citrus platymamma Citrus Research Institute) cultivar was 247 bp, 8the ITS2 region was 228 bp and the total ITS region (ITS1-5.8S-ITS2) was 638 bp. Analysis of the genetic relationship based on the sequence analysis at the ITS region of the JNCPCRI cultivar revealed that the ITS1 region of the cultivar was genetically the same as that of the Byungkyool (JQ990189) cultivar, and the ITS2 region was genetically similar to the Binkyool (JQ990180), Hongkyool (JQ990178), Dangyooja (JQ990179), and Pyunkyool (JQ990181) cultivars. Moreover, the total ITS region in the 5.8S rDNA region was genetically similar to the Hongkyool (JQ990178) cultivar. In addition, the total ITS region of the JNCPCRI cultivar was the most closely related to the Cheongkyool (JQ990183) cultivar and has been reported to originate from the Binkyool (JQ990180) and Pyunkyool (JQ990181) cultivars. Although the JNCPCRI cultivar was morphologically the same as the Byungkyool (JQ990189) cultivar, the ITS region showed genetic heterogeneity. Taken together, we conclude that the genetic variation in the ITS region of JNCPCRI cultivar suggests that it was propagated through fertilization with the surrounding citrus cultivars.