‘Halla Green 12’ cultivar is characterized by Zoysia matrella×Zoysia japonica. It was selected as a warm season zoysiagrass with an extended greening period phenotype at low temperatures and a short plant height. Inflorescences of Z. matrella lines were collected near the boundary between wild Z. matrella lines and wild Z. japonica lines in Ora-dong, Jeju-do. Seeds were collected from the inflorescence and sown to obtain hybrid lines of Z. matrella and Z. japonica, ranging from the Z. japonica line to the Z. matrella line. Among the collected zoysiagrasses, a hybrid line of Z. matrella and Z. japonica, which showed a short height and characteristics of extended greening periods in greenhouses and test fields during winter, was finally selected and named ‘Halla Green 12’. Subsequently, it was registered in June 2022 (Registration No. 277). The test guideline (TG) of the Korea Forest Service was used to analyze the main external morphological characteristics of the ‘Halla Green 12’ cultivar, described as follows. ‘Halla Green 12’ cultivar has a short ‘Plant height’ (6.14±0.37 cm), ‘Leaf blade’ (4.15±0.36 cm), and ‘Leaf sheath’ (1.39±0.08 cm). The ‘Leaf angle’ is very wide at 61.5°. Since the ‘Leaf blade’ of ‘Halla Green 12’ has no ‘Trichomes,’ and the ‘Leaf blade width’ is as narrow as 1.69±0.06 mm, it is morphologically classified as a hybrid line of Z. matrella and Z. japonica, which is close to Z. matrella. In particular, during the winter period, ‘Halla Green 12’, which was grown in the test field, showed an extended greening period with green and reddish-purple leaf colors. The chlorophyll levels of the leaves of ‘Halla Green 12’ cultivar were 2580.2±175.6 nmol/mL/g, which were approximately 13.4-fold higher than those of the control variety ‘Yaji’ and 5.6-fold higher than those of the control Zm-6. ‘Halla Green 12’ showed the characteristics of extended greening period. Since the ‘Halla Green 12’ cultivar is characterized as Z. matrella×Z. japonica, which is close to Z. matrella with short ‘Plant growth’ and characteristics of extended greening periods, it is expected to be useful for reducing management costs, such as those attributed to mowing and industrializing lawn greening (Registration No. 277).

‘Halla Green 11’ is a Zoysia matrella cultivar showing short height and extended greening period lines at low temperatures of winter than general warm season zoysiagrasses. ‘Halla Green 11’ Z. matrella was collected from the seaside cliffs in Geogeum Island, Jeollanam-do. The turfgrass was transplanted to the genetic resources greenhouse and propagated in the test field. Among the zoysiagrasses cultivated in the greenhouse and test field, Z. matrella, which had a short height and showed extended greening period lines during the low temperatures of winter, was finally selected and named ‘Halla Green 11’ and was registered in June 2022. The main external morphological characteristics of the ‘Halla Green 11’ variety were analyzed using the test guideline (TG) of the Korea forest service, which is described as follows: Since the turfgrass has a ‘Leaf sheath’ of a short length, the mowing height can be lowered, rendering mowing easy. Furthermore, the ‘Plant height’ and the length of the ‘Leaf blade’ are short. The ‘Leaf blade width’ is narrow, and trichomes on the leaf surface are not present. Hence, ‘Halla Green 11’ is morphologically classified as Z. matrella. The leaf angle is very wide. The colors are green for ‘Leaf blade’, light green for ‘Leaf sheath’, and light purple for ‘Stolon’. Particularly, during the low-temperature period of winter, ‘Halla Green 11’ showed approximately 25.2, 10.6, and 8.1-fold high levels of leaf chlorophyll than the control cultivar ‘Yaji’, control Zm-6, and Zm-19, respectively. Owing to the short height of the plant and extended greening period phenotype, ‘Halla Green 11’ is expected to be highly preferred by consumers (Registration No. 274).

This superior zoysiagrass line was selected from the zoysiagrass genetic resources collected in the Republic of Korea. Inflorescences of Zoysia matrella lines were collected near the border between wild Zoysia japonica and wild Z. matrella on Jeju Island. Various Z. matrella×Z. japonica lines were obtained using the seeds from the collected inflorescences. In 2021, one of the lines that extended the greening period during the low temperatures of winter was registered under the name of ‘Halla Green 10’. The main morphological characteristics of this cultivar, which were analyzed using the test guidelines of the Korea Forest Service, are as follows: short length of plant (12.01±0.57 cm), short length of leaf blade (8.83±0.68 cm), and short length of leaf sheath (1.71±0.20 cm). The short length of leaf sheath makes it easy to manage the turf grass with low height. Due to the presence of trichomes on the leaf surface and medium-leaf type (leaf blade width: 3.0±0.16 mm), ‘Halla Green 10’ is morphologically classified as Z. matrella×Z. japonica. As the leaf angle is very wide at 77.7°, it has a high photosynthetic efficiency. The colors of the leaf sheath, leaf blade, and stolon are light green, green, and light purple, respectively. In particular, during the low temperature period of winter, the chlorophyll content of the leaves of ‘Halla Green 10’ shows about 7.5-fold from that of the control Z. japonia ‘Yaji’ and about 3.2-fold increase from that of the control Zm-6. Extending the greening period phenotype is expected to be commercially useful (Registration No. 246).

The ‘Halla Green 7’ cultivar is a hybrid of Zoysia matrella and Zoysia japonica. The inflorescences of Z. matrella lines were collected from Jeju Island near the border between Z. matrella and Z. japonica wild plants, respectively. After their harvest, the seeds were sown and various interspecific lines were obtained. In 2021, a line with greening period extending phenotype during the low temperatures of winter was registered under the cultivar name of ‘Halla Green 7’ (Registration No. 245). The main morphological characteristics of the ‘Halla Green 7’ variety are as follows: genetically short length of plant (12.2±0.58 cm), very wide angle of leaf (68.6°), short length of leaf blade (8.38±0.37 cm), medium-leaf (3.29±0.09 mm), and very low leaf sheath (2.18±0.19 cm). The short length of leaf sheath makes it easy to manage the turf grass with low height. A very wide leaf angle has a high photosynthetic efficiency. The ‘Halla Green 7’ cultivar is morphologically classified as Z. matrella×Z. japonica hybrid line by medium-width of leaf blade and the presence of trichomes on the leaf surface. The colors of the leaf blade, leaf sheath, and stolon are green, light green, and light purple, respectively. During the low temperature period of winter, chlorophyll content of the leaves of ‘Halla Green 7’ shows a 10.1-fold from that of the control Z. japonia ‘Yaji’ and about 4.2-fold from that of the control Z. matrella Zm-6. This greening period extending phenotype is expected to contribute to the industrialization of zoysiagrass (Registration No. 245).

This study was carried out to develop new zoysiagrass (Zoysia japonica Steud.) cultivar ‘Halla Green 2’ (Grant number: No. 118). To develop a zoysiagrass cultivar with dwarfism by using the mutation breeding method, the wild type control "Gosan" plants were irradiated using a 30 Gy gamma ray source in 2010. Dwarf mutants were selected from the mutated grasses in successive generations. Dwarf mutant lines were identified and a new zoysiagrass variety Halla Green 2 was developed. The plant height of Halla Green 2 was 3.4 and 1.8 times lower than that of Gosan and Zenith, respectively. This cultivar has dwarf characteristics such as shorter sheath, shorter leaf blade, shorter flag leaf, and shorter third internode of stolon compared to those of Gosan and Zenith. Additionally, the sheaths and leaf blades color of Gosan, Zenith and Halla Green 2 were all light green, whereas their stolons were purple, yellow-green and yellow green, respectively. Trichomes(hairs) were visible on both adaxial and abaxial surfaces of the Gosan leaves, whereas only on the adaxial side of the Zenith and Halla Green 2 leaves. The Halla Green 2 grass showed distinguishable morphological traits compared to those of wild type Gosan and Zenith.

To develop a dwarf turfgrass (Zoysia japonica) cultivar with artificial mutation-induced breeding method, the wild type control "Gosan" plants were exposed to a 30 Gy gamma ray source in 2010. The mutant lines showing short height were selected from successive generations. One of the resulting dwarf lines obtained was registered under the cultivar name of “Halla Green 1” (2016). The dwarf phenotype of the Halla Green 1 includes a reduction of the height by 4.5-fold, an increase in leaf and third internode lengths by about 6- and 2.3-fold, respectively, compared to the Gosan, and approximately 2.4-, 3.8-, and 1.5-fold relative to the Zenith, respectively. In addition, the Halla Green 1 had a sheath of darker green coloring compared to the light green Gosan and Zenith. The leaf blades of Gosan, Zenith and Halla Green 1 were all light green, whereas their stolons were purple, yellow-green and light purple, respectively. Trichomes presented on both adaxial and abaxial surfaces of the Gosan’s leaves, and only on the adaxial side of the Zenith’s leaves, but none on the Halla Green 1 leaves. The Halla Green 1 exhibited sufficiently distinct morphological traits when compared with the wild type Gosan and Zenith that the dwarf phenotype enhances its commercial viability.