Ⅰ. INTRODUCTION
Italian ryegrass (Lolium multiflorum Lam.) is one of the most widely cultivated winter forage crops in Korea owing to its high productivity, excellent palatability, and adaptability to paddy field cultivation (Choi et al., 2018;Song et al., 2023;Woo et al., 2025). This crop occupies a substantial proportion of the winter forage production area and serves as an important feed resource for domestic livestock production (Ku et al., 2023). As demand for high-quality forage continues to increase, the development of improved cultivars has become a key strategy for enhancing forage productivity and reducing dependence on imported feed resources (Kim et al., 2020).
For many years, breeding programs in Korea have focused primarily on developing early-maturing cultivars suitable for paddy-based double-cropping systems (Oh et al., 2021). Early heading allows forage harvest before rice transplantation, making these cultivars highly compatible with traditional farming practices. Consequently, early-maturing cultivars play a major role in expanding forage production and improving forage availability in paddy fields (Choi et al., 2011;Song et al., 2023).
Recently, however, agricultural production environments have undergone considerable changes. Rising temperatures and increasingly variable weather conditions influence crop growth and development, and changes in cropping systems have reduced the constraints associated with rice-based double cropping in some regions (IPCC, 2023). These trends have increased interest in cultivars that can provide greater forage yield and improved feed quality rather than early maturity. Among the available maturity groups, medium-maturing cultivars generally have advantages in terms of their biomass production and forage quality. However, the availability of medium-maturing cultivars with high productivity and stable adaptations remains limited. Therefore, breeding efforts are required to develop new cultivars capable of maintaining stable performance across diverse environments while producing greater dry matter yield (DMY).
Improving forage productivity is particularly important in Korea, where the land available for forage cultivation is limited and the livestock industry continues to rely on imported forage resources. The development of high-yielding domestic cultivars can strengthen forage self-sufficiency, improve farm profitability, and enhance competitiveness of the domestic forage industry.
Therefore, this study was conducted to develop a new medium-maturing Italian ryegrass cultivar with high dry matter yield, stable agronomic characteristics, and superior adaptation to Korean growing conditions.
Ⅱ. MATERIALS AND METHODS
This study was conducted at the Forage Production Systems Division, National Institute of Animal Science (NIAS), Republic of Korea, from 2011 to 2024 to develop a new medium-maturing cultivar of Italian ryegrass.
1. Crossing combinations
Between 2011 and 2013, five vegetative Italian ryegrass lines (13LmEs16, 13LmCb04, 13LmCb11, 13LmCb18, and 13LmCb19) were selected and used as parents for synthetic population development.
2. Establishment of synthetic populations
In 2014, a synthetic plot was established using a triangular polycross design to produce seeds using multi-parental crossing combinations. To prevent contamination by foreign pollen, rye was planted around the polycross blocks.
3. Performance evaluation and regional adaptation trials
Forage productivity and regional adaptability of IRG were evaluated through multi-location field trials. The study began in Cheonan in 2021, and evaluations were continued from 2022 to 2024 at four sites located in Cheonan, Pyeongchang, Jeongeup, and Jinju under a collaborative breeding project supported by the Rural Development Administration (RDA).
The widely cultivated domestic IRG cultivar ‘Kowinearly’ commonly grown in Korea, was used as the control cultivar. Sowing was performed in late September at all locations. The experimental plots were arranged in a randomized complete block design with three replicates. Seeds were drilled into 20-cm rows at a seeding rate of 30 kg/ha.
Fertilizers were applied at a total rate of 200–150–150 kg/ha (N-P2O5-K2O). The nitrogen fertilizer was split as follows: 20% before sowing, 50% during spring regrowth, and 30% after the first harvest to promote regrowth. Phosphorus and potassium fertilizers were equally divided between basal and early spring applications.
Agronomic traits, including winter hardiness, heading date, lodging resistance, disease resistance, plant height, leafiness, and regrowth ability were investigated during the growing period. Dry matter productivity was determined by harvesting the entire 6 m2 (2 × 3) plot area and converting the measured yield into hectares.
Morphological characteristics were investigated at the Cheonan site. Winter hardiness was visually scored on a scale of 1–9, where 1 represented strong tolerance and 9 indicated weak tolerance, based on winter survival and ground cover observed in early spring across all test locations.
For dry matter (DM) determination, forage samples (300–400 g) collected at harvest were dried in a forced-air oven at 65°C for at least 72 h. Dry matter percentage and yield were calculated using the following equations:
Crude protein (CP) concentration was determined according to AOAC procedures (AOAC, 2005). Neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents were analyzed following the procedures described by Goering and Van Soest (1970). Total digestible nutrients (TDN) were analyzed and calculated using the method described by Menke and Huss (1980).
Statistical analyses were conducted using SAS software (SAS Institute, 2004). Analysis of variance (ANOVA) was performed and mean comparisons among cultivars were evaluated using Duncan’s multiple range test.
Weather conditions varied considerably across years, particularly during winter (Table 1). January minimum temperatures ranged from -4.3 to 0.6°C in 2022, -4.0 to 0.4°C in 2023, and -4.1 to 1.7°C in 2024 across the four experimental locations. January precipitation was relatively low in 2022 (0.0–3.7 mm) but increased markedly in 2023 (22.1–67.3 mm) and 2024 (31.5–67.9 mm). These differences indicated that the experimental materials were exposed to contrasting winter environments during the evaluation period.
Ⅲ. RESULTS AND DISCUSSION
1. Morphological characteristics
The agronomic characteristics of the new Italian ryegrass (IRG) cultivar ‘Aura’ are presented in Table 2. Compared with the control cultivar ‘Kowinearly’, ‘Aura’ exhibited a tetraploid characteristic and showed a semi-erect growth habit before winter and an erect growth habit during spring growth. Leaf color was similar between the two cultivars and was classified as green. At the heading stage, ‘Aura’ showed superior morphological traits associated with biomass production. Plant height reached 105 cm, which was approximately 11 cm taller than ‘Kowinearly’, In addition, spike length and number of spikelets were greater in ‘Aura’, Plant height and other biomass-related traits are considered important selection criteria in forage breeding because of their association with forage yield (Casler and Van Santen, 2010). Leaf blade width was also wider in ‘Aura’ (8 mm) than in ‘Kowinearly’ (7 mm), suggesting enhanced leaf development and leafiness. The heading date of ‘Aura’ was May 11, approximately 10 days later than that of ‘Kowinearly.’ Although medium-maturing cultivars have generally been regarded as less favorable for paddy-upland double-cropping systems because of their later maturity, recent climatic changes characterized by warmer spring temperatures and longer growing seasons may enhance their suitability for Korean forage production systems. Therefore, medium-maturing cultivars such as ‘Aura’ could provide advantages through extended vegetative growth and increased forage accumulation under changing climatic conditions.
2. Winter survival
The winter survival performance of ‘Aura’ was evaluated from 2022 to 2024 in Cheonan, Pyeongchang, Jeongeup, and Jinju (Table 3). Overall, both cultivars showed excellent winter survival, with scores close to 1.0, indicating strong overwintering ability. No winter injuries were observed at Cheonan or Pyeongchang during the experimental period. In Jeongeup and Jinju, slight variation occurred in 2024 for ‘Kowinearly’ whereas ‘Aura’ maintained stable winter survival with a score of 1.0. The average winter survival score of ‘Aura’ across all regions was slightly better than that of the control cultivar. These results indicate that ‘Aura’ possesses stable cold tolerance under diverse environmental conditions. Winter hardiness is considered one of the most important traits determining the adaptation and persistence of forage grasses in low-temperature environments (Casler and Van Santen, 2010). Therefore, the stable overwintering ability observed in ‘Aura’ suggests that the cultivar can be reliably cultivated in both central and southern regions of Korea.
3. Dry matter yield
The dry matter yield of ‘Aura’ was consistently higher than that of the control cultivar across most test locations and years (Fig. 1). The average dry matter yield of ‘Aura’ was 10,535 kg/ha, whereas ‘Kowinearly’ produced 8,422 kg/ha, representing approximately 25% higher productivity. Regional yield performance demonstrated that ‘Aura’ performed particularly well in Cheonan and Jeongeup. In Cheonan, the mean dry matter yield of ‘Aura’ was 12,097 kg/ha, compared with 8,580 kg/ha for ‘Kowinearly’. Likewise, in Jeongeup, ‘Aura’ produced 14,157 kg/ha, which was substantially greater than the 11,129 kg/ha recorded for the control. Yield improvement was also observed in Jinju, although the magnitude was smaller. In Pyeongchang, yield differences between cultivars were minimal, likely because lower temperature conditions limited the expression of yield potential. The superior productivity of ‘Aura’ may be associated with its taller plant height, wider leaves, and longer spikes, which collectively contribute to increased biomass accumulation. In addition, the later heading characteristic of ‘Aura’ may allow an extended vegetative growth period, resulting in greater dry matter production (Barnes et al., 2007;Casler and Van Santen, 2010). The average dry matter yield of ‘Aura’ exceeded 10 t/ha, which is comparable to or slightly greater than the yield levels reported for previously released Korean IRG cultivars (Choi et al., 2000;Ji et al., 2013;Choi et al., 2008;Woo et al., 2023). These findings suggest that ‘Aura’ is a promising medium-maturing IRG cultivar suitable for high forage production under Korean environmental conditions.
4. Feed value
The forage quality characteristics of ‘Aura’ are summarized in Table 4. The CP content of ‘Aura’ was 10.5%, which was considerably higher than the 8.3% observed in ‘Kowinearly’. In contrast, ADF and NDF concentrations were slightly lower in ‘Aura’ (33.5% and 58.2%, respectively) than in ‘Kowinearly’ (34.3% and 59.1%, respectively). As a result, the TDN content of ‘Aura’ was slightly higher at 62.4%, compared with 61.7% for ‘Kowinearly’. Relative feed value (RFV) was also numerically greater in ‘Aura’ (100) than in ‘Kowinearly’ (98), indicating comparable or slightly improved forage quality.
Lower ADF and NDF concentrations are generally associated with improved digestibility and forage value (Undersander et al., 2020). The improved forage quality of ‘Aura’ may be related to its greater leafiness, as leaf tissues generally have higher nutritional value and digestibility than stem tissues (Jung and Allen, 1995). Overall, the forage quality of ‘Aura’ was comparable to or slightly greater than that reported for previously released domestic IRG cultivars (Choi et al., 2008;Woo et al., 2023). Combined with its superior dry matter yield and stable winter survival, these results indicate that ‘Aura’ is a promising domestic IRG cultivar for forage production systems in Korea.
Ⅳ. CONCLUSION
This study was conducted from 2022 to 2024 at the Grassland and Forage Division of the National Institute of Animal Science, Rural Development Administration, to develop a high-yield, medium-maturing IRG cultivar. The newly developed cultivar ‘Aura’ is a tetraploid type with green leaves and exhibits a semi-erect growth habit before winter and an erect growth habit during spring growth. ‘Aura’ showed a heading date of May 11, approximately 10 days later than that of the check cultivar ‘Kowinearly’ confirming its classification as a medium-maturing cultivar. At the heading stage, plant height reached 105 cm, which was approximately 11 cm higher than that of the control cultivar. In addition, spike length, leaf blade width, and spikelet number were greater in ‘Aura’ indicating vigorous growth and high biomass production potential. The average dry matter yield of ‘Aura’ across four regions was 10,535 kg/ha, which was 25% greater than that of ‘Kowinearly’. Furthermore, ‘Aura’ maintained stable winter survival and exhibited improved forage quality, including higher crude protein content and relative feed value. In conclusion, although ‘Aura’ headed later than the check cultivar, it demonstrated superior productivity, stable overwintering ability, and favorable forage quality. Therefore, ‘Aura’ is considered a promising medium-maturing IRG cultivar suitable for forage production across diverse regions of Korea.
