Ⅰ. INTRODUCTION
Tall fescue (Festuca arundinacea Schreb.) is a cool-season perennial grass widely used for pasture, hay, and grassland establishment because of its high persistence and broad adaptation to diverse soil and climatic conditions (Buckner et al., 1979). Compared with many other cool-season forage grasses, tall fescue has a deep and extensive root system and can maintain relatively stable stands under environmental stresses such as drought, high temperature, and repeated defoliation. These characteristics have contributed to its widespread use in temperate grassland systems. Tall fescue is also an important forage species for grazing because of its persistence and ability to recover following defoliation. However, as plants mature, leaves and stems become coarser and forage nutritive value may decline substantially (Fieser and Vanzant, 2004). Therefore, plant architecture, maturity, regrowth ability, persistence, and forage nutritive value are important traits in the development of tall fescue cultivars for grazing systems. In particular, a relatively short plant type with good regrowth may facilitate forage utilization under repeated defoliation and grazing conditions. The association between tall fescue and fungal endophytes is another important consideration in cultivar development. Endophyte infection can enhance plant persistence and tolerance to biotic and abiotic stresses. However, some endophyte-infected tall fescue plants produce ergot alkaloids that can adversely affect livestock health and performance, including elevated body temperature, reduced productivity, and reproductive problems (Hohenboken et al., 1991;Bouton et al., 2002). Therefore, the development of endophyte-free cultivars with desirable agronomic and forage characteristics represents an important breeding approach for improving the suitability of tall fescue for forage and grazing systems. In Korea, tall fescue cultivars used for grassland establishment have traditionally depended largely on introduced germplasm. However, introduced cultivars may not always exhibit stable agronomic performance under Korean climatic conditions, which include low winter temperatures and hot and humid summers. Consequently, domestic breeding programs have focused on developing tall fescue cultivars with improved adaptation and agronomic characteristics under Korean environments. Several cultivars have been developed through these breeding efforts, including ‘Greenmaster’, a stress-tolerant and high-yielding cultivar (Choi et al., 2010), followed by ‘Purumi’ (Lee et al., 2012), ‘Greenmaster2ho’ (Lee et al., 2015), ‘Greenmaster3ho’ (Lee et al., 2016), and ‘Greenmaster4ho’ (Lee et al., 2018). These cultivars have expanded the genetic resources available for domestic tall fescue breeding and grassland establishment. For grazing-oriented grassland, however, maximizing harvested biomass is not the only breeding objective. A short plant type, good regrowth after defoliation, resistance to lodging, favorable disease response, persistence, and high forage nutritive value are also desirable characteristics. In particular, maintaining a relatively short and vegetative canopy may contribute to efficient forage utilization under repeated grazing. Therefore, breeding tall fescue cultivars that combine these agronomic characteristics with endophyte-free status is important for the development of grazing-oriented grassland systems in Korea. Through these breeding efforts, a new tall fescue cultivar, ‘Hugreen’, was developed with a short plant type, good regrowth, favorable forage nutritive characteristics, and endophyte-free status for grazing and grassland establishment. ‘Hugreen’ is currently under application for plant variety protection with the Korea Seed and Variety Service (KSVS). Therefore, this study was conducted to describe the breeding process of ‘Hugreen’ and to evaluate its morphological and agronomic characteristics, regional adaptability, dry matter productivity, forage nutritive value, disease response, and endophyte status in comparison with the commercial cultivar ‘Fawn’.
Ⅱ. MATERIALS AND METHODS
This study was conducted from 2015 to 2023 by the Forages Production Systems Division of the National Institute of Animal Science (NIAS), Rural Development Administration (RDA), to develop a new tall fescue (Festuca arundinacea Schreb.) cultivar with short plant stature, high forage quality, and disease resistance for grazing and grassland establishment in Korea.
1. Selection of superior lines and development of the synthetic population
The tall fescue (Festuca arundinacea Schreb.) cultivar ‘Hugreen’ (breeding line Fa 20ho) was developed through the selection of superior vegetative lines followed by population crossing. The breeding program began in 2015 with artificial crosses and the collection of tall fescue ecotypes to establish diverse breeding materials. In 2017, five superior vegetative lines, 17XFa07, 17XFa26, 17XFa29, 17XFa38, and 17XFa64, were selected based on their morphological and agronomic characteristics. These selected lines originated from the crosses 15Fa32 × 15Fa65, 15Fa15 × 15Fa78, 15Fa03 × 15Fa52, 15Fa50 × 15Fa59, and 15Fa16 × 15Fa40, respectively. In 2018, the five selected lines were subjected to population crossing for seed synthesis, and the resulting synthetic population was designated Fa 20ho. Fa 20ho was subsequently advanced to preliminary yield and agronomic evaluation during 2020–2021 and was selected as a promising breeding line for further regional adaptation testing (Fig. 1).
2. Evaluation of agronomic characteristics of ‘Hugreen’
A yield trial of the tall fescue (Festuca arundinacea Schreb.) breeding line ‘Hugreen’ (Fa 20ho) was conducted from 2020 to 2021 at the experimental field of the Forages Production Systems Division, National Institute of Animal Science (NIAS), Rural Development Administration (RDA), Republic of Korea. The agronomic and morphological characteristics of the breeding line were evaluated according to the standard guidelines for tall fescue cultivar characterization established by the Korea Seed and Variety Service (KSVS).
3. Regional adaptability trials
Regional adaptability trials of the tall fescue breeding line ‘Hugreen’ (Fa 20ho) were conducted for three consecutive years from 2021 to 2023 at four locations in Korea: Cheonan, Pyeongchang, Jinju, and Jeju. ‘Fawn’ was used as the check cultivar to evaluate the regional adaptability, agronomic characteristics, and forage productivity of ‘Hugreen’. Seeds were sown at a rate of 30 kg/ha in rows spaced 20 cm apart. Fertilizer was applied at N–P2O5–K2O rates of 80–200–70 kg/ha in the establishment year and at annual rates of 210–150–180 kg/ha from the second year onward. During the maintenance period, nitrogen was split into four applications, with 30% applied in early spring, 30% after the first harvest, 20% after the second harvest, and 20% after the third harvest. Phosphorus and potassium were each applied in two equal portions, with 50% applied in early spring and the remaining 50% after the third harvest. Agronomic characteristics, including heading date, plant height, leafiness and regrowth were evaluated during the growing season. Morphological characteristics were primarily evaluated at Cheonan, whereas forage productivity was determined at all four trial locations. Dry matter yield was calculated as the sum of four harvests per year at each location.
4. Analysis of forage nutritive value
The forage nutritive value of the tall fescue cultivar ‘Hugreen’ was evaluated using standardized laboratory procedures. Crude protein (CP) content was determined by the Kjeldahl method according to AOAC (1990) using an automated nitrogen analyzer (Kjeltec™ 2400 Autosampler System, Foss Tecator, Sweden). Acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents were determined using an ANKOM Fiber Analyzer (ANKOM Technology, Macedon, NY, USA) according to the procedures described by Goering and Van Soest (1970). In vitro dry matter digestibility (IVDMD) was determined using the two-stage digestion method of Tilley and Terry (1963), as modified by Moore (1970). Total digestible nutrients (TDN) were estimated from ADF concentration using the equation , as described by Menke and Huss (1980). Forage samples collected at the first harvest were used for the nutritive value analysis
5. Detection of endophyte infection
Endophyte infection in ‘Hugreen’ was determined using mature seeds. Seed samples were analyzed using a Phytoscreen Seed Endophyte Detection Kit (Agrinostics Ltd. Co., Watkinsville, GA, USA; Cat. No. ENDO7971) according to the manufacturer’s instructions. The presence or absence of endophyte infection was determined based on the reaction obtained from the assay. ‘Hugreen’ was confirmed to be endophyte-free.
6. Statistical analysis
Data were subjected to statistical analysis using SAS software (ver. 9.4; SAS Institute, Cary, NC, USA). Differences between cultivar means were tested by Student’s t-test, with significance thresholds set at p<0.05.
Ⅲ. RESULTS AND DISCUSSION
1. Agronomic characteristics of ‘Hugreen’
The major morphological characteristics of ‘Hugreen’ and ‘Fawn’ are presented in Table 1. ‘Hugreen’ is a hexaploid cultivar with dark-green leaves and a semi-erect growth habit. The flag leaf was 13.1 cm long and 6.3 mm wide, whereas those of ‘Fawn’ were 14.6 cm and 7.4 mm, respectively. The length of the longest stem was 79.5 cm in ‘Hugreen’, approximately 21 cm shorter than that of ‘Fawn’ (100.5 cm). Inflorescence length was also shorter in ‘Hugreen’ (15.0 cm) than in ‘Fawn’ (18.9 cm). These morphological characteristics indicate that ‘Hugreen’ has a more compact plant architecture than ‘Fawn’. Shorter stems may be useful in grazing-oriented cultivars where maintaining a relatively low pasture canopy and stable stand structure is desirable.
2. Heading date and plant height
The mean heading date of ‘Hugreen’ across four locations and three years was May 9, approximately six days later than that of ‘Fawn’, which headed on May 3. Thus, ‘Hugreen’ was classified as a medium-maturing tall fescue cultivar. Plant height showed a clear difference between the two cultivars. The mean plant height of ‘Hugreen’ was 52.2 cm, whereas that of ‘Fawn’ was 73.3 cm. Thus, ‘Hugreen’ was approximately 21.1 cm shorter than the control cultivar (Table 2). The consistently shorter plant height observed across trial locations represents one of the most distinctive characteristics of ‘Hugreen’. In grazing systems, canopy management requires a balance between efficient forage utilization and the retention of sufficient leaf area and carbohydrate reserves to support regrowth and sward persistence (Raeside et al., 2012). Thus, short plant stature combined with adequate regrowth may be advantageous for maintaining a relatively uniform pasture canopy. However, grazing preference and animal performance were not evaluated in the present study, and these potential advantages should therefore be confirmed through subsequent grazing trials.
3. Dry matter yield performance
The dry matter yields of ‘Hugreen’ and ‘Fawn’ across four locations from 2021 to 2023 are shown in Table 3. The mean dry matter yield of ‘Hugreen’ was 12,093 kg/ha, corresponding to approximately 80% of the 15,072 kg/ha recorded for ‘Fawn’. The relative yield of ‘Hugreen’ ranged from 73% at Cheonan to 93% at Jeju. The lower dry matter production of ‘Hugreen’ appears to be associated, at least in part, with its compact morphology and substantially shorter plant height. The difference in plant stature between ‘Hugreen’ and ‘Fawn’ is also evident in Fig. 2. Therefore, ‘Hugreen’ differs from previously developed tall fescue cultivars selected primarily for high biomass production, such as ‘Greenmaster’ (Choi et al., 2010). Although its dry matter yield was lower than that of ‘Fawn’, the breeding value of ‘Hugreen’ should be considered in relation to its compact stature and favorable forage nutritive characteristics rather than biomass yield alone. Together, these characteristics suggest that ‘Hugreen’ has potential for grazing-oriented grassland establishment in Korea.
4. Forage nutritive value
The forage nutritive characteristics of ‘Hugreen’ are summarized in Table 4. At the first harvest, ‘Hugreen’ had a CP content of 13.4%, while ‘Fawn’ had 9.4%. IVDMD reached 76.9% in ‘Hugreen’ and 68.4% in ‘Fawn’. ‘Hugreen’ had an NDF content of 56.4%, compared with 61.5% in ‘Fawn’. ADF showed the same pattern, with values of 28.3% in ‘Hugreen’ and 32.6% in ‘Fawn’. In contrast, TDN was higher in ‘Hugreen’ at 66.6% than in ‘Fawn’ at 63.2%. When these findings are considered together with the lower dry matter yield of ‘Hugreen’ (Table 3), they indicate that the greater biomass production of ‘Fawn’ did not correspond to superior forage nutritive value at the first harvest. A similar relationship between herbage mass and forage quality was reported in a two-year rotational sheep-grazing study of endophyte-free tall fescue cultivars, in which ‘Festorina’ and ‘Kentucky 31’ produced more herbage, whereas ‘Roa’ and ‘Johnstone’ were generally higher in forage quality (Vecellio et al., 1995). For additional context, the CP content of ‘Hugreen’ was similar to the 13.6% reported for ‘Greenmaster’, whereas its IVDMD was higher and its NDF and ADF contents were lower than the corresponding values reported for that cultivar (Choi et al., 2010). This comparison should be interpreted cautiously because ‘Hugreen’ and ‘Greenmaster’ were evaluated in separate trials. Nevertheless, the direct comparison with ‘Fawn’ indicates that ‘Hugreen’ has a favorable forage nutritive profile, supporting its intended use in grazing-oriented grassland systems.
5. Endophyte status of ‘Hugreen’
Endophyte infection in mature seeds of ‘Hugreen’ was examined using a Phytoscreen Seed Endophyte Detection Kit according to the manufacturer’s instructions. No detectable endophyte infection was observed in the tested seeds, confirming the endophyte-free status of ‘Hugreen’ (Fig. 3). The absence of detectable endophyte infection is an important characteristic of tall fescue cultivars intended for forage and grazing use. Endophyte infection in tall fescue can contribute to increased plant persistence and tolerance to environmental stresses. However, some endophyte associations produce toxic alkaloids that can adversely affect livestock health and performance (Hohenboken et al., 1991;Bouton et al., 2002). Therefore, the endophyte-free status of ‘Hugreen’ is particularly relevant to its intended use in grazing systems, as it avoids the potential livestock-related risks associated with toxic endophyte-infected tall fescue.
Ⅳ. CONCLUSION
A new tall fescue (Festuca arundinacea Schreb.) cultivar, ‘Hugreen’, was developed by the National Institute of Animal Science, Rural Development Administration, Republic of Korea. Five selected breeding lines, 17XFa07, 17XFa26, 17XFa29, 17XFa38, and 17XFa64, were combined through population crossing in 2018, and the resulting breeding population was designated Fa 20ho. Regional adaptation trials were conducted at Cheonan, Pyeongchang, Jinju, and Jeju from 2021 to 2023.
‘Hugreen’ is a hexaploid, medium-maturing cultivar with dark-green leaves and a semi-erect growth habit. Its mean heading date was May 9, approximately six days later than that of ‘Fawn’. Mean plant height was 52.2 cm, which was 21.1 cm shorter than that of ‘Fawn’. The mean dry matter yield of ‘Hugreen’ was 12,093 kg/ha, corresponding to 80% of that of ‘Fawn’. However, ‘Hugreen’ showed favorable forage nutritive characteristics, with CP, IVDMD, NDF, ADF, and TDN values of 13.4, 76.9, 56.4, 28.3, and 66.6%, respectively. In addition, ‘Hugreen’ was confirmed to be endophyte-free. These characteristics suggest that ‘Hugreen’ is a short-statured tall fescue cultivar potentially suitable for grazing and persistent grassland establishment in Korea.
