Yield stability and forage quality of Festulolium cultivars across six environments in Central Anatolia: an AMMI and GGE biplot approach

Genotype × environment interaction (GEI) is a key determinant of cultivar performance in perennial forage systems, yet stability data for Festulolium under semi-arid continental climates remain scarce. This three-year study (2022–2024) evaluated yield stability, forage quality, and adaptability of five Festulolium cultivars grown under irrigation at two contrasting locations (Ankara, Kayseri) in Central Anatolia, Türkiye. A randomized complete block design with four replications was used, and stability was assessed through Additive Main Effects and Multiplicative Interaction (AMMI), Genotype plus Genotype × Environment (GGE) biplot, Eberhart–Russell regression, AMMI Stability Value (ASV), and Genotype Selection Index (GSI). Plant height, crude protein, acid detergent fiber, neutral detergent fiber, Ca, K, Mg, P, fresh forage yield, dry matter yield (DMY), and crude protein yield were determined. Environment was by far the dominant source of variation (~ 96% of the treatment sum of squares for the yield traits); the pooled genotype × environment interaction was not statistically significant for the yield traits but AMMI concentrated it in a significant first interaction principal component (IPCA1), whereas for the forage-quality traits (crude protein, ADF, NDF) GEI was statistically significant. GGE biplot analysis identified Achillis as the highest-yielding cultivar, whereas Perseus (ASV = 22.7) and Lofa (ASV = 31.8) showed the lowest interaction with the environment. Eberhart–Russell regression revealed broad adaptability for Lofa (bi = 1.07) and Perseus (bi = 1.03), while Achillis (bi = 1.13) responded strongly to favorable environments. Achillis and Lofa are recommended on the basis of their combined mean dry matter yield and ASV-based stability. Most macromineral concentrations met ruminant requirements, with K reaching 4.30% at Kayseri; Mg, however, declined to ~ 0.09% by the third year at Kayseri, falling below the commonly accepted adequacy threshold and indicating a possible need for supplementation. These patterns reflect strong environmental control over forage mineral composition. Achillis and Lofa are recommended for irrigated Festulolium production in Central Anatolia.