Genetic variation and trait selection in ryegrass (Lolium multiflorum Lam.) across dry and rainy seasons in Peru

Ryegrass ( Lolium multiflorum Lam.) is an important forage species in Peruvian livestock micro-watersheds; however, increasing climatic variability underscores the need to identify promising germplasm for breeding programs. Twenty-three accessions, including three widely used checks in the area, were evaluated under an augmented block design across three livestock micro-watersheds in the Amazonian Andes of Peru, using mixed linear models with REML/BLUP for the dry and rainy seasons and a combined analysis. The study aimed to determine variance components, Cullis heritability, and correlations across fifteen selected traits, as well as to identify promising accessions through the Elston index and principal component analysis for plant height, basal coverage area, dry matter concentration, crude protein, neutral detergent fiber, and in vitro digestibility. The results revealed significant variation among accessions for most agronomic traits, with the exception of stem diameter. Heritability for in vitro digestibility was zero during the dry season. Plant height, basal coverage area, spike and spikelets number exhibited high heritability (> 0.60) in both seasons, while crude protein showed moderate heritability (dry season = 0.54; rainy season = 0.51). Dry matter concentration displayed high heritability during the rainy season and moderate heritability during the dry season. Principal component analysis indicated greater phenotypic differentiation during the rainy season (73.6%) than during the dry season (58.1%). Furthermore, the Elston index identified LM20 as the most promising accession in the combined analysis and dry season, outperforming the checks. LM5 showed performance comparable to the check varieties, whereas LM18 exhibited the most balanced profile during the rainy season. These findings provide a quantitative foundation for future breeding programs targeting the conditions of the Amazonian Andes.