Genetic variation for fodder yield and quality in half sib families of perennial ryegrass (Lolium perenne) grown as spaced plants and swards

The objective of this research was to study the genetic variation for total dry matter yield and three quality characteristics: digestible organic matter in dry matter (DOMD), water soluble carbohydrate (WSC) and crude protein content (CP) in perennial ryegrass (Lolium perenne) under spaced plants and swards conditions. A polycross nursery containing 24 genotypes were established. Prior to planting, each parent was vegetatively propagated to give 8 clones. At harvest, seeds of propagated clones of each genotype was combined. Both seed of half sib families and their clone propagated parents were grown as spaced plants and sward over two years. Near Infrared Spectroscopy (NIR) was used to estimate the quality parameters. The broad sense heritability estimates (h2b) were relatively high for quality traits (h2b = 0.48-0.80), but moderate for dry matter yield (h2b = 0.25-0.49). Narrow sense heritability (h2n), was low for dry matter yield (h2n=0.03-0.26) and high for quality traits (h2n= 0.03-0.92). Genetic analysis indicated that non-additive genetic variance was the major component controlling DM yield, while, additive genetic variance was more significant for quality traits. The genotypic correlation of DOMD and WSC was significantly positive, while the relationship of CP with WSC was significantly negative. These results were consistent over two years. None of the phenotypic or genotypic correlation estimates of DOMD and CP were significant. DM yield and DOMD were negatively correlated under swards. The genetic correlation of DM yield with WSC was positive, however, its relationship with CP was negative.