Breeding perennial ryegrass (Lolium perenne. L) for improved quality traits is an important step towards improving animal performance. The objectives of this research were to determine the extent and nature of genetic variability for organic matter digestibility and water soluble carbohydrates.Near Infrared Spectroscopy (NIR) was used for estimation of the quality traits. NIR calibrations were developed using standard measurements. For this purpose the samples were analyzed in the laboratory for digestibility (pepsin cellulase gammanase) and water soluble carbohydrates (HPLC). The results of 1 cycle divergent selection for digestibility indicate that at the vegetative growth stage the genetic variability for this character was low and response asymmetrical. For water soluble carbohydrates, genetic variability was larger and selection response again asymmetrical. The asymmetry of response was attributed to
directional dominance and/or segregation at a few loci with large effects.
Estimation of broad sense heritability from clonally propagated genotypes were
higher than narrow sense heritability from offspring/parent regression (h2b=
0.54 to h2 op= 0.32 for digestibility and h2b= 0.67 to h2 op= 0.35 for water soluble
carbohydrates). Because of asymmetry of response these estimates are not useful in predicting genetic gain for increased level of either traits. The genetic and phenotypic correlation between traits was high (rp = 0.48 to 0.70 and rg = 0.56 to 0.77).
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