Quantitative Inheritance and Correlations among Forage Yield and Quality Components in Timothy1

Abstract

Forage yield and quality can be improved by breeding only if genetic variance exists within the population. This study was conducted to determine the genetic variability within a population of plants selected at random from a seed lot of ‘Cllmax’ timothy (Phleum pratense L.), to predict the possibility of improving several traits, and to investigate associations among traits. Progeny from diallel crosses of seven sets of six clones each were used to establish field plots. Forage yields were recorded and forage quality characteristics determined for forage from each plot. Significant general combining ability variances were observed for most traits, while specific combining ability variances were significant only for Ca/P ratio and percentage dry matter and Ca. Year ✕ general combining ability variances were significant for some traits, but year ✕ specific combining ability variances were of little or no importance. Narrow sense heritabilities ranged from 0.08 (Pb) to 0.85 (Ca). The genotypicorrelation between forage yield and percentage dry matter was significant and positive. Genotypic correlations between forage yield (and percentage dry matter) and IVDMD, protein, P, and K were negative. The genotypic correlations among IVDMD, protein, P, and K were positive. Most of the other genotypic correlations studied were near zero. Calculated compositions of mixtures of timothy and alfalfa forages are shown graphically. Moderately producing dairy cattle require higher concentrations of most minerals than those contained in timothy forage. Breeding programs making use of general combining ability, such as polycross progeny test, should be used when attempting to improve forage yield and quality of timothy; however, breeding programs should start with a broader based population than found in Climax.