Inheritance of concentration of water-soluble carbohydrates in cocksfoot

The concentration of water-soluble carbohydrates (WSC) of cocksfoot is lower than that of other temperate grasses. Increasing the WSC concentration in cocksfoot is important in increasing its digestibility and preference by ruminants. The genetic variation in mono- and disaccharides, fructans and total WSC concentrations and their inter-relationships with crude protein (CP) and fibre concentrations of cocksfoot (Dactylis glomerata L.) at the vegetative growth stage in half-sib cross populations were assessed in two experiments conducted under spaced planting and sward conditions. There was a wide range in the means for concentrations of fructan, WSC and neutral-detergent fibre (NDF) in parents and progeny whereas there was a narrow range of the means for concentrations of mono- and disaccharides, CP and acid-detergent fibre (ADF). Mean concentrations of mono- and disaccharides showed the smallest range. Mean squares of entries in parents and progenies were significant for mono- and disaccharides, fructan and total WSC concentrations in all populations. The entry × year interactions for fructan and total WSC concentrations were significant in the parents and the half-sib progeny. However, the entry × year interactions for mono- and disaccharide concentrations in progeny were not significant. Concentration of WSC was under genetic control as mean squares of the concentration values were significant and variance components for all traits were significantly larger than zero. There were negative genetic correlations between WSC and ADF and NDF concentrations. Narrow-sense heritabilities (hn) estimated from variance components of progeny for total WSC concentrations were 0·59 and 0·53 in sward and spaced planting conditions respectively. The hn of fructan and WSC concentrations were similar in both sward and spaced planting conditions, whereas that of mono- and disaccharide concentrations varied from 0·20 to 0·69. It was found that the genetic variation of the total WSC concentration in cocksfoot depended mainly on genetic variation in fructan concentration. These results suggested that the forage quality of cocksfoot at the vegetative growth stage was influenced by an additive gene effect and could be improved genetically by recurrent selection.