Among-and-within-family selection in eight forage grass populations

Forage yields increased little during the twentieth century, despite intensive breeding efforts in many species. Half-sib family (HSF) and/ or among-and-within-family (AWF) selection methods may overcome this problem. The objective of this study was to compare HSF and AWF selection using forage yield of sward plots as the among-family selection criterion and natural selection of survivors within swards 1: as the within-family selection criterion. Selection for increased forage yield was practiced in eight populations of orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inermis Leyss.), and hybrid wheatgrass [Elytrigia x muctonata (Opiz ex Bercht.) Prokud.]. Two methods of recombination were used: random plants from remnant seed (HSF) or sod cores from selected families four years after establishment (AWF). There were no consistent differences between HSF and AWF selection for orchardgrass, a bunch grass. For the other two species, both highly rhizomatous, AWF selection was two to four times more effective than HSF selection for increasing forage yield. Natural selection within families of the two rhizomatous grasses favored genotypes capable of filling in open spaces left by plant and/or tiller mortality. The consistent differences in selection responses between orchardgrass and the two rhizomatous species suggested that natural selection acted on some characteristic of the rhizomatous trait of these two grasses.