Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/20/2007
Publication Date: 3/19/2008
Citation: Casler, M.D. 2008. Among-and-Within-Family Selection in Eight Forage Grass Populations. Crop Science. 48:434-442. Interpretive Summary: Forage yields have increased little during the 20th century, despite intensive breeding efforts in many species. One reason for this might be the lack of intensive breeding, specifically for increased forage yield, measured on a large number of families and evaluated under proper experimental conditions. Half-sib family (HSF) selection is a common breeding method for forage crops, in which a large number of plants are allowed to open pollinate, seed is harvested on each plant (one "half-sib family" from each plant), then tested in field plots. I conducted selection for increased forage yield in eight forage grass populations and comparing traditional half-sib family (HSF) selection with non-traditional among-and-within-family (AWF) selection. The AWF selection protocol involves digging remnant plants from the best forage plots after they have been evaluated for forage yield for at least 2 years. AWF selection was 2 to 4 times more effective than HSF selection for two grasses that possess rhizomes, but not effective for orchardgrass which does not produce rhizomes. These results suggest that breeders of rhizomatous grasses could improve the efficiency of their selection schemes by using some form of AWF selection.
Technical Abstract: Forage yields increased little during the 20th 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 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 4-yr 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 2 to 4 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 upon some characteristic of the rhizomatous trait of these two grasses.