Divergent Selection for Leaf Width, Length and Growth Rate in Two Annual Ryegrass (Lolium Multiflorum Lam.) Cultivars

Abstract

Annual ryegrass (Lolium multiflorum Lam.) is a winter annual forage of considerable importance to the southeastern United States, with limited use in the northwestern and midwestern United States. Annual ryegrass is one of eight species of Lolium and of these eight species is surpassed only by perennial ryegrass (1. perenne L.) in use (Terrell, 1968). Annual ryegrass is normally planted into a prepared seed bed or drilled into dormant warm season sod and can be grazed in as little as two months following planting (Miller , 1984; Riewe and Mondart, 1985) . Improvement of dry matter yield is one of the more important objectives in any forage breeding program (Sleper, 1977). Most plant breeders, however, have depended upon indirect selection for improving dry matter yield due in part to ease of measurement (Wilson, 1981). With annual ryegrass indirect selection is particularly important since, in measuring total seasonal yield, the seed crop is necessarily destroyed preventing any recurrent phenotypic selection. Also, due to the difficulty in creating clones of annual forages, clonal selection for yield is not practical. Indirect selection relies upon the identification of forage yield component traits. Traits which have been suggested as effective indirect selection criteria for forage yield include tillers per plant.