Genetic variability for leaf development in perennial ryegrass populations

In perennial ryegrass (Lolium perenne, L.), leaf length is a highly heritable trait likely to respond to both natural and artificial selection. The genetic variability of components of leaf morphogenesis of perennial ryegrass was studied in 2 populations obtained from two cycles of divergent selection for lamina length, in 42 natural populations, and in forage and turf cultivars. The genetic progress in the two branches of the divergent selection was accompanied by a significant change in the leaf elongation rate, whereas the phyllochron and the leaf elongation duration remained relatively unchanged. The forage cultivars were not morphogenetically different from the natural populations, and hence progress for yield under infrequent cutting could be made by selection for long-leaf populations. Turf cultivars, however, were morphogenetically different from natural populations. Turf cultivars had small leaves with short sheaths and laminae. The population resulting from the selection for short leaf had laminae as long as those of turf cultivars but with longer sheaths.