GENETIC-VARIABILITY FOR LEAF DEVELOPMENT IN PERENNIAL RYEGRASS POPULATIONS

In perennial ryegrass (Lolium perenne, L.), leaf length is a highly he ritable trait likely to respond to both natural and artificial selecti on. The genetic variability of components of leaf morphogenesis of per ennial ryegrass was studied in 2 populations obtained from two cycles of divergent selection for lamina length, in 42 natural populations, a nd in forage and turf cultivars. The genetic progress in the two branc hes of the divergent selection was accompanied by a significant change in the leaf elongation rate, whereas the phyllochron and the leaf elo ngation duration remained relatively unchanged. The forage cultivars w ere not morphogenetically different from the natural populations, and hence progress for yield under infrequent cutting could be made by sel ection for long-leaf populations. Turf cultivars, however, were morpho genetically different from natural populations. Turf cultivars had sma ll leaves with short sheaths and laminae. The population resulting fro m the selection for short leaf had laminae as long as those of turf cu ltivars but with longer sheaths.