BREEDING FOR MANAGEMENT ADAPTATION IN PERENNIAL RYEGRASS (LOLIUM-PERENNE L) .2. GENETIC-VARIABILITY AND HERITABILITY OF LEAF MORPHOGENESIS COMPONENTS

A space-limited experimental design was used for estimating the genetic parameters of growth components in Lolium perenne. These parameters might be taken into account in breeding for yield under a given management. From 58 half-sib families derived from a single polycross, the morphogenesis of 3 successive leaves on 1 tiller of 20 individuals per family was recorded 3 times a week in the spring. Phyllochron, duration of leaf elongation and adult leaf length were measured, and the leaf elongation rate and the mean number of growing leaves per tiller were estimated. Leaf length and elongation rate were found to be highly correlated and showed a genetic variability and a narrow-sense heritability that were definitely higher than phyllochron and duration of leaf elongation. Compared with controls, the progenies indicated an extended genetic variability of morphogenetic traits, mainly towards to genotypes with short leaves and/or rapid phyllochron (but to a lesser extent). Leaf length therefore appeared as the morphogenetic trait that could be most modified through selection. This has been used as a selection criterion in breeding for high productivity under infrequent cutting. Conversely, no morphogenetic trait such as phyllochron, which is assumed to control yield under frequent cutting, responds so effectively to selection, which led us to propose that selecting for short-leaved genotypes could be an alternative approach that should be investigated.