BREEDING FOR MANAGEMENT ADAPTATION IN PERENNIAL RYEGRASS (LOLIUM-PERENNE L) .1. ASSESSMENT OF YIELD UNDER CONTRASTING CUTTING FREQUENCIES AND RELATIONSHIPS WITH LEAF MORPHOGENESIS COMPONENTS

The potential yield under contrasting cutting frequencies was assessed among 18 diploid or tetraploid varieties of perennial ryegrass and 53 half-sibs progenies from a broad-based polycross. Simultaneously, a s urvey of the genetic variability of leaf morphogenesis components was carried out among the varieties. Both among varieties and progenies, t he yield appeared to be negatively correlated between cutting frequenc ies and, compared with progenies, varieties were generally found to be more productive under infrequent cutting than under frequent cutting. Diploid and tetraploid varieties were discriminated only by morphogen etic traits related to tiller size and leaf elongation, as expected, w ith some association with the yield under frequent cutting and tiller density in the plots under the same management. The results suggested that there was a potentially high productivity under frequent cutting which should be considered but seemed to be systematically countersele cted by plant breeders, probably due to the procedure of assessment of varieties for registration.