EFFECT OF SELECTION UNDER CULTIVATION ON MORPHOLOGICAL TRAITS AND YIELD OF LADINO WHITE CLOVER LANDRACES

One reason for the relatively low genetic advance realized in forage l egumes may be the possible selection, under the severe intraspecific c ompetition occurring naturally during cultivation, of a few high-yield ing genotypes that would be of similar value in a broadly-based landra ce or old cultivar and a narrowly-based, modern variety. The effect of selection under cultivation was assessed in two Ladino white clover f arm landraces. Genotypes collected from each farm after a three-year c rop cycle (survivor populations), or obtained from the seed used to es tablish each meadow (original populations), were multiplied clonally a nd evaluated in isolation and monoculture conditions for one year. The occurrence of directional selection was observed only in the landrace featured by greater intra-population variation in favour of genotypes with longer petioles (+11%), larger leaf size (+13%), less stolons (- 14%) and lower production of heads (-16%). Selection for the first two traits would imply an increase of competitive ability, whilst that fo r the fourth trait appeared mainly as a correlated response. The trade -off between leaf gigantism and head production could act as a bufferi ng mechanism against rapid change in genotype frequencies following ra ndom mating. A slight trend towards directional selection for higher y ield (+6%) in the same landrace was not statistically significant. No disruptive or stabilizing selection was observed for any trait in eith er landrace.