Response to divergent selection for stolon characters in white clover (Trifolium repens)

Stolon death, often caused by grazing or winter-kill, is a major factor determining the survival and persistence of white clover (Trifolium repens L.), the most important forage legume in UK agriculture. Since stolon morphology apparently affects stolon survival, this study was designed to assess the genetic variation for stolon characters within a white clover population from Switzerland and to assess the effects of two generations of selection for stolon characteristics on that population. Bidirectional selection was carried out simultaneously for stolon diameter (as the primary criterion of selection) and total stolon length i.e. the product of the length of the longest stolon and stolon number. Four selection lines were established: (a) plants with thick sparse stolons, (b) plants with thick profuse stolons, (c) plants with thin sparse stolons and (d) plants with thin profuse stolons. Realized heritabilities for stolon diameter, estimated in both directions and over both generations of selection, were found to lie within the range 0.28-0.44; significant shifts in population means for stolon diameter were demonstrated. Selection for thin profuse stolons and for thick sparse stolons was effective, but because of negative correlations between stolon diameter and both stolon length and number, selection for thin sparse stolons or thick profuse stolons was ineffective.