Selection for and Heritability of Stolon Characteristics in Two Cultivars of White Clover

Abstract

White clover (Trifolium repens L.) herbage production in intensively grazed pasture is related to clover stolon growing point density. High stolon density is associated with small leaf size. The objective of this study was to examine the probability of breaking the genetically controlled link between leaf size and stolon density by manipulating internode length and branching propensity. Two white clover cultivars, Grasslands Tahora and Grasslands Kopu, were grown in two New Zealand environments, full sunlight or 50% sunlight (shade), during 1991 and 1992. Selections were made for high or low frequency of stolon branching, long or short stolon internodes, and large or small leaves. These selections were polycrossed within groups to give 24 lines. Lines were evaluated in pots grown outside to determine the effect of selection on these and other shoot characters. Selection of populations with high or low frequency of branching gave progeny with different frequency of branching for all cultivar‐environment combinations except for selection within Tahora grown in shade. Selection of populations with long or short internode length gave progeny with different internode length in all cultivar‐environment combinations. Selection for large and small leaflet width gave progeny with different leaflet width in all cultivar‐environment combinations except for selection within Kopu grown in sun. Two estimates were made of narrow sense heritabilities. Estimates from mid‐parent versus progeny regression heritabilities were higher for internode length and leaflet width than for frequency of branching. Realized heritabilities were again generally higher for internode length and leaflet width than for frequency of branching although there were some exceptions. Selection for high frequency of branching in Tahora grown in full sunlight had a high realized heritability. Stolon characters, such as internode length and frequency of branching, can be effectively manipulated by selection. The degree of selection success can be affected by environment and cultivar. Selection for variation in internode length is likely to be more successful than for frequency of branching.