Effects of Competition upon the Productivity of White Clover‐Perennial Ryegrass Mixtures. Genetic Analysis

Abstract

AbstractA diallel cross amongst four contrasting white clover varieties was used to provide genetic information on those characters which affect the productivity of white clover‐perennial ryegrass mixtures when grown under a cutting‐only management regime. Generally speaking those characters recorded on the clover families and in mixtures exhibited highly significant additive and non‐ad dative genetic effects, though for1 sortie characters the latter could not be ascribed solely to dominance effects. For two of the clover characters, stolon and leaf number, the genetic picture was radically altered in mixtures by the effects of inter‐specific competition Pseudo‐genetic effects were also detected for the grass characters, bur it was suggested that the two ryegrass varieties used here were exhibiting phenotypic plasticity. As a group the four intra‐varietal crosses performed significantly better than the six intra‐varietal crosses for all clover and mixture characters. Only one of the inter‐varietal crosses had significantly positive specific combining ability effects for most characters and that was between the two long established varieties ‘S. 184’ and ‘S. 100’. The implications of these results for the breeding of white clover varieties for use in mixtures are briefly discussed.