Phenotypic recurrent selection for intensity of petal color in red clover

The inheritance of flower petal color intensity in red clover (Trifolium pratense L.) was investigated by phenotypic recurrent selection. Seven cycles of selection changed the mean color from pink to purple, i.e., from 3.1 to 8.2 on a scale of 2 to 9 in which 2 is light pink and 9 is purple. Additive genetic variance per cycle ranged from 0.088 to 0.246 and was higher in the earlier cycles than in the later cycles of selection. Narrow-sense heritability was greatest in cycle 2 when total variance was high and in cycle 7 when fixation of the purple color was approached. Regression on orthogonal polynomials indicated that the increase in color score was quadratic, the response per cycle in later cycles being significantly less than in the early cycles. Cycles also differed significantly in weight per plant indicating a linear response owing to inbreeding depression unrelated to color score. The number of genes involved in the inheritance of petal color intensity was estimated to be about 25, obviously not simply inherited.