COMPLEX SEGREGATION ANALYSIS OF GERBERA FLOWER COLOR

The distribution of hue (CIELAB colour notation) classes among flowers of the Davis population of gerbera (Gerbera jamesonii H. Bolus ex Hoo ker) appears bimodal. This suggests that the genetic control of hue is determined by the segregation of a gene with large effect modified by additional genes with smaller effects. Complex segregation analysis ( CSA), routinely employed in human genetic epidemiology, was used to st udy both qualitative and quantitative variation. CSA applies pedigree analysis through the consideration of transmission probabilities to op timize likelihood functions of Various genetic models. Applying this t echnique to study flower hue of a sample representing generations 14, 15 and 16 of the Davis population, allowed identification of a putativ e dominant major gene with genotypic values for the dominant homozygot e, heterozygote and recessive homozygote of 32, 32 and 71 degrees, res pectively. This corresponds to the modes of the hue frequency distribu tion for the population. The putative major gene represents 0.66 of th e total variation. The residual parent-offspring correlation (rho(po)= 0.2) measures the genetic contribution to the remainder of the varianc e.