The inheritance of patterned white flowers in zonal pelargoniums

White flowered cultivars have petals which are either pure white, or patterned white with coloured markings localized within clearly defined zones on the upper surface of the petals. Five patterns are identified. The bar pattern has pigment localized within a small zone on both sides near the base of each of the lower triplet of petals. The centre pattern has a V-shaped coloured zone in the basal half of all petals filling in the centre of the flower. The picotee pattern colours the edges of all petals. The ring pattern is a coloured zone running across the basal half of all petals. The vein pattern consists of two prominent coloured veins running from the base of the upper pair of petals. The expression of these patterns is controlled by the dominant alleles of four genes: the bar, picotee and vein patterns by the genes Baiba, Celce or PH pi, and Ve/ve respectively, and the centre and ring patterns by the interaction of the products of two genes Ce with Ve and Ba with Ve respectively. The homozygous recessive states of these genes are epistatic to the red- marking gene, Rm/rm, responsible for controlling the synthesis of anthocyanin pigments that fill the marked zones. Other colour marking genes are probably responsible for variations in colour, especially pink which was a frequent alternative to red. In the absence of the colour marking genes, the pattern zones may sometimes become lightly pigmented from other sources providing the pattern gene itself is present. The zones are considered to be areas of pigment accumulation rather than centres for pigment synthesis.