Genetic studies of the pattern of floral pigmentation in clarkia gracilis

Abstract

The flowers of Clarkia gracilis subsp. sonomensis have large petals each with a large, central, red-purple spot while the flowers of subsp. gracilis are small and unspotted. Other pigmentation (anthocyanin) patterns also vary within and between these subspecies. We carried out a genetic analysis of differences in floral patterns and petal size. A novel basal petal spot appeared in the F2. The analysis indicated that the novel petal spot was specified by an allele in subsp. gracilis at a locus governing spot position. This allele is not normally expressed in subsp. gracilis because of the action of a modifier gene at a second locus. The study also indicated single factor inheritance for presence versus absence of pigmentation on the hypanthium, stamens, and the lower portion of the petals. Multifactorial inheritance was observed for differences in petal length and width. Most of the possible recombinant floral patterns were recovered in the F2 and F3. This system can be used to study developmental regulation of floral traits as well as ecological relationships between floral pattern and pollination system. The recovery of a normally unexpressed allele for basal petal spot points to the difficulty of extrapolating from phenotypic analysis to an understanding of morphological evolution. © The Genetical Society of Great Britain.