Allelic Nature of Two Carnation Variants 1-Aminocyclopropane-1-carboxylate (ACC) Synthase Genes, DcACS1a and DcACS1b

We found a variant in the carnation genome, the 1-aminocyclopropane-1-carboxylate synthase gene (DcACS1) that had only DcACS1b, suggesting it is a homozygote of the gene in the carnation cultivars ‘Skyline’ and ‘Scarlett Plus’. The ‘Mini-tiara’ carnation is obtained by an interspecific cross between carnation and wild pink, one of which, Dianthus knappii. D. knappii, had three ACS1 genes orthologous to DcACS1b; i.e., DkACS1b.1, DkACS1b.2, and DkACS1b.3. The composition of ACS1 homologs was analyzed in sub-cultivars of the ‘Mini-tiara’ carnation by PCR amplification of intron 1, intron 2, and 3'-UTR. Each sub-cultivar of the ‘Mini-tiara’ carnation had two ACS1 genes with various combinations. ‘Mini-tiara 0707’ had only DcACS1a, suggesting it is a DcACS1a/DcACS1a homozygote. ‘Mini-tiara Topaz’ had DcACS1a and DcACS1b, ‘Mini-tiara Ruby’ had DcACS1a and DkACS1b, and ‘Mini-tiara Lilac’ had DcACS1b and DkACS1b.2. These findings suggest that the ‘Mini-tiara’ carnation has two genes from a virtual group of at least five ACS1 gene homologs of carnation and D. knappii. The discovery of a DcACS1b homozygotic carnation and inheritance of ACS1 homologous genes in the ‘Mini-tiara’ carnation from carnation and D. knappii suggests the allelic nature of carnation DcACS1a and DcACS1b genes.