Hybridisation between chocolate cosmos and yellow cosmos confirmed by phylogenetic analysis using plastid subtype identity (PSID) sequences

摘要

Chocolate cosmos has chocolate-coloured flowers with a scent of chocolate, and leaves like miniature dahlias. Chocolate cosmos is endangered in its native Mexico. It has been classified ambiguously as Cosmos atrosanguineus or Bidens atrosanguinea. We have resolved the phylogenetic relationship of chocolate cosmos among the genera Cosmos, Bidens and Dahlia by an analysis of plastid subtype identity (PSID) sequences. PSID sequences showed that chocolate cosmos has a closer relationship with Cosmos than with Bidens or Dahlia. Based on this finding, chocolate cosmos was open-pollinated with two Cosmos species, C. bipinnatus and C. sulphureus. We successfully produced a hybrid plant with C. sulphureus using embryo rescue. The hybrid plant showed an intermediate phenotype such as crimson-red flowers. Its hybrid nature was confirmed by DNA fingerprinting and flow cytometric analysis.