Modification of flower color in florist's chrysanthemum: production of a white-flowering variety through molecular genetics

Chimeric chalcone synthase (CHS) constructs were prepared in both anti–sense and sense orientations, and introduced into the chrysanthemum cultivar Moneymaker, along with a T–DNA vector lacking a CHS construct. For both the anti–sense and sense constructs, the majority of the plants produced pink flowers typical of Moneymaker itself. Of 133 sense and 83 anti–sense transgenic individuals, 3 of each set produced fully white or very pale pink flowers. No white–flowering transgenic plants were obtained in control transformations. The white flowers were found to accumulate higher levels of chalcone synthase precursors and to have reduced levels of chalcone synthase message. A small–scale field trial was performed to evaluate the stability of the phenotype throughout a series of vegetative propagation steps and during plant growth. The white–flowering trait was maintained well through vegetative propagation; however, during growth of individual white–flowering plants, some pink color was found in some flowers. At one site 2% of the white–flowering plants produced a few pink flowers; at two other sites, as many as 10–12% of the plants produced pale pink flowers.