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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.

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We have developed an efficient method for transformation and regeneration of plants from carnation, Dianthus caryophyllus L. Whole leaves from in vitro shoot cultures were mixed with Agrobacterium, cocultivated for 5 days and then plated on 2 #g/1 chlorsulfuron (CS). Regenerated shoots and shoot clusters were divided into smaller sections and plated on 3 #g/1 CS for selection to produce fully transformed shoots. Geneticin (G418) and kanamycin used were not as effective selective agents as CS. All regenerated shoots were vitrified. These were normalized, rooted and transferred to the greenhouse. 100~'o ®enerated plants were transformed based on rooting assay, GUS assay, PCR and Southern analysis.

Hypocotyl‐derived callus from the Helianthus annuus L. inbred line SS415B regenerated significantly more plants if the seedlings were grown in the light. The difference between light‐ and dark‐grown seedlings was not correlated with differences in seedling ethylene production, but seemed to be due to a difference in sensitivity to ethylene at a specific time during seedling growth. Treating 3‐day‐old dark‐grown seedlings with 10 μM aminoethoxyvinylglycine (AVG) effectively inhibited ethylene production for at least 7 days. Hypocotyl callus derived from AVG‐treated seedlings gave the same amount of regeneration as callus from light‐grown seedlings. Promotion of regeneration by AVG was not seen unless the 3‐day‐old seedlings were grown for 4 additional days prior to culturing hypocotyl explants. The effects of AVG could be reversed by treatment with 1‐aminocyclopropane‐1‐carboxylic acid (ACC) during these 4 days. After the 4 days, ACC was no longer effective.

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