Induction and Characterization of Tetraploids and Octoploids in Impatiens (Impatiens walleriana)

Impatiens (Impatiens walleriana) is one of the top bedding plants in the United States and is widely used in the landscape, window boxes, and hanging baskets. Commercial impatiens cultivars are diploids with 2n= 16 chromosomes. Little information is available about the effects of polyploidy on the morphology and ornamental values of impatiens. This study was conducted to induce polyploids in impatiens and to determine their morphological differences from diploids. Germinating seeds of ‘Super Elfin Lipstick’ impatiens were treated with colchicine (0.05% to 0.20%) for 2.5 days. Induced polyploids were identified through flow cytometry analysis. A total of 13 solid polyploids (9 tetraploids and 4 octoploids) were found out of 31 plants analyzed. Compared to diploids, impatiens tetraploiods and octoploids exhibited thicker leaves with larger leaf blades. Microscopic observations showed that tetraploids and octoploids had fewer, but larger stomata than diploids did. Tetraploids seemed to produce fewer flowers, and octoploids produced even fewer. Octoploids also showed thicker stems and smaller branching angles, making plants look more upright. Results from this study indicate that induced polyploidy can have profound influence on impatiens’ plant morphology and garden performance.