Induction, Regeneration and Characterization of Tetraploids in Caladium

Caladium is an ornamental aroid commonly used in containers, hanging baskets and gardens for its long-lasting colorful foliage. This study was conducted to induce tetraploids and to assess their values for caladium breeding. Leave segments of 'Tapestry', a fancy-leaved caladium cultivar with large pink blotches on leaves, were treated with colchicine and cultured in vitro to regenerate plantlets. Out of 445 plantlets regenerated and established in the greenhouse, 82 showed variation from the control plants in leaf shape, color, and/or thickness. These variants were analyzed for nuclear DNA contents, and 50 plants were found to be tetraploids. The highest rate of tetraploid induction was 31.7% and occurred in the treatment where leaf segments were cultured in 0.2% colchicine for 4 d. Morphological characterization revealed that tetraploids had much smaller leaf length/width ratio, longer stomata but lower stomata densities, thicker petioles, thicker leaves, and thicker main veins, compared to their diploid counterparts. The remaining 32 variants were found to be diploids, but their nuclear DNA contents varied to some extent, which may indicate potential chromosomal changes in these variants. Several types of leaf coloration pattern changes were observed on these variants. Results from the present study suggest that induced tetraploidy can result in significant morphological changes in caladium, thus it can be a valuable tool in caladium breeding.