Cultivars of the aroid genus Dieffenbachia are valued as ornamental plants for their attractive foliage, ease of production, and their durability as living specimens for interior decoration. Since 1980, with the control of flowering and pollination techniques, many commercial Dieffenbachia cultivars have resulted from breeding programs that select for both aesthetics and tolerance of abiotic and biotic stresses (Henny, 2000). To facilitate commercial production, tissue culture methods have been used as a tool for fast and reliable increase of hybridized Dieffenbachia selections.
At least 80 commercial foliage plant cultivars have originated from somaclonal variation in tissue culture propagation (Chen and Henny, 2008). Dieffenbachia × ‘Star Bright M-1’ is a somaclonal variant of a commercial cultivar D. × ‘Star Bright’ (U.S. patent PP9051; Henny, 1995). The M-1 variant was selected out of a population of tissue culture-derived plants because its shorter internodes gave a more compact appearance and the lower leaves were wider than the parent cultivar. In addition, it showed improved adaptability to interior low-light conditions because older leaves were held longer on the plant. A strategy for enhancing plant adaptability to stressful environments is chromosome doubling (Levin, 1983). Gene redundancy leads to genome buffering by increasing allelic diversity (Udall and Wendel, 2006), thus increasing plant tolerance to environmental stress. Polyploid plants can be more robust, have thicker leaves, larger fruit, a greater degree of drought and disease tolerance, improved adaptability, and resistance to environmental stress (Chakraborti et al., 1998; Eeckhaut et al., 2004). Additionally, chromosome doubling may provide an opportunity for novel phenotypic variation resulting from gene duplications (Udall and Wendel, 2006). Thus, an approach to further enhance the adaptability of the M-1 variant to interior low-light conditions could be chromosome doubling. Colchicine is the most widely used chemical agent for chromosome doubling. Tetraploids at frequencies of 83.3% and 80.0% were induced in Xanthosoma sagittifolium when in vitro-grown plants were treated with 1.25 mM or 2.5 mM of colchicine, respectively (Tambong et al., 1998). Colchicine has been reported to induce tetraploidy in nine Zantedeschia cultivars (Cohen and Yao, 1996). Rapidly multiplying in vitro shoot cultures were exposed to 0.05% (w/v) colchicine on solid Murashige and Skoog (MS) media for 1, 2, or 4 d resulting in a recovery of tetraploids ranging from 12.9% to 41.8%. Colchicine along with oryzalin and trifluralin also successfully induced tetraploids of Alocasia micholitziana ‘Green Velvet’ (Thao et al., 2003) and Spathiphyllum wallisii Regal (Eeckhaut et al., 2004). However, chemical induction of polyploidy has not been reported in Dieffenbachia.
The objectives of this study were to use colchicine to induce tetraploids of Dieffenbachia × ‘Star Bright M-1’ in vitro and determine if chemically induced tetraploids were stable and showed better adaptability to low-light conditions for interiorscaping.
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