Submitted to: Southern Nursery Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/12/2009
Publication Date: 12/28/2009
Citation: Rinehart, T.A. 2009. Doubling Chromosomes in Hydrangea macrophylla Cultivars Using Four Different Anti-mitotic Agents. Southern Nursery Association Proceedings 54:365-368.
Interpretive Summary: The existence of multiple triploid hydrangea cultivars can be explained by an tetraploid parent being crossed with diploid parent, most likely within a breeding program, or by the production and of unreduced gametes (2N) that are subsequently fused with normal, haploid gametes (1N). Either or both mechanisms may be responsible for the triploid cultivars currently available since some were developed within breeding programs that may have contained unknown tetraploid parental lines. Alternatively, some diploid Hydrangea macrophylla plants have been shown to produce large, possibly unreduced, gametes at high frequency. The purpose of this study is to establish methods to create tetraploid parental lines and use those lines to confirm the production of new triploid seedlings from crosses with diploid plants.
Technical Abstract: Hydrangea macrophylla cultivars are known to be diploid or triploid, but none of the cultivars examined appear to be tetraploid (Jones et al, 2007; Zonneveld, 2004). Increasing ploidy in woody ornamental plants has been shown to alter the morphology and enhance some ornamental characteristics such as shorter internodes, sturdier stems, and larger flower petals. Some of these traits, along with elongated stomatal guard cells and larger pollen, appear moderately increased in triploid cultivars such as Oregon Pride (Jones et al, 2007). Thus, synthetically producing tetraploid plants by applying anti-mitotic agents to meristematic tissue of known diploid cultivars may be a productive breeding strategy to produce enhanced cultivars. Moreover, tetraploid hydrangeas have potential as breeding lines to produce more triploid cultivars or to better combine genetic backgrounds with wide hybridizations experiments (Reed et al, 2008). Thus far, an effective, rapid method for doubling chromosome number in Hydrangea macrophylla has not been published.