In Vitro Regeneration of Triploid Plants of Euonymus alatus ‘Compactus’ (Burning Bush) from Endosperm Tissues

Euonymus alatus (Thunb.) Sieb., commonly known as ''burning bush,'' is an extremely popular landscape plant in the United States as a result of its brilliant showy red leaves in fall. However, E. alatus is also seriously invasive because of its prolific seed production and effective seed dispersal by birds. Thus, development of sterile, non- invasive, seedless triploid E. alatus is in high demand. In this article, we report successful production of triploid E. alatus using endosperm tissues as explants. In our study, '50% of immature endosperm explants and 14% of mature endosperm explants formed compact, green calli after culture in the dark for 8 weeks and then under light for 4 weeks on Murashige and Skoog (MS) medium supplemented with 2.2 mM BA and 2.7 mM a-naphthaleneacetic acid (NAA). Approximately 5.6% of the immature endosperm- derived calli and 13.4% of mature endosperm-derived calli initiated shoots within 8 weeks after they were cultured on MS medium with 4.4 mM benzyladenine (BA) and 0.5 mM indole-3-butyric acid (IBA). Eighty-five percent of shoots rooted after culture on woody plant medium (WPM) containing 4.9 mM IBA for 2 weeks and then on hormone- free WPM medium containing 2.0 gL -1 activated charcoal for 4 weeks. Eight indepen- dently regenerated triploid plants have been identified. Triploid plant regeneration rates observed were 0.42% from immature endosperm explants and 0.34% from mature endosperm explants, respectively, based on the number of endosperm explants cultured. Because triploid plants cannot produce viable seeds, and thus are sterile and non-invasive, some triploid E. alatus plant lines reported here can be used to replace the currently used invasive counterparts. Chemical names used: benzyladenine (BA), indole-3-butyric acid (IBA), and a-naphthaleneacetic acid (NAA).