Utilizing Somatic Embryogenesis to Segregate Tissue Color Chimeras in Prunus serrulata 'Royal Burgundy'

‘Royal Burgundy’ flowering cherry (Prunus serrulata) arose as a somatic mutation (branch sport) from the popular cultivar ‘Kwanzan’. ‘Royal Burgundy’ has desirable reddish-purple foliage color, but appears to be a chimeral mutation with periodic adventitious shoots frequently reverting to green foliage. Regenerating plants from a single or small number of cells through somatic embryogenesis has the potential to isolate this desirable mutation in a homogeneous condition. The objective of this study was to develop a somatic embryogenic protocol for P. serrulata ‘Royal Burgundy’ and to regenerate plants that are stable for purple foliage. Induction of embryogenic callus from leaf tissue was investigated using Murashige and Skoog medium supplemented with auxins 1-naphthaleneacetic acid (NAA), 2-4-dichlorophenoxyacetic acid (2,4-D), indole-3-acetic acid (IAA), or picloram at concentrations of 1.25, 2.5, 5, 10, or 20 µM. Somatic embryogenesis was obtained from all auxin types with 2.5 – 10 µM 2,4-D producing the greatest number of somatic embryos per plate (~1-3 embryos). In a second study, the effect of 2,4-D and the polyamine putrescine on embryogenic callus and embryo formation was investigated. Murashige and Skooge medium was supplemented with a factorial combination of 2,4-D (1.25, 2.5, 5, and 10 μM) and putrescine (0.125, 0.25, 0.5, and 1.0 µM). There was a significant interaction between 2,4-D concentration and putrescine concentration where the combination of 2.5 µM 2,4-D and 0.5 µM putrescine produced the highest number of embryos per plate (~6 embryos). Somatic embryos were grown, elongated and rooted in vitro before being transferred to the green house. Recovered plants are being evaluated for expression and stability of purple foliage.