2018 ASHS Annual Conference

Cornus florida (flowering dogwood) is a small tree native to eastern North America that is commonly planted as an ornamental because of its showy bracts and fall color. Its genome has been sequenced, providing information that could be useful for improving horticultural traits like disease resistance. We investigated somatic embryogenesis (SE) as a potential platform for C. florida transformation and gene editing. The induction of SE cultures from immature zygotic embryos of C. florida was reported by Trigiano et al. (1989), but plants beyond the first true leaf stage were not recovered. In prior studies in our lab, we identified the C. florida genotypes and basal medium (WPM) that gave the best SE response from immature zygotic embryos. In the current study, 160 zygotic embryos from the most responsive parent tree were cultured on WPM containing either an auxin analog or no auxin. Zygotic embryos were exposed to eight media treatments (5 embryos/treatment) at four timepoints (globular to early cotyledon stage). We obtained embryogenic lines from explants exposed to IBA (0.1 mg/L), picloram (0.1 mg/L), 2,4-D (2 mg/L), or no auxin. Overall, the SE response rate was 6.9%, with over half of the embryogenic lines originating, surprisingly, on auxin-free medium. For plant development, somatic embryos were transferred to G-7 boxes containing auxin-free WPM supplemented with 0.25 mg/L activated charcoal. To date, 65.4% of the somatic embryos have germinated and 26.9% have developed beyond the first true leaf stage. The effect of a four-week cold treatment (4C) on somatic embryo conversion is being evaluated. Regenerated C. florida plants will be transferred to soil and acclimated to greenhouse conditions.