High-Efficiency Somatic Embryogenesis from Seedlings of Koelreuteria paniculata Laxm.

Research Highlights: In the current study, we established a method for plant regeneration via somatic embryogenesis (SE) in Koelreuteria paniculata Laxm. for the first time. Background and Objectives: K. paniculata is an important ornamental and medicinal plant in China. However, the plant has difficulty with asexual reproduction, which imposes a limitation on large-scale propagation. Materials and Methods: Embryogenic calluses were induced from stems of aseptic seedlings on induction media. The effects of different media types and concentrations of N6-benzyladenine (BA), -naphthaleneacetic acid (NAA), and 2,4-dichlorophenoxyacetic acid (2,4-D) on callus induction were examined. Embryogenic calluses were then transferred to Driver-Kuniyuki Walnut (DKW) media containing NAA (0.1-0.2 mg L-1) or 2,4-D (0.5-2.0 mg L-1) to develop somatic embryos. Cotyledon embryos were cultured on DKW media containing NAA (0.1-0.2 mg L-1) until maturation, and were then transferred to 1/2 DKW medium supplemented with 1.0 mg L-1 indole-3-butyric acid (IBA) to produce complete plants. The effects of IBA and NAA on rhizogenesis were then examined by clonal culture. Results: The maximum callus induction frequency (80.25%) was obtained on DKW medium supplemented by 0.5 mg L-1 BA, 0.25 mg L-1 NAA, and 1.5 mg L-1 2,4-D. NAA had a more pronounced effect on somatic embryo growth than did 2,4-D, with a maximum SE frequency (54.75%) observed with 0.1 mg L-1 NAA added to DKW medium. For clonal culture, the highest rooting rate (52%) was observed on 1/4 DKW medium containing 1.5 mg L-1 IBA. Histology studies confirmed the presence of embryogenic calluses and somatic embryos in different stages. Conclusions: This protocol provides a novel method for large-scale propagation of K. paniculata, and creates opportunities for genetic engineering in this species.