In Vitro Zygotic Embryo Germination and Somatic Embryogenesis through Cotyledonary Explants of Paeonia lactiflora Pall.

Abstract

A simple and efficient protocol was developed for somatic embryogenesis from the cotyledon explant of Paeonia lactiflora Pall. Seeds of peony obtained from fieldgrown plants were disinfested and zygotic embryos were excised. For germination, excised embryos were cultured on the Murashige and Skoog (MS) medium supplemented with 3% (w/v) sucrose, 0.8% (w/v) agar, and different concentrations of N6 benzyl-adenine (BA) and gibberellic acid (GA3). The greatest germination percentage (95%) was observed when embryos were cultured on the MS medium with 1.0 mg • L-1 BA and 0.5 mg • L-1 GA3, and maintained at 25 ± 2°C under a 16 h photoperiod. Thirty days old cotyledon explants were cultured on the MS medium supplemented with different concentrations and combinations of plant growth regulators viz., BA, GA3, 2,4-dichlorophenoxyacetic acid (2,4-D), and á-naphthalene acetic acid (NAA). After 90 days, the globular embryos were directly formed on the surface of explants. The highest frequency of somatic embryo induction (72.5) was obtained on the MS medium with 3.0 mg • L-1 BA, 1.0 mg • L-1 NAA, 1.0 mg • L-1GA3, and 0.1% (w/v) activated charcoal (AC), with a mean number of 14 embryos per explant. Maturation of globular embryos into heart- and torpedo-shape was observed on the same medium. When the torpedo-shaped embryos were transferred onto the same MS medium supplemented with 3.0 mg • L-1 BA, 1.0 mg • L-1 NAA, 1.0 mg • L-1GA3, and 0.1% (w/v) AC, secondary somatic embryos were observed on the surface of primary somatic embryos. When the embryos were transferred to the MS medium supplemented with 1.0mg • L-1 each of BA and GA3, all of them converted into plantlets, but their growth was very slow.