Plantlet development from immature zygotic embryos of hybrid larch through somatic embryogenesis

Abstract

Embryogenic calli were initiated from immature zygotic embryos of hybrid larch dissected at the precotyledonary stage. Three media were tested, supplemented with 2 mg/l 2,4-dichlorophenoxyacetic acid and 0.5 mg/l 6-benzyladenine. The tissues were formed on all media at frequencies from 3% to 25%. The zygotic origin of calli was confirmed by chromosome counts revealing a diploid number in each of the established lines. Modified Murashige and Skoog (MSG) medium was used for long term maintenance of embryogenic cultures that contained somatic embryos at early developmental stages. The growth rate and morphology of calli were influenced by the type and concentration of the gelling agent. Gelrite gellan gum was superior to Difco-Bacto agar in two of the three tested media when compared at optimal concentrations of 0.4% and 1%, respectively. Further development of somatic embryos was achieved with several treatments. The greatest number of mature embryoids was obtained on MSG with 0.1 mg/l abscisic acid and 0.2 mg/l kinetin for three weeks followed by two subcultures on growth regulator-free medium. The embryoids frequently germinated on the same medium and produced plantlets. Thirty-five plants have been established in soil.