Embryogenic callus induction from leaf explants of the Liliaceous ornamental plant, Agapanthus praecox ssp orientalis (Leighton) Leighton -: Histological study and response to selective agents

Highly embryogenic callus cultures were established from leaf explants in the Liliaceous ornamental plant, Agapanthus praecox ssp. orientalis (Leighton) Leighton, as the first step toward the development of an efficient transformation system. Embryogenic calli were induced and then maintained by monthly subculturing onto a medium containing 1 mg l(-1) picloram. Upon transfer to a plant growth regulator-free medium, the calli produced numerous somatic embryos, most of which could develop into plantlets. Histological observations revealed that, following the transfer of the embryogenic calli to a plant growth regulator-free medium, 2- to 6-cell proembryos, probably of unicellular origin, were produced, which passed through the globular and oval stages, and developed into club-shaped embryos with cotyledon, shoot apex and radicle. For establishing an efficient selection system in future transformation, the effects of selective agents (kanamycin, 6418, hygromycin and bialaphos) as well as antibiotics for eliminating Agrobacterium (carbenicillin and cefotaxime) were examined on the growth and development of the embryogenic calli. Callus growth was completely inhibited by 50 mg l(-1) hygromycin or 4 mg l(-1) bialaphos, and somatic embryo formation was completely inhibited by 50 mg l(-1) hygromycin, 75 mg l(-1) G418 or 3 mg l(-1) bialaphos. On the other hand, carbenicillin and cefotaxime rather promoted both growth and development of the embryogenic calli. (C) 2002 Elsevier Science B.V. All rights reserved.