In-vitro culture of fertilized embryo sacs of maize: Zygotes and two-celled proembryos can develop into plants

Fertilized embryo sacs of Zea mays L. surrounded by a few layers of nucellar cells were cultured in vitro. Primary expiants contained zygotes or twocelled proembryos. Embryos of various sizes and shapes were isolated from 12–48% of explants after two weeks of culture in hormone-free media supplemented with 6–12% of sucrose. Many embryos were at the transition or proembryo stages whilst the rest were either differentiated, with a scutellum, a coleoptile and a shoot apex, or had a deformed apical part. Organogenesis started in 36–89% of embryos cultured on a semisolid medium supplemented with coconut water. Most of the embryos formed only roots but up to 9% of embryos regenerated into plants. This simple method leads the way to plant regeneration from in-vitro-manipulated zygotes or proembryos of maize.Abbreviation NBM medium composed of N6 macronutrients, B5 micronutrients and MS vitamins This research was supported by an I.N.R.A. post-doctoral fellowship. The authors thank R. Blanc for donor plant culture, Dr. M. Cock (Reconnaissance Cellulaire et Amélioration des Plantes, Université Lyon 1) for correction of the English and P. Audenis for micrograph development.