Differentiation of isolated wheat zygotes into embryos and normal plants

Efficient and reproducible embryo development has been obtained from fertilized wheat (Triticum aestivum L.) egg cells isolated 3-6 h after hand-pollination of emasculated spikes. It is possible to routinely isolate viable zygotes from about 75% of the excised ovaries from cultivars of both winter and spring types. Go-culture with barley microspores which had been stimulated to sporophytic development resulted in embryonic development of the cultivated wheat zygotes. Within 23 h of pollination; the zygotes underwent their first cell division. They proceeded to develop into club-shaped embryos, most of which turned subsequently to dorsiventral differentiation. The morphological patterns of in-vitro-grown embryos were in accordance with those of normal zygotic embryos growing in planta. The formation of twin or multiple embryos originating from a single zygote was dependent on genotype and exogeneously supplied auxin. Upon transfer onto a suitable solidified medium, zygote-derived embryos usually germinated and developed into plants. After optimizing the feeder system, the nutrient medium and the concentration of 2,4-dichloro phenoxyacetic acid (2,4-D), more than 80 and 90% of the zygotes eventually developed into plants in genotypes Florida and Veery #5, respectively. All regenerated plants were morphologically normal and fertile. The in-vitro development from isolated zygotes of a higher-plant species into typically patterned zygotic embryos is shown here for the first time. Since the entire process, including early zygotic development, is now freely accessible to observation and micromanipulation, the method presented opens up new approaches in fundamental as well as applied fields of reproductive biology.