DIFFERENTIATION OF ISOLATED WHEAT ZYGOTES INTO EMBRYOS AND NORMAL PLANTS

Efficient and reproducible embryo development has been obtained from f ertilized wheat (Triticum aestivum L.) egg cells isolated 3-6 h after hand-pollination of emasculated spikes. It is possible to routinely is olate viable zygotes from about 75% of the excised ovaries from cultiv ars of both winter and spring types. Go-culture with barley microspore s which had been stimulated to sporophytic development resulted in emb ryonic development of the cultivated wheat zygotes. Within 23 h of pol lination; the zygotes underwent their first cell division. They procee ded to develop into club-shaped embryos, most of which turned subseque ntly to dorsiventral differentiation. The morphological patterns of in -vitro-grown embryos were in accordance with those of normal zygotic e mbryos growing in planta. The formation of twin or multiple embryos or iginating from a single zygote was dependent on genotype and exogeneou sly supplied auxin. Upon transfer onto a suitable solidified medium, z ygote-derived embryos usually germinated and developed into plants. Af ter optimizing the feeder system, the nutrient medium and the concentr ation 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 morphologicall y normal and fertile. The in-vitro development from isolated zygotes o f a higher-plant species into typically patterned zygotic embryos is s hown here for the first time. Since the entire process, including earl y zygotic development, is now freely accessible to observation and mic romanipulation, the method presented opens up new approaches in fundam ental as well as applied fields of reproductive biology.