CEREAL PROTOPLASTS

In cereals for a long time regenerable protoplasts could be isolated from embryogenic suspension lines, initiated from callus cultures of immature zygotic embryos or microspores. Up to now they still represent the main source for totipotent protoplasts and meanwhile it is possible to obtain protoplast-derived transgenic plants. Since suspension cultures are difficult to handle and regeneration capacity is restrained by somaclonal variation, research has focused on methods for protoplast isolation and culture circumventing long in vitro culture periods. Recently, culture systems with a reduced in vitro phase prior protoplast isolation have been developed providing totipotent protoplasts. Successful protoplast regeneration could be demonstrated from selected primary callus cultures of somatic and androgenic cell origin. A further step avoiding a previous callus culture was achieved by the direct isolation of embryogenic protoplasts from microspore cultures and mesophyll protoplasts from leaf tissue of seedlings. With the regeneration of protoplasts of in vivo and in vitro produced zygotes today the spectrum of protoplasts able to regenerate has been extended. Furthermore, these systems allow the regeneration of plants with somatic, androgenetic or zygotic background. In this article we will give an overview on the difficult explant sources and protoplast systems and their application in biotechnology.