Cell Culture Manipulations as a potential breeding tool.

Protagonists of plant tissue and cell culture methods are now commonplace. Applications of these techniques can be found in nearly every field of plant science and they have resulted in many valuable contributions to· our knowledge of primary and secondary metabolism, the cell cycle, the regulation of growth and differentiation, and plant/micro-organism interactions. From the agricultural point of view the obvious attractions of tissue culture methods for virus eradication and rapid clonal propagation of commercial varieties have continued to draw a great deal of attention and the number of species for which the basic culture criteria have either been met, or are under intensive study, is now quite extensive (43). Interest in genetic manipulations of plant cell cultures has continued to increase, despite the many obstacles in the way of wide application of these methods. It is therefore expected that those interested in overcoming low temperature stress would also direct some attention to these genetic manipulations. This review will consider the different methods for genome modification in cell cultures and the problems encountered in the application of these methods. The extent to which these problems have been and can be overcome will be evaluated with particular reference to experiments performed with crop species, and having a potential for crop improvement. In addition the limited progress which has been made in breeding for chilling resistance using tissue cultures will be considered