Cotton Regeneration

Abstract

The perception of the value of regeneration of any crop plant via somatic embryogenesis has evolved over the last one and a half decades. In the early eighties, somaclonal variation produced during the embryogenesis process was touted as being of significant value to plant breeding. And indeed, various positive agronomic attributes have been identified, stress tolerance, herbicide tolerance, earlier fruiting habits, disease resistance, etc. Protoplast fusion, followed by regeneration, as a means of making wide crosses was also touted as a benefit, as was the possibility of artificial seeds (Ammirato, 1987). During this period, Fraley et al. (1983) and Horsch et al. (1984) demonstrated that Agrobacterium could transfer foreign genes to plant cells and whole plants regenerated that express the foreign gene. With gene transfer demonstrated, the attention turned to somatic embryogenesis as a vehicle for making transgenic plants. However, somaclonal variation proved to be undesirable when a true-to-type transgenic plant was the ultimate target. Obtaining a true-to-type tranformant remains problematic in many species when somatic embryogenesis is the vehicle for transformation. Additionally, somatic embryogenesis has proven to be highly genotype dependent in most of our most important agronomic crop species. Cotton is among those (Trolinder and Xhixian, 1989).