Regeneration of Plants from Cotton Protoplasts

Abstract

Protoplasts are recognized to be ideal for genetic transformation as direct DNA transfer mediated via polyethylene glycol, electroporation or microinjection can result in transgenic plants (see Bajaj 1996). Agrobacterium- mediated transformation and particle bombardment of target tissue followed by regeneration through somatic embryogenesis, and particle bombardment of shoot tips are the techniques used to transform cotton (Firoozabady et al. 1987; Umbeck et al. 1987; Finer and McMullen 1990; Perlak et al. 1990; Bayley et al. 1992; McCabe and Martineil 1993, also see Chaps. V.1–3, this Vol.). Both techniques, however, have some limitations. Indeed, the regeneration through somatic embryogenesis is genotype-dependent (Trolinder and Chen 1989). Therefore only Gossypium hirsutum L. cv. Coker could be transformed, resulting in time-consuming and laborious backcrossing to introduce the novel characteristic of transgenic Coker into commercial cultivars. Alternatively, meristem transformation is genotype-independent, but transformation frequency is very low (0.001%; McCabe and Martinell 1993). Also, because frequency of chimera formation is high, meristem transformation is not appealing. Transformed protoplasts offer the prospect of producing nonchimeric plants, as they regenerate from a single cell. The single-cell origin of regenerated plants is also useful in the development of mutants with valuable characteristics resulting from somaclonal variation or from induced mutagenesis during tissue culture.