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  • Author or Editor: Margaret E. Daub x
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The use of cell culture techniques for the development of diseaseresistant plants has centered around 3 basic approaches. First of all, pathogen toxins and pathogens themselves have been used to select novel, resistant variants in culture, and such selections have resulted in the isolation of phenotypically and genetically altered plants. Second, cell culture techniques have allowed for the transfer of resistance genes from wild species to agronomically important crops. This approach is limited presently to transfer by protoplast fusion or by ovule and embryo culture, but recent advances in plant transformation techniques may allow for the transfer of genetic information through a suitable vector or through the uptake of isolated DNA some time in the near future. Finally, there is growing evidence that plant cell culture itself can generate stable, heritable variations which are useful for crop improvement.

Open Access

An efficient, high-frequency regeneration and Agrobacterium-mediated transformation system was developed allowing the genetic engineering of three chrysanthemum (Dendranthema grandiflora Tzvelev) cultivars: the formerly recalcitrant and economically important cut-flower mum `Polaris' and two potted mums, `Hekla' and `Iridon'. The regeneration protocol used leaf explants on a sequence of media with four hormone regimes. Explants were first cultured on an embryogenesis-type medium containing a high concentration of 2,4-D, which promoted callus formation. Shoot primordia were induced by culture on medium lacking 2,4-D, followed by shoot elongation on a high-cytokinin plus gibberellic acid medium. Finally, elongated shoots were rooted on a low-auxin rooting medium. Transformed plants of the three cultivars were obtained following co-culture of leaf explants with A. tumefaciens strain EHA 105 harboring the plasmid pBI121 containing genes for neomycin phosphotransferase II (NPTII) and β-glucuronidase (GUS). Stable transformation of the three cultivars was verified via GUS assays and Southern analysis.

Free access