Plant regeneration from resistant cells

Table 4. Salt resistance of plants regenerated from cell lines selected for tolerance of salt iir vitro...

Success in regenerating salt-resistant plants from salt-resistant cells has been limited (Table 4). The most extensively quoted example is the work of Nabors et al. (1980) who found that tobacco plants regenerated from NaCl-resistant cell lines survived salinity better than did plants regenerated from unselected lines. The authors themselves were justifiably cautious. 

Figure 9. Somatic cell selection for herbicide resistance. Bottom left, a flask of alfalfa cells in suspension. Top left, addition of herbicide to the cells. Center, cells plated onto solid medium containing herbicide a resistant callus growing on herbicide-containing medium. Top right, resistant plantlets regenerating. Bottom right, tolerant plants selected from tissue culture growing in the field after being sprayed with the herbicide.

Regeneration of plants from the imidazolinone-resistant cell cultures was invariably the most difficult part of the procedure. Cells in culture for long periods of time lose their morphogenic capacity. Imidazolinones may also affect morphogenic capacity. In addition, regenerated plants were often highly or completely sterile. 

The data for this field experiment are summarized in Table 1. Data are presented here for 13 lines which were derived from culture and field-evaluated for resistance to Roundup herbicide. Each of these lines was significantly more tolerant to Roundup than the regenerated non-selected control B74. However, the level of resistance in these 13 cell lines was not commercially significant. Nevertheless, this does indicate that resistant plants can be derived by selections at the cellular level. 

Combination of atrazine resistance and cytoplasmic male sterility in rapeseed. Transfer of atrazine resistant chloroplasts from bird s rape (B. oapestris) into oilseed rape has been accomplished by back-crossTng (s this volume). The purpose achieved by somatic cell fusion was to combine the atrazine-resistant chloroplasts carried by a B. napus line with cytoplasmic male sterility (CMS), a mitoohondrlal tralt (l9). The CMS trait was carried by a B. napus line with the cytoplasm of radish (Raphanus sativus). Since both traits, atrazine resistance and CMS, are maternally inherited in sexual crosses, the only way to combine the traits was by protoplast fusion. The desired atrazine-resistant cybrids were identified in a randomly regenerated sample of plants by the presence of the CMS flower morphology and their darker green color at low temperature. Somatic hybrids rather than cybrids were obtained in each clone since no irradiation had been used to facilitate the elimination of one of the parental nuclei. 

Salisbury, P.A., 1987. Blackleg resistance in weedy crucifers. Cruciferae News Lett. 12, 90. Sigareva, M.A., Earle, E.D., 1999. Camalexin induction in intertribal somatic hybrids between Camelina sativa and rapid-cycling Brassica oleracea. Theor. Appl. Genet. 98,164-170. Sikdar, S.R., Chatterjee, G., Das, S., Sen, S.K., 1987. Regeneration of plants from mest hyll protoplasts of the wild crucifer Eruca sativa Lam. Plant Cell Rep. 6, 486-498. 

---