Resistance responses to Phoma lingam of plants regenerated from selected cell and embryogenic cultures of haploid Brassica napus.

Resistant plants and plants with reduced susceptibility against the pathogen Phoma lingam could be regenerated from selected callus and embryogenic cultures of haploid rape (Brassica napus) previously treated with mutagens. In the two in vitro selection systems used - absence of fungus growth on the cultures after incubation with parasite spores and resistance to the toxic filtrate - the resistance to the toxin was effective. In addition, some regenerants with increased tolerance were obtained from unselected cultures. Resistance tests on regenerated plants were carried out by inoculation of whole plants in the greenhouse, reproducing as much as possible the infection mechanisms which take place under natural conditions. Preliminary results on resistance of the progeny of single susceptible and tolerant regenerants seem to indicate that the acquired resistances are of a genetic nature.