ERWINIA SOFT-ROT RESISTANCE OF POTATO CULTIVARS TRANSFORMED WITH A GENE CONSTRUCT CODING FOR ANTIMICROBIAL PEPTIDE CECROPIN-B IS NOT ALTERED

Cecropin B is a peptide of approximately 4 kDA which shows antimicrobi al activity in vitro against Gram positive and Gram negative bacteria. Potato cvs Agria, Bintje, Karnico, Kondor and Producent were transfor med with a gene construct encoding a cecropin B precursor polypeptide. In total, 49 independent transgenic potato clones were obtained, Nort hern blot analysis of these plants revealed that the introduced gene w as transcribed to detectable levels in almost all plants, the highest transcription level being approximately 0.6% of total mRNA. No cecropi n B peptide could be detected in transgenic plants, probably as a resu lt of rapid proteolytic degradation of newly synthesized cecropin B by potato endogenous proteases. Neither small tubers of a group of Il cl ones with moderate to high transcription levels nor slices from field grown tubers of any of the transgenic clones obtained, showed signific antly (P<0.01) less rot after inoculation with Erwinia carotovora subs p atroseptica or E. chrysanthemi, the plant pathogenic bacteria that c ause potato soft rot.