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 antimicrobial activityin vitro against Gram positive and Gram negative bacteria. Potato cvs Agria, Bintje, Karnico, Kondor and Producent were transformed with a gene construct encoding a cecropin B precursor polypeptide. In total, 49 independent transgenic potato clones were obtained. Northern blot analysis of these plants revealed that the introduced gene was transcribed to detectable levels in almost all plants, the highest transcription level being approximately 0.6% of total mRNA. No cecropin B peptide could be detected in transgenic plants, probably as a result of rapid proteolytic degradation of newly synthesized cecropin B by potato endogenous proteases. Neither small tubers of a group of 11 clones with moderate to high transcription levels nor slices from field grown tubers of any of the transgenic clones obtained, showed significantly (P<0.01) less rot after inoculation withErwinia carotovora subspatroseptica orE. chrysanthemi, the plant pathogenic bacteria that cause potato soft rot.