ERWINIA SOFT-ROT RESISTANCE OF POTATO CULTIVARS EXPRESSING ANTIMICROBIAL PEPTIDE TACHYPLESIN-I

Tachyplesin I is a 2.3 kDa antimicrobial peptide isolated from Southea st Asian horseshoe crabs. Bacterial suspensions containing 1 x 10(6) c olony-forming units/ml of six isolates of pectolytic Erwinia spp., the causal pathogens of potato soft rot and blackleg, were killed in vitr o by 1.4 to 11.1 mu g/ml of tachyplesin I. In an attempt to enhance re sistance to Erwinia spp., each of the potato cultivars Bintje, Karnico and Kondor were transformed with two gene constructs encoding differe nt precursor tachyplesin I proteins under the control of a cauliflower mosaic virus 35S promotor. Northern and western blot analysis showed that the tachyplesin I gene was expressed in transgenic plants. Small tubers of 17 transgenic clones were screened twice for soft rot resist ance to Erwinia carotovora ssp. atroseptica. Under aerobic or anaerobi c conditions, transgenic clones showed slightly less rot than control tubers.