BIOLOGICAL CONTAINMENT OF POTATO (SOLANUM-TUBEROSUM) - OUTCROSSING TOTHE RELATED WILD-SPECIES BLACK NIGHTSHADE (SOLANUM-NIGRUM) AND BITTERSWEET (SOLANUM-DULCAMARA)

The biological containment of the potato (Solanum tuberosum) was asses sed by establishing the crossability of this tuberous crop with the re lated wild non-tuberous species in The Netherlands, black nightshade ( S. nigrum) and bittersweet (S. dulcamara). To circumvent crossability barriers, genotypes with different ploidy number were employed and cro sses were performed under different environmental conditions. S. dulca mara was shown to be incongruent with potato at all ploidy levels, whi le S. nigrum displayed unilateral incompatibility. If S. nigrum was em asculated and used as female, fertilization by potato pollen resulted in berry set and seed development. Emasculation of S. nigrum was essen tial in this cross, because analysis of the fertilization process demo nstrated that this species is highly self-compatible and potato pollen was outcompeted by pollen of S. nigrum. The hybrid seeds derived from this cross did not mature and appeared not to be viable. By applicati on of the technique of embryo rescue of immature embryos, hybrid plant s could be obtained. However, these hybrid plants proved to be sterile . These data demonstrate that gene flow by pollen dispersal from potat o to its most common wild relatives in Western Europe is highly unlike ly. The potato is thus a naturally contained species in this part of t he world.