The use of random amplified polymorphic DNA (RAPD) for hybrid detection in Scirpus from the river Schelde (Belgium)

Along the unique freshwater tidal zone of the river Schelde (Belgium), plants of Scirpus species occur primarily in small and fragmented populations. The majority of these are native Scirpus lacustris, S. pungens, S. triqueter; S. tabernaemontani and intermediate morphological forms. The distribution area of S. triqueter is even restricted to this tidal habitat. However, several cultivated S. tabernaemontani strains have recently been introduced. The latter species is often used to stabilize riverbanks. To determine the existing genetic diversity among these species, stems from plants from 44 different locations were subjected to random amplified polymorphic DNA (RAPD) analysis, using 22 decanucleotide primers. Data analysis of the amplified DNA fragments enabled us to unambiguously differentiate among these Scirpus taxa. Hybridization between S. triqueter and S. tabernaemontani was documented, and the studied hybrids were always genetically more similar to S. triqueter than to S. tabernaemontani. Among the introduced clones, at least two different origins could be distinguished. Several of the introduced S. tabernaemontani clones were clearly different from individuals of the same species that were native to this region. As there were different hybrid genotypes owing to different hybrid events or to introgression, this complex should be safeguarded from genetic pollution. New S. tabernaemontani genotypes with markers not previously observed in that hybrid complex of the unique tidal freshwater habitat should be avoided in replantation projects.