Assessment of genetic variation in black poplar in Ireland using microsatellites.

Abstract

Ireland represents the most northwesterly limit of the distribution range of black poplar (Populus nigra L.). The objective of this study was to increase the understanding of genetic variation in the species in Ireland by using a species-specific marker and seven microsatellite markers to determine the accuracy with which morphological methods can distinguish between black poplar and the introduced hybrid poplar, P. x euramericana and the degree of clonal reproduction which has occurred in the past. In addition, hairiness of the leaf petiole was assessed to determine whether the Irish black poplar trees sampled were members of the subspecies betulifolia. A total of 117 black poplar trees were sampled in spring 2003 by taking distal sections of twigs, preferably with healthy flowering buds, from the crowns and standing them in water in the lab until bud burst. Samples were taken from trees believed to be black poplar from counties Dublin, Kildare, Offaly, Tipperary and Galway. The species-specific molecular marker indicated that almost a third of the sampled trees were P. x euramericana which had been misidentified as P. nigra. There was considerable clonal duplication such that only nine genotypes were present in the 80 P. nigra samples that were DNA tested. These results indicate that considerable vegetative propagation had occurred in the past. The majority of the black poplar belonged to the sub-species betulifolia.