Chloroplast DNA identification of eight closely related European salix species

In Austria and southern Europe, Salix alba, S. babylonica, S. fragilis, S. pen- tandra, S. purpurea, S. triandra, S. viminalis and S. vitellina, are found in the same floodplain environment and are known to hybridize. Till now these observations were based on morphological approaches. This study aimed to investigate the phylogenetic relationship of these eight closely related species. Nine polymorphic cpDNA regions representing a total of 5775bp of the large single copy region were sequenced. These results show a clear segregation between the tetraploid and diploid species at the chloroplast level. In the tetraploid species, Salix alba, S. babylonica and S. vitellina form a separate clade showing that S. fragilis and S. pentandra are clearly distant. In the diploid species, S. triandra is distinct from S. purpurea and S. viminalis., The second part of the study was to develop techniques that would allow a rapid screening of numerous samples and a quick and reliable cpDNA identification of the eight species and their haplotypes. Here ten cpDNA primers are made available for these eight Salix species, offering plant breeders, forest manager, taxonomists and population geneticists tools to better understand the complex relationships of hybridization and introgression of willows in Europe.