Genetic diversity of Finnish home garden rhubarbs (Rheum spp.) assessed by simple sequence repeat markers

Rhubarb samples were collected from home gardens all around Finland to study their genetic diversity. Altogether, the study contained 647 samples, of which 539 were from home gardens. In addition, reference cultivars and samples from the Finnish national collection of rhubarb genetic resources located in the Natural Resources Institute Finland (Luke) were included. Six SSRs, which amplified a total of 80 alleles, were used to calculate genetic distances between samples, and a dendrogram was built. The most common cultivar among the rhubarbs from Finnish home gardens (57%) was identical to ‘Queen Victoria’ in the Luke collection. Thirty-eight samples (7%) from citizens were identical to ‘The Sutton’ and ‘Strawberry’, which on the other hand were identical to each other. We detected misidentifications of rhubarb cultivars in our study. Under the same cultivar name there might be different genotypes, for example ‘Victoria’ was very heterogeneous. On the other hand, cultivars with different names may have the same genotype e.g. ‘Strawberry’ and ‘The Sutton’. In addition to providing information about genetic variability of rhubarbs in home gardens, the results of the study were used to update the Finnish national collection of rhubarb genetic resources: to remove duplicates, and to replace accessions of unknown origin with new polymorphic ones with more accurate information of their history. As far as we know, this is the first study where rhubarb samples have been collected widely from home gardens and evaluated with DNA markers.