Genetic Diversity of Canadian and Exotic Potato Germplasm Revealed by Simple Sequence Repeat Markers

Canadian potato germplasm ( Solanum tuberosum L.) is unique in its geographic and climatic ranges of adaptation, but little is known about the genetic diversity of the improved Solanum gene pool established over the past century. Simple sequence repeat (SSR) markers were applied to assess the genetic diversity of 114 Canadian and 55 exotic potato accessions. Thirty-six SSR primer pairs were applied and 232 polymorphic bands were scored for each accession. The frequencies of polymorphic bands ranged from 0.01 to 0.98 and averaged 0.35. The proportion of total SSR variation occurring between Canadian and exotic germplasm was 0.6%; among the Canadian cultivars of four major breeding periods 2.7%; among heirloom varieties, modern cultivars and elite breeding lines 4%; and between tetraploid and diploid lines 3.7%. Slightly more diversity was found for exotic, than the Canadian, germplasm. The modern cultivars displayed slightly more diversity than the heirloom varieties and the early cultivars revealed slightly more variation than the recent ones. Clustering 169 accessions revealed more than ten groups, but the groups were not distantly separated. Both the genetically most distinct accessions and the possible genetically duplicated accessions were identified. These findings not only demonstrate the narrow genetic base of the Canadian potato germplasm, but also are useful for managing the existing potato collection and for selecting genetically distinct potato materials to widen the genetic background of the potato gene pool.