Analysis of genetic relationships in sea buckthorn (Hippophae rhamnoides) germplasm from China and other countries using ISSR markers

Sea buckthorn (Hippophae rhamnoides) is an ecologically and economically important shrub or small tree widely distributed in China, Russia, and Mongolia and its berries are rich in bio-active compounds. Inter-simple sequence repeat (ISSR) markers were used to assess genetic relationships among 78 cultivars and lines of H. rhamnoides ssp. mongolica and hybrids between ssp. mongolica and ssp. sinensis. Thirteen ISSR primers generated 143 bands, 139 (97.2%) of which were polymorphic, with the number of polymorphic bands per primer ranging from 8 - 17. A low coefficient of gene differentiation (0.0588) indicated that genetic diversity existed mainly within populations. Pairwise genetic similarities among the 78 cultivars and lines ranged from 0.362 - 0.939. Cluster analysis indicated that these 78 cultivars and lines could be classified into two groups, in good agreement with their taxonomic classification. Euclidean distances and multi-dimensional scaling confirmed the spatial positions of cultivars and lines of H. rhamnoides ssp. mongolica and its hybrids. We found that line HS22 (of unknown parentage) and cultivar 'CY', with a large fruit trait, had close parental relationships, and that lines TF2-13 and XE2 which shared the same pedigree had a high oil content in their dry pulp. Our data provide a reliable and simple method to identify genetic relationships among cultivars and lines with desirable traits for sea buckthorn breeding programmes.