Clematis Genetic Diversity and Hybrid Identification using ISSR Markers

Background: Clematis taxa are diverse, with high ornamental value. However, these plants have a complicated genetic background and a long growth period. Thus, molecular identifications are necessary to shorten the breeding cycle. Result: Here, the genetic diversity of 17 parental taxa (five wild species and 12 Texas cultivars) were analyzed using inter simple sequence repeat (ISSR) markers. We obtained 108 alleles using 12 ISSR primers (an average of 9 alleles per primer). Genetic parameters, including the number of alleles (Na), the effective number of alleles (Ne), Nei's genetic diversity (H), and Shannon's diversity (I), suggested that these 17 taxa were highly diverse. Phylogenetic analysis recovered the 17 taxa in two large clades: one cluster included all of the cultivars, as well as Clematis pinnata, C. brevicaudata, and C. tubulosa; the second cluster included C. fusca and C. reticulata . The pairwise genetic distances between all cultivars were 0.421–2.368, suggesting that these cultivars may have derived from closely related species. We next performed five crosses between parental taxa and used ISSR markers to validate the authenticity of the 15 hybrid offspring. ISSR primers amplified bands specific to the male parents of each cross. Male parent-specific bands were identified in 11 of the 15 offspring; these 11 offspring were identified as true hybrids. The remaining progeny were considered self-hybrids due to the absence of male parent-specific bands. Conclusion: Our results demonstrated that ISSR molecular markers may be useful tools for the verification of true Clematis hybrids. ISSR-based genetic diversity analyses, early hybrid identification, and marker assisted selection of Clematis taxa may improve breeding efficiency, excavate key genes associated with important traits, promote the development of new varieties, and shorten the breeding cycle