Analysis of Genetic Diversity and Relationships in the China Rose Group
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The wild origin, early breeding history, and diversity of the China Rose group, including R. chinensis and its varieties, cultivars, and hybrids, are largely unknown. The aims of this study were to investigate the genetic diversity and relationships of the China Roses with related species and hybrids, including information in support of, or refuting, the hypothesis that these roses are the hybrid result of the wild R. chinensis var. spontanea and R. odorata var. gigantea. Ninety Rosa accessions, including China Roses, a Miscellaneous Old Garden Rose, Noisettes, early Polyanthas, Bourbons, Teas, and species from Sections Indicae and Synstylae were surveyed using 23 microsatellite primer pairs. The trnH-psbA chloroplast intergenic spacer was also sequenced for the China Roses, Misc. Old Garden Rose, and the species to look specifically at maternal relationships. A total of 291 alleles were scored for the 23 microsatellites, with alleles per locus ranging from 6-22 and averaging 12.65. A dendrogram based on Dice similarity and a three-dimensional Principle Coordinate Analysis (PCoorA) graph were plotted with the data. In the cluster analysis, the similarity coefficients ranged from ~0.15-0.99, with the cultivated roses forming well-defined groups at about 0.45 similarity. These groups generally reflected the American Rose Society horticultural classifications. A large number of sports and synonyms in the China Rose group were identified through this analysis as well. The PCoorA gave a better graphical representation of the relationships of the species and cultivars, and with the inclusion of the chloroplast sequence haplotypes, some maternal relationships could also be identified. This study shows that the cultivated China Roses are a closely related group and identified which accessions were likely Hybrid China Roses. The results also suggest that the China Roses were maternally derived from R. chinensis var. spontanea. Based on the microsatellites and chloroplast sequence haplotypes, the identity of the R. odorata var. gigantea accessions in this study are suspect, but the China Roses may also have this species in their background as the result of natural or artificial hybridization.
