Analysis of Genetic Diversity and Relationships in the China Rose Group

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.