The 2009 ASHS Annual Conference

Modern rose hybrids owe their origins in large part to traits inherited from the China Roses, most notably, the everblooming character (Shepherd, 1978).  However, the wild origins, early breeding history, and diversity of the China Rose group, including R. chinensis and its varieties, cultivars, and hybrids, is largely unknown.  Twenty-three microsatellite markers were used to survey the genetic diversity and relationships among the China Roses, their early hybrids, and select species from sections Indicae and Synstylae.  The utility of the intergenic chloroplast spacer trnH-psbA in Rosa was also tested to obtain information on the maternal lineage of the China Roses.           

The SSR data clustered the rose accessions into groups, which in most cases agreed with the horticultural classification of the accessions (according to Modern Roses IX).  The early Tea roses were the exception. These fell into a large group along with roses classified as Hybrid Chinas, Noisettes, Bourbons, and Polyanthas, all with either unknown parentage or a Tea rose(s) in the recorded parentage.  One accession of R. odorata var. gigantea from China was also included in the Tea cluster.  The remainder of the roses from the China, Noisette, and Bourbon classes formed separate clusters, while the remainder of the Polyantha roses clustered with accessions of R. multiflora, one of the parent species of that hybrid class.  The results also support, or disagree with, the recorded parentage or ‘sport’ status listed for a number of the cultivars, and give identity to several ‘found’ roses being grown under new names.  Preliminary results from the chloroplast spacer sequence show 100% amplification and good variability, which should prove useful for tracing maternal lineages.