Taxonomic Relationships of Rosa

The genus Rosa has been classified into 4 subgenera.  They are:

  • Rosa
  • Platyrhodon
  • Hesperhodos
  • Hulthemia

This classification system is in accordance with Bean (1970) and is the most widely accepted classification system.  Rosa contains 11 sections, whereas the other subgenera are monotypic.

Presently, R. roxburghii is classified in the subgenera Platyrhodon.  It's taxonomic position was based on morphological characteristics.  Unfortunately, environmental factors influence a plants phenotype.

Successful crosses between R. roxburghii and R. bracteata have been reported.  This is an indication that a close relationship between R. roxburghii exists with any species within the subgenera Rosa.

Our lab has researched R. roxburghii and its hybrids using isozymes, RAPDs, karyotyping, and in situ hybridization.  The following is a summarization of our findings.

Isozymes:
    Forty-seven Rosa species from subgenera Rosa and Platyrhodon were analyzed on starch gel electrophoresis.  The enzymes there were studied were ACP, MDH, PGI, and 6PGD.  The isozyme dendrogram groups subgenus Platyrhodon within subgenus Rosa.

RAPDs:
    Thirty-seven Rosa species from subgenera Rosa and one species each from subgenera Hesperhodos and Platyrhodon were analyzed using 213 randomly amplified polymorphic DNA markers with 10 primers.  Data was used to construct a phenogram.  Analysis groups R. roxburghii within subgenus Rosa.

Karyotypes:
    Representatives from all four subgenera were assessed for mitotic chrmomosome numbers.  Cluster analysis grouped Platyrhodon within subgenus Rosa.

Florescent in situ hybridization (FISH):
    Four diploid species plus one cultivar (R. chinensis, R. odorata, R. x fortuniana, R. roxburghii Tratt., and Angel Face) were subjected to FISH.  In each of theses roses a single large rDNA locus appeared at the tip of a chromosome.  The uniform presence and position of a single locus suggested karyotypic stability and possibly close relationship among the species examined.