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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.
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