We are finding DMV in many dahlia samples. The symptoms range from
none, occasional chlorotic spots to severe mosaics (Fig. ). The
virus is a sphere 50 nanometers in diameter containing one circular
double stranded DNA molecule about 8000 bases long. It is similar
to viruses such as cauliflower mosaic virus, figwort virus and carnation
etchring virus and therefore belongs in the Caulimoviridae family
of viruses. At one time DMV was considered to be a strain of cauliflower
mosaic virus but our work shows that it is a distinct and different
virus. We have cloned and sequenced a strain of DMV. It contains
6 genes which is typical of a caulimovirus (Fig. ). Genes code for
virus movement between plant cells, aphid transmission, membrane
binding, virus particle structure, a reverse transcriptase needed
for DNA replication and a gene of unknown function. Viruses that
code for a reverse transcriptase replicate use the enzyme for their
replication via an RNA intermediate structure. This enzyme and type
of replication are features of viruses more commonly found infecting
animals. Although DMV does not also infect animals, it is possible
that pharmasutical drugs that are used to treat animal viral infections
may be effective against DMV. We will be looking at chemotherapy
as a means to free dahlias of DMV.
