ABSTRACT
The genome structure and organization of a new and distinct caulimovirus that is widespread in dahlia (Dahlia variabilis) was determined. The double-stranded DNA genome was ca. 7.0 kb in size and shared many of the features of the members of the genus Caulimovirus, such as the presence of genes potentially coding for the movement protein, the inclusion body protein, and the reverse transcriptase (RT), and an intergenic region consisting of a potential 35S promoter. However, the virus differed from the previously described dahlia mosaic caulimovirus and other known caulimoviruses in that the aphid transmission factor (ATF) was absent and the putative coat protein contained a C-terminal deletion and was fused in-frame with the RT. Sequence identity at the amino acid level with known caulimoviruses including a previously reported caulimovirus from dahlia was low and ranged from 32 to 72%. The absence of an ATF and the highly divergent nature of the genomic sequence are characteristics of this new caulimovirus that is widely associated with dahlia.
Subject(s)
Caulimovirus/classification , Caulimovirus/genetics , Dahlia/virology , Genome, Viral/genetics , Plant Diseases/virology , Viral Proteins/genetics , Amino Acid Motifs , Amino Acid Sequence , DNA, Viral/genetics , Molecular Sequence Data , Open Reading Frames , Phylogeny , Sequence Analysis, DNA , Species Specificity , Viral Nonstructural Proteins/geneticsABSTRACT
Dahlia mosaic, caused by Dahlia mosaic virus (DMV), is one of the most important viral diseases of dahlia. Molecular characterization of DMV showed the association of two distinct caulimoviruses (DMV-D10, DMV-Portland) and a D10-like sequence variant (DMV-Holland) with the disease. Using primers specific to these two viruses and the sequence variant, a polymerase chain reaction-based assay was used to determine their relative incidence in several dahlia samples from the United States and the Netherlands. Testing was done on samples collected in 2005 and 2006 in the United States and in 2006 in the Netherlands. Results indicated the predominance of DMV-D10 over DMV-Portland and DMV-Holland in both the United States and the Netherlands. Using conserved regions of the viral genome, primers were designed and used to detect all three sequences. Results suggested that DMV-D10 is predominantly associated with dahlia mosaic, but diagnostics should also include testing for DMV-Portland and DMV-Holland.
ABSTRACT
Dahlia is an economically important ornamental crop in the United States and several other countries in the world. Among the viral diseases that affect dahlia, Dahlia mosaic virus (DMV) is considered to be the most widespread and to have the greatest impact on flower production. Using grow-out tests followed by polymerase chain reaction (PCR)-based testing of the seedlings, dahlia seed obtained from three different sources were shown to contain DMV. Additionally, the distribution of DMV in various parts of the dahlia seed was determined by PCR. Growout tests revealed a high rate of seed transmission. DMV was detected in cotyledons and, rarely, in the seed coat. The virus also was detected in pollen collected from infected plants. In addition to vegetative propagation, seedborne infection could be contributing to the spread of DMV in dahlia. Use of virus-free seed and vegetative material would result in reduced incidence of the disease.
