PHYTO MEDIZIN Mitteilungen der Deutschen ... - Die DPG

consists of ~1800 bp with an ORF (nt 119-1579) encoding a putative CP with
487 aa. Both sequences show high homology on amino acid level to the
RdRp and CP of White clover cryptic virus (WCCV), respectively. In addition,
some conserved motifs observed in RdRps of some ssRNA and dsRNA
viruses were also identified in the RdRps of VCV and WCCV.
A new potyvirus causing flower breaking in Begonia semperflorens
I Bouwen and R van der Vlugt; Wageningen University and Research Centre, Plant
Research International BV, Wageningen
Flower colour breaking was found in red and pink flowering cultivars of
Begonia semperflorens. The leaves of plants with these flower symptoms
sometimes showed a vague mottling. After testing plant material in ELISA
for the presence of different viruses there was only a positive reaction with a
general monoclonal directed against potyviruses. Examination of crude extracts
of leaves and flower petals in the electron microscope revealed no virus
particles. It was also not possible to transmit a virus mechanically to indicator
plants. The extreme low pH of the plantsap (i.e. pH 2) possibly plays a negative
role in these experiments. However, the virus could be transmitted mechanically
to virus-free B. semperflorens. Molecular characterisation was
more successful. Total RNA from an infected plant was subjected to a RT-
PCR procedure using degenerate potyvirusspecific primers (Van der Vlugt et
al, 1999). A 653 nt. cDNA-fragment covering the C-terminal part of the viral
coat protein (CP) and the 3’non-translated region (3’NTR) was obtained and
cloned. The sequence was compared with other viral sequences present in the
NCBI database. The CP and 3’NTR nucleotide sequences showed a maximum
of 73% and 46% homology with potyvirus sequences present in the
database. This suggests that the begonia potyvirus represents a hitherto unidentified
potyvirus. For this new potyvirus found in B. semperflorens the
name Begonia flower break virus is proposed.
High frequency silencing of multiple targets using a single inverted repeat
construct
E Bucher, RW Goldbach and MW Prins; Laboratory of Virology, Wageningen University
The use of RNA silencing has become the tool of choice for gene knockdowns
in plants and many other organisms. The discovery that doublestranded
RNA (dsRNA) is a very good trigger for RNA silencing is the key
element in this technology. By arranging transgenes as inverted repeats (IRs),
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