PHYTO MEDIZIN Mitteilungen der Deutschen ... - Die DPG

crop species. Rye became earlier infected than wheat and triticale if sown at
the same time. Visual inspection of the field revealed that rye plants showed
clear symptoms already early in February whereas wheat and triticale plants
developed symptoms later in March. Both furoviruses tolerate a broad temperature
spectrum under field conditions and once established infection by
these viruses is detectable until the harvest time. In contract to this, the
propagation of the bymovirus WSSMV seems to be restricted to lower temperatures.
Consequently, this virus is detected best at the end of February
until beginning of April. A survey in the cereal growing regions of Saxony-
Anhalt and Lower Saxony revealed that there only SBCMV and WSSMV are
spread. There rye cultivars appear to be more heavily infected than different
cultivars of wheat and triticale.
Dutch-German cooperations in evaluating species demarcation criteria
for tombus- and tymoviruses
R Koenig 1 , JThJ Verhoeven 2 , CWA Pleij 3 and D-E Lesemann 1; 1 Biologische Bundesanstalt,
Institut für Pflanzenvirologie, Mikrobiologie und biologische Sicherheit,
Braunschweig, 2 Plant Protection Service, Wageningen and 3 Leiden Institute of Chemistry,
Leiden University
The VIIIth Report of the International Committee on Taxonomy of Viruses
(ICTV) lists biological, serological and molecular properties as species demarcation
criteria for tombus- and tymoviruses as well as for many other
plant virus genera. In attempts to characterise and classify newly detected
tombus- and tymoviruses we have compared the usefulness of the various
species demarcation criteria for these viruses. Five new tombusvirus isolates
all from the same natural host, i.e. commercially grown statice (Limonium
sinuatum) from various parts of the world, were more or less indistinguishable
in limited host range studies, but by means of immunoelectron microscopy
they were readily distinguished and four of them could be assigned to
various known tombusviruses. Coat protein sequence comparisons indicated
that none of them was exactly identical to one of the previously described
viruses. - In the genus tymovirus total nucleotide and coat protein amino acid
sequence identities revealed similar groupings as earlier serological studies.
The latter, however, tended to suggest much closer relationships than the
molecular data and may fail to recognise a new tymovirus as being distinct.
Thus, a new tymovirus (provisionally named Nemesia ring necrosis virus)
which is widely spread in commercially grown genera in the Scrophulariaceae
and Verbenaceae was serologically barely distinguishable from the
earlier described Scrophularia mottle virus. Molecular studies, however,
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