Arch Virol (2003) 148: 381–388
Identiﬁcation of two nucleotide sequence sub-groups
within Potato mop-top virus
S. L. Nielsen and M. Nicolaisen
Department of Plant Protection, Danish Institute of Agricultural Sciences (DIAS),
Research Centre Flakkebjerg, Slagelse, Denmark
Received May 27, 2002; accepted September 17, 2002
Published online November 29, 2002
Summary. To evaluate the variation of Potato mop-top pomovirus from potato
ﬁelds, 21 isolates were collected from different Danish locations. Reverse tran-
scription-polymerase chain reaction-restriction fragment length polymorphism
(RT-PCR-RFLP) of regions of RNA2 was performed for all 21 isolates resulting
in the establishment of two sub-groups of isolates. The nucleotide sequence of a
region encoding part of the ‘readthrough protein’ of RNA2 was compared for 9
of these isolates. This sequence analysis conﬁrmed the RT-PCR-RFLP grouping.
The isolates were tested for symptom expression in indicator plants and grouped
according to symptom development. No correlation between grouping based on
symptom development and genotype was observed.
Rust coloured rings, arcs and ﬂecks in potato tubers known as spraing, are caused
by infection with Potato mop-top virus (PMTV) or Tobacco rattle virus (TRV).
PMTV, the type member of the genus Pomovirus, has tubular particles encapsi-
dating three RNA molecules. RNA1 (6.1 kb.) encodes the viral RNA-dependent
RNA polymerase, RNA2 (3.1 kb.) encodes the coat protein (CP) and a readthrough
protein presumably involved in vector transmission, and RNA3 (3.0 kb.) encodes
the triple gene block and a predicted protein of unknown function . PMTV
is transmitted by Spongospora subterranea f. sp. subterranea [1, 5]. The virus
can survive in the soil for several years inside resting spores of S. subterranea
Nucleotide sequence data reported are available in the GenBank database under the
accession numbers: AF508250–AF508257.