Detection of Potato Mop-Top Virus in potato tissues and soil
Graham Cowan and Lesley TorrancePotato mop-top virus (PMTV) is soil-borne and has tubular rod-shaped particles. It is
found in potato growing areas in Europe, Canada, South America and Asia that have
a cool wet climate. It wasrecently identified in the USA (2002) and an extensive
survey revealed that it was widespread in potato producing states.
The symptoms induced by PMTV vary greatly with potato cultivar. Typical tubersymptoms of brown lines, arcs or rings (spraing) in tuber flesh and raised external
lines appear in the year of infection when the virus is transmitted to potato by the
soil-borne ‘fungus’ Spongosporasubterranea f. sp. subterranea, the causal agent of
powdery scab disease. Plants grown from infected tubers show yellow markings
and chevrons in the leaves some cultivars display shortening ofinternodes (moptop).
Substantial yield losses (ca. 20 percent) have been reported in sensitive
cultivars due to decreased tuber production and quality. Symptoms of PMTV can be
confused with thoseinduced by Tobacco rattle virus (a nematode transmitted virus)
and reliable diagnosis is needed since control measures differ.
Virus-carrying Spongospora resting spores can remain viable in soil for manyyears
and potatoes were infected with PMTV when planted in a field 18 years after
potatoes were last grown. There is no effective, environmentally safe chemical
control of S. subterranea and thebest method to prevent spread of PMTV is to plant
virus-free tubers on PMTV-free land.
Several sensitive methods to detect and identify PMTV have been devised at SCRI.
The ELISA method is based onantibodies that are specific for
PMTV coat protein. The
advantage of this method is that
sample preparation procedures
are simple and fast enabling many
thousands of tests to be done in a