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Date: July 2010
Source: Plant Disease [edited]
<http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-94-7-0920A>
[ref: M Budziszewska, et al. First report of _Potato mop-top virus_ on potato in Poland. Plant Dis 2010; 94, 920; DOI: 10.1094/PDIS-94-7-0920A]
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_Potato mop-top virus_ (PMTV) is a serious pathogen occurring in Northern Europe, North and South America, and Asia that significantly reduces potato (_Solanum tuberosum_) production. PMTV is transmitted by _Spongospora subterranea_, the causal agent of potato powdery scab, and causes characteristic brown arcs and circles (spraing symptoms) in potato tubers, stunting of stems, shortening of internodes, and mosaic patterns (V-shaped) on leaves, as well as leaf necrosis. _S. subterranea_ and PMTV are mainly associated with cool, humid environments.
Between 2005 and 2009, extensive surveys for PMTV were conducted in Polish potato fields with an emphasis on areas neighboring countries where the virus had previously been reported. About 18 000 tubers from 39 cultivars from different regions of Poland were collected. Tubers were first visually inspected for symptoms within the flesh and then selected tubers were analyzed by double-antibody sandwich (DAS)-ELISA. Symptomatic samples tested by ELISA gave signals about 3-fold higher than negative controls and about 2- to 5-fold lower than PMTV-positive controls.
RT-PCR on tubers testing positive for PMTV by DAS-ELISA amplified a 530-bp product. No PMTV was detected in Poland between 2005 and 2007. In 2008, one tuber (cv. Inwestor) from central Poland tested positive for PMTV and the sequence and was submitted to GenBank. In 2009, additional infected tubers were found in 3 Polish cultivars (Bartek, Glada, Ruta) from the same county. Sequence comparisons revealed 99 per cent nucleotide identity and approximately 98 per cent amino acid identity to Czech, Swedish, and Finnish PMTV isolates.
To our knowledge, this is the 1st report of PMTV in Poland. Poland is one of the major potato-producers in Europe with the 2008 crop around 10 million tonnes. If PMTV spreads in Poland, the virus could threaten potato production.
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[Potato mop-top virus (PMTV; genus _Pomovirus_, unassigned to a family) spreads in Eurasia, South, and Central America. Other than potato, some weed species of _Chenopodiaceae_ and _Solanaceae_ are commonly infected in the Andean region but not elsewhere. Tuber yield may or may not be reduced, but economic losses are due to quality being severely affected.
Tuber symptoms called "spraing" include brown lines, rings, and flecks.
They normally remain internal but occasionally may extend to the surface, and some PMTV affected tubers may not show any symptoms. Spraing increases in cool temperatures and with storage. Leaf and stem symptoms only appear if infected tubers are planted. They depend on variety and environmental conditions but may include yellow leaf blotches, leaf distortion, and shortened internodes (mop-top).
PMTV is spread by the potato powdery scab pathogen _Spongospora subterranea_ (recently reclassified from fungus to protozoan) where it is retained in the sponge-like spore balls. The virus can survive in the vector for up to 18 years in the soil. Viruliferous vector can be spread with soil by human activities. PMTV transmission through tubers is variable and not all stems produced by a PMTV-infected tuber may become infected. In the absence of the vector it is thought that plants may become free of the virus after 3 generations.
Disease management is difficult and generally directed at the vector. It may include phytosanitation to minimise soil being carried on tubers or equipment, cultural techniques, chemical treatments of seed tubers, soil treatments to reduce spore numbers of the vector, and crop rotation (particularly with _Brassica_ species).
Maps
Poland:
<http://graphicmaps.com/webimage/countrys/europe/lgcolor/plcolor.htm>
Provinces of Poland:
<http://www.lib.utexas.edu/maps/europe/poland_pol00.jpg>
Pictures
Potato tubers with spraing:
<http://www.umext.maine.edu/images/spraing1.jpg> and <http://www.mm.helsinki.fi/mmsbl/english/research/Kpat/ryhmat/moptop/
moptop1_2.JPG>
PMTV leaf symptoms:
<http://www.gov.mb.ca/agriculture/crops/potatoes/images/bda04s07-p29.jpg> and <http://www.inspection.gc.ca/english/plaveg/pestrava/pmtv/images/pmtv1.jpg>
Powdery scab on potato tuber:
<http://www.spongospora.ethz.ch/potato1.jpg>
Links
Information on PMTV:
<http://www.umaine.edu/umext/potatoprogram/Fact%20Sheets/PMTV%20fact%20sheet.pdf>,
<http://www.umext.maine.edu/onlinepubs/htmpubs/2437.htm>, and <http://www.inspection.gc.ca/english/plaveg/pestrava/pmtv/tech/pmtve.shtml>
_Potato mop top virus_ taxonomy and description:
<http://www.ictvdb.rothamsted.ac.uk/ICTVdB//00.086.0.01.001.htm>
Information on potato powdery scab and _S. subterranea_:
<http://www.spongospora.ethz.ch/sss.htm>,
<http://www.umext.maine.edu/onlinepubs/htmpubs/2436.htm>, and <http://www.uiweb.uidaho.edu/ag/plantdisease/scabnote.htm>
_S. subterranea_ life cycle:
<http://www.spongospora.ethz.ch/slides.htm>
_Spongospora subterranea_ taxonomy:
<http://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=121480>
Taxonomy and reclassification of genus _Spongospora_:
<http://www.spongospora.ethz.ch/intro.htm>. - Mod.DHA]
[see also:
2003
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Potato mop-top virus, potato - USA (Maine) 20030707.1660 Potato mop-top virus, potato - Canada (Nova Scotia) 20030105.0038
2002
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Spongospora spp., potato - Costa Rica 20021023.5623 Potato mop-top virus, potato - Canada (P.E.I) 20021010.5510 Potato mop-top virus, potato - North America 20020928.5422 Potato mop-top virus, potato - USA (FL, ID & MD) 20020821.5106 Potato mop-top virus, potato, first report - USA (Maine) 20020810.5017]
Species
