Published Date: 2012-11-01 20:48:35
Subject: PRO/PL> Phytoplasmas, potato - Romania, Russia (Southern): surveys
Archive Number: 20121101.1385861
PHYTOPLASMAS, POTATO - ROMANIA, RUSSIA (SOUTHERN): SURVEYS
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: September 2012
Source: European Plant Protection Organisation (EPPO) Reporting Service 9/2012/187 [edited]
Surveys were carried out in 2008/2009 to identify phytoplasmas associated with potato crops in Romania and southern Russia using molecular techniques. Symptomatic potato plants (_Solanum tuberosum_) were collected from several fields in both countries and tested by PCR for the presence of phytoplasmas. Samples of weeds (e.g. _Convolvulus arvensis_) and adjacent crops (including _Beta vulgaris_, _Capsicum annuum_, _Solanum lycopersicum_, _S. melongena_, _Zea mays_) were also included.
In both countries, stolbur was the only phytoplasma detected in potatoes. It is noted that a large number of potato tubers (27 percent) collected from phytoplasma-infected fields had a spongy appearance which resulted in commercially unacceptable potato chips upon processing. Genotyping of obtained stolbur isolates revealed that they all had the same genotype known to be associated with the weed _C. arvensis_. These results suggest that this weed probably constitutes a major source of inoculum for potato crops in Romania and southern Russia.
The results of these surveys indicate that stolbur is a major pathogen associated with phytoplasma diseases of potato in Romania and southern Russia. Stolbur was also detected in tomato, beet, capsicum, aubergine [eggplant] and weed samples.
[Ref: I Ember et al. Survey and molecular detection of phytoplasmas associated with potato in Romania and Southern Russia. European Journal of Plant Pathology (2011) 130, 367-377.]
[_Candidatus_ Phytoplasma solani (potato stolbur phytoplasma) is the type member of the stolbur (16SrXII) phytoplasma taxonomic group and has been included in the EPPO A2 quarantine list. It has a wide host range and is known to affect around 45 species of _Solanaceae_ (including crops such as potato, tomato, capsicum and aubergine), as well as further species in 6 other families.
In potato, symptoms may include discolouration and distortion of leaves, progressive wilting, leaf necrosis and spongy tubers. Sprouts may be hair-like, weak, and stunted but can return to normal later. The disease may cause heavy yield losses of up to 80 percent and can result in the total destruction of whole potato fields. Remaining tubers are mostly unmarketable.
Phytoplasmas are intracellular pathogens and can be spread with infected plant material (tissue cultures, grafting) and planthopper vectors. For stolbur, _Hyalesthes obsoletus_ is considered the most important vector in parts of Europe. Transmission with potato tubers has also been shown, at least in some varieties. Disease outbreaks seem to occur in cycles, being favoured by hot dry summers, which stimulate vector migration into crops. The crop hosts are normally not important for the continuity of the pathogen, which prefers several species of wild plants which act as pathogen reservoirs (such as, according to the report above, _C. arvensis_). Disease management for phytoplasmas may include vector control, removal of pathogen and/or vector reservoirs (volunteer crop plants, weeds), use of clean planting material, and resistant varieties.
Other species of the stolbur group have been reported from Europe and parts of Asia and Africa causing diseases in a range of dicotyledonous crops (for example, bois noir, a serious disease of grapevine) and a few monocot hosts (including maize and sugarcane).
Other phytoplasma diseases of potato include purple top (aster yellows phytoplasma), witches' broom, marginal flavescence, purple toproll and phyllody. Similar disease symptoms can be caused by different pathogens in different areas, and further work is needed on taxonomy and relatedness of some of the potato phytoplasmas.
Russian regions via:
Europe, overview: http://www.edinphoto.org.uk/0_MAPS/0_map_europe_political_2001_enlarged.jpg
_Ca._ P. solani symptoms on potato: http://www.forestryimages.org/images/768x512/0454069.jpg and http://www.forestryimages.org/images/768x512/0725024.jpg
Stolbur symptoms on tomato:
http://www.forestryimages.org/images/768x512/0176080.jpg and http://www.apsnet.org/mpmi/covers/2006/mja06cvr.htm
_H. obsoletus_ vector:
_Convolvulus arvensis_, field bindweed:
Information on potato stolbur phytoplasma disease:
_H. obsoletus_ information:
_Ca._ Phytoplasma solani taxonomy:
Stolbur phytoplasma group taxonomy and species list: http://www.uniprot.org/taxonomy/85632
_Ca._ Phytoplasma taxonomy and species groups:
Phytoplasma diseases of potato:
Phytoplasma resource centre, information, and pictures: http://plantpathology.ba.ars.usda.gov/phytoplasma.html
EPPO A2 quarantine list:
Information on _C. arvensis_ via:
A HealthMap/ProMED-mail map can be accessed at: http://healthmap.org/r/1z-D.]