September 20, 2004
From: ProMED-mail<promed@promedmail.org>
Source: Australasian Plant Pathology Journal [edited]

First report of wheat streak mosaic virus infecting wheat in Argentina
G Truol, M Sagadin, Instituto de Fitopatologia y Fisiologia Vegetal (IFFIVE)-INTA, Cordoba, Argentina; R French, USDA-ARS, University of Nebraska, Lincoln, USA; J Arneodo, Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONCICET), Argentina. Corresponding author: <glaguna@correo.inta.gov/ar>

Wheat streak mosaic virus [WSMV] has been detected for the first time in Argentina in wheat crops (_Triticum aestivum_) growing in the central area of the country (Cordoba province). Virus identity was established by host
range experiments, electron microscopy, serology, and polymerase chain reaction (PCR).

[Unless I am mistaken, this report may be the 1st report of WSMV in South America. The virus is a member of the genus _Tritimovirus_, family _Potyviridae_, and is transmitted by the eriophyid mite _Acer tosichella_. Characteristic WSMV particles (700 x 15 nm) were observed in electron micrographs from infected wheat and confirmed by serological tests.

Damage to wheat crops can range from complete crop failure to severe reduction in yield. The outbreak in Argentina was observed in cvs. ACA 223, Baguette and Buck Guapo in wheat fields in Cordoba province. WSMV has been reported from Canada, China, Czech Republic, Hungary, Iran, Jordan, Mexico, Poland, Rumania, Russia, Turkey, Ukraine, USA, the former Yugoslavia and Syria.

In North America, conditions favoring spread of the disease are the presence of a source of infection coupled with early planting of winter wheat. Severe losses can occur in early planted fields of winter wheat and spring wheat. _A. tosichella_ needs living plants to survive year-round. Nymphal mites can acquire the virus after feeding for 15 minutes or more on infected plants, and they remain viruliferous for several days in the absence of infected plants.
 
High sequence identity of US and Turkish WSMV genotypes suggests that humans assisted the movement of WSMV across the Atlantic. Immigrants from the Crimea initiated the hard red winter culture in South Dakota, Nebraska, and Kansas in the 1880s, and germplasm exchange was frequent between the Great Plains of North America and the Black Sea. WSMV is reportedly seedborne at low rates (0.1-0.2 per cent) in maize and wheat, and both the virus and its vector could have been transported across the Atlantic in grain shipments.

Disease management depends upon eliminating or destroying volunteer wheat and susceptible weeds before the new crop is sown.

References: <http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex107?opendocument> 
<http://vir.sgmjournals.org/cgi/content/full/83/4/895>

I have only included the 1st and 12th postings to save space. - Mod.DH]