Outbreak of Mal de Río Cuarto in Argentina
‘Mal de Río Cuarto’ is the most important virus disease of maize in Argentina. It was first detected in the department Río Cuarto, in the Province of Cordoba. The disease is currently spreading to most maize-growing areas of Argentina. It is also reported to be present in maize-growing regions in the south of Brazil and Uruguay. A recent outbreak took place in Argentina and it was estimated that in 1996-1997, approximately 300,000 ha of maize were affected and yield losses reached 120 million USD. ‘Mal de Río Cuarto’ is caused by a fijivirus, whicht was initially thought to be a geographic strain of the maize rough dwarf fijivirus (which occurs also in the Mediterranean region), as symptoms are similar. But molecular hybridization tests indicated that they are most probably distinct viruses. ‘Mal de Río Cuarto’ is transmitted by the insect Delphacodes kuscheli (Homoptera: Delphacidae) in a persistent way, but is apparently not transmitted by seeds. The virus has been detected in many weeds of the families Poaceae and Cyperaceae (e.g. Arundo donax, Cenchrus echinatus, Cyperus cayennensis, Cyperus rotundus, Cynodon dactylon, Digitaria sanguinalis, Echinochloa colonum, Eleusine indica, Eragrostis virescens, Setaria geniculata, Setaria verticillata, Sorghum halepense), in sorghum (Sorghum bicolor), millet (Panicum miliaceum), foxtail millet (Setaria italica) and oat (Avena sativa). Recently, it has been shown that wheat could be affected by the virus (up to 24 % disease incidence observed in the endemic disease area), and that it could play a double role in the epidemiology of the disease, as a virus reservoir and as a preferred host for the development of the vector D. kuscheli.
Sources
Lenardon, S.L.; March, G.J.; Nome, S.F.; Ornaghi, J.A. (1998) Recent outbreak of ‘Mal de Rio Cuarto’ virus on corn in Argentina.
Plant Disease, 82(4), p 448.
Rodriguez Pardina, P.E.; Giménez Pecci, M.P.; Laguna, I.G.; Truol, G. (1998) Wheat: a new natural host for the Mal de Río Cuarto virus in the endemic disease area, Río Cuarto, Córdoba Province, Argentina.
Plant Disease, 82(2), 149-152.
Further reading on INTERNET
http://www.hq.satlink.com/IPP/iffive/jica/english/mai.htm
http://www.unc.edu.ar/temp
http://www.inta.gov.ar/proynac/80001.html