Alfalfa dwarf disease, a viral complex affecting alfalfa crop in Argentina

TRUCCO, VERÓNICA; BEJERMAN NICOLAS; DE BREUIL SOLEDAD; CABRERA-MEDEROS, DARIEL; LENARDON, SERGIO LUIS; GIOLITTI, FABIÁN JOSÉ

Cordoba

Congreso; Second World Alfalfa Congress; 2018

Alfalfa (Medicago sativa L.) is considered the most important forage crop in Argentina and an essential component of bovine meat and milk production. It is well adapted to a large region in Argentina due to its high salinity and drought resistance as well as its efficient atmospheric nitrogen-fixing capacity (Basigalup et al., 2007). Alfalfa is the forage crop with the largest cultivated area in the country, over 3.2 million hectares, and it ranks fourth after soybean, wheat and maize (Basigalup pers.comm., 2018; «Bolsa de Cereales», 2018; «Bolsa de Comercio de Rosario», 2017). In 2010, a new viral disease, named alfalfa dwarf disease-ADD, was identified in Argentina. The symptoms include severe plant stunting and leaves with decreased size, distortion, chlorosis and the presence of vein enations and papillae on the abaxial surface (Figure 1). Initial field assays indicated that ADD presented incidences higher than 50%, yield decreases of dry mass of up to 30% and significantly reduced crop life (INTA-Informa, 2010). Plants infected with ADD were found to be co-infected with Alfalfa mosaic virus (AMV) and Alfalfa dwarf cytorhabdovirus (ADV). Subsequently, other three viruses were detected in the same plants: Bean leafroll virus (BLRV), Alfalfa enamovirus-1 (AEV-1) and Alfalfa leaf curl virus (ALCV). So far, these five viruses (collectively named as Argentine Alfalfa Viruses = AAV) were detected in alfalfa plants, with ADV and AEV-1 being virus species described for the first time worldwide. Methods for AAV detection were adjusted and the complete genome sequences of each virus were reported (Bejerman et al., 2011, 2015, 2016, 2017; Trucco et al., 2014, 2016). Taking into account that little is known about viral diseases affecting alfalfa and considering the importance of this forage crop for cattle production in Argentina, our objective was to generate data to elucidate the situation of the viral disease complex in this crop and the relative importance of each component of the disease complex; meeting this objective will be an important step toward adopting methods for their proper management.