Resumen Las relaciones serológicas y la diversidad genética de cepas argentinas de grapevine leafroll associated virus 4 (GLRaV-4) fueron analizadas. El análisis filogenético de la cápside proteica (CP) conducido sobre las secuencias obtenidas mostró un agrupamiento de las primeras con GLRaV-4 raza 5, GLRaV-4 raza 6 y GLRaV-4 raza 9. El análisis evolutivo de las secuencias locales y las disponibles en bases de datos infirió eventos de recombi nación y sugirió que tanto los extremos C-terminal como N-terminal de la CP están bajo presión de selección purificante, pero la región N-terminal mostró siete sitios bajo presión de selección positiva, con una relación d N/d S cinco veces mayor que aquellas posiciones de la región C-terminal. La reactividad serológica contra anticuerpos monoclonales sustenta la probabilidad de ocurrencia de epitopes lineales en la región N-terminal inferida en el análisis evolutivo. Los resultados obtenidos reflejan un comportamiento evolutivo inusual de la CP y junto con la reactividad serológica de dicha proteína, permiten postular una significancia biológica de dicha variabilidad.

Abstract This research studied serological relationships and genetic diversity of Argentinean isolates of grapevine leafroll-associated virus-4 (GLRaV-4). Phylogenetic analysis of coat protein (CP) sequences from 19 local isolates revealed clustering with the previously described GLRaV-4 strain 5, strain 6, and strain 9 groups. Evolutionary sequence analysis of the obtained and database-available sequences showed evidence of recombination events. Additionally, both CP N- and C-terminal regions appeared to be under purifying selection, but the N-terminal region presented seven sites under positive selection, with a d N/d S ratio 5-fold greater than that of the C-terminal region. Serological reactivity against monoclonal antibodies supports a higher occurrence probability for linear epitopes in the N-terminal region, as inferred by the sequence analysis. The obtained results reflect an unusual evolutionary behavior of the CP that, together with protein serological reactivity, suggests biological significance of the observed variability.

A viticultura é importante para a economia da Argentina, especialmente na província de Mendoza, que abrange mais de 75% da área cultivada do país. Neste trabalho, nós avaliamos a incidência de Grapevine leafroll associated virus (GLRaV) -1, -2 e -3 em clones de Vitis vinifera das cultivares Cabernet Sauvignon, Cabernet Franc e Sauvignon Blanc, cultivadas em diferentes zonas de Mendoza. Os clones selecionados foram previamente relatados como provavelmente infectados por GLRaV-2. Todas as amostras selecionadas foram analisadas por DAS-ELISA para GLRaV-1, -2 e -3. GLRaV-2 foi o único vírus identificado em todos os clones analisados. As incidëncias das infecçoes globais foram 0,6%, 18,8% e 1,2% para GLRaV-1, 2 e 3, respectivamente. No Cabernet Sauvignon clone 337 a incidëncia da infecção foi muito elevado (68,3%).

Viticulture is important in Argentina's economy, especially in the province of Mendoza, which is responsible for more than 75% of the crop cultivated area. In this work, we evaluated the incidence of Grapevine leafroll-associated viruses (GLRaV) -1, -2, and -3 in Vitis vinifera clones of cultivars Cabernet Sauvignon, Cabernet Franc, and Sauvignon Blanc, planted in different zones of Mendoza. The selected clones were previously reported as putatively infected by GLRaV-2. All selected samples were analyzed by DAS-ELISA for GLRaV-1,-2 and -3. GLRaV-2 was the only virus identified in all the analyzed clones. The overall infection rates were 0.6%, 18.8% and 1.2 % for GLRaV-1, 2 and 3 respectively. For the clone Cabernet Sauvignon 337, the infection rate was very high (68.3%).