Evaluación de la virosis del achaparramiento de la alfalfa (Medicago sativa L.) en dos ambientes contrastantes de Argentina

In the last years, it has been observed an increasing damage from a viral disease affecting the production and persistence of alfalfa in Argentina. The objective of this work was to compare the incidence and severity of the disease symptoms and to explore the relationship of its dynamics with respect to rainfall (pp) and temperature (T) in six commercial alfalfa cultivars during the period 2010-2014. The cultivars CW1010, WL1058, Traful PV INTA, WL903, Monarca SP INTA and LPS8500 were evaluated in trials at EEA Manfredi-INTA and at EEA Santiago del Estero-INTA. In both trials, mean incidences between 50% and 80% were recorded, with significant interannual variability and differences among cultivars. The severity was higher for the cultivars evaluated in Santiago del Estero. Cultivars WL903 and WL1058 presented the lowest severity, while LPS8500 and Monarca SP INTA showed the highest values. As for the climatic variables used for this analysis, pp (pp + irrigation in Santiago del Estero) and maximum T were the variables that mostly determined the incidence of the disease. Mean T was the most important variable regarding severity.