Incidence of grape anthracnose on different VITIS labrusca and hibrid cultivars and rootstocks combination under humid subtropical climate

Anthracnose is a severe disease present in several grape production areas; it is considered a tropical disease. In South Brazil, high relative humidity and other conditions favor the occurrence of fungal disease in vineyards. The objective of this study was to evaluate the anthracnose incidence progress in grape leaves in three scion cultivars (Concord, Bordô and BRS Carmem) in combination with three rootstock (1103 Paulsen, VR 043–43 and IAC 766), in regional climatic conditions favorable for disease development. The experiments were carried out on ridges with semi-trellis system. The experimental design was randomized blocks, with split plots, with 4 replications and 4 plants per plot. The plots were represented by 9 different combinations. Disease incidence was assessed at two week-interval from September to March (2010/2011, 2011/2012, and 2012/2013). At each sampling, disease was assessed 10 leaves of a same shoot of 6 plants for each cultivar/rootstock combination, for a total of 54 plants. All cultivar-rootstock combinations showed disease symptoms with highest disease incidence coinciding with the greatest amount of precipitation. Based on the relative area under the disease progress curve (AUDPC), the anthracnose incidence showed differences between seasons. Differences between rootstocks and rootstock/cultivar combinations were observed during the first and third season, but there was no consistency between the seasons, indicating that the variation in disease progress could be due to other factors, including as weather conditions, age of the vineyard and inoculum pressure.