Resistência ao míldio em genótipos de videira

Abstract

World production of wine is based on the cultivation of European varieties (Vitis vinifera L.), such as Cabernet Sauvignon, Merlot and Chardonnay. Because these varieties have high enological potential. However, the European varieties are sensitive to a range of biotic stresses especially the grape downy mildew (Plasmopara viticola) in southern Brazil. This disease causes high losses and expenses each year due the required applyication of fungicides for its control. The aim of this work was to test the methodology of leaf discs, to assess the level of resistance to downy mildew in two breeding populations: UFP-01 and UFP-02. Leaves of all individuals of the populations were collected and leaf discs of 14 mm were cutted out and placed in petri dishes on moistened filter paper. The disks were inoculated with a spore suspension at a concentration of 50,000 spores.ml-1 and the plates wrapped in BOD at 25°C and a photoperiod of 16h of photoperiod. The evaluation was made using a scale with three resistance levels: 1 resistant plants, without sporulation of the pathogen and presence of necrosis 3 moderately susceptible, presenting reduced sporulation and 5 susceptible, with a high sporulation . For the population UFP-01 two genotypes were scored with (1), five with 3 and sixteen with 5, while in the population UFP-02 four genotypes werescored as 1, twenty-five with 3 and fifteen with 5. Genotypes identified as highly resistant are multiplied vegetatively next growing cycle and deployed to the field to assess the level of resistance under natural infection.