COMPARISON OF GRAPE SEEDLINGS POPULATION AGAINST DOWNY MILDEW BY USING DIFFERENT PROVOCATION METHODS

Abstract

This research was conducted to compare a laboratory technique leaf disk with hotbed and field evaluations in the screening of large populations of grape seedlings (Vitis spp.), towards downy mildew (Plasmopara viticola Berk. et Curt.) resistance. Seedlings produced by crossing two hybrid families, in (Vitis amurensis Rupr. x Vitis vinifera L.) x (Franco-American hybrid x Vitis vinifera L.) and the antipodal crossing of the Franco-American hybrid x Vitis vinifera L. x (Franco-American hybrid x Vitis vinifera BC) combinations. The 'Bianca', 'Merzling', 'Kunleany', 'Hibernal' and 'Hibia' cultivars were used. These varieties were rated for sporulation on five levels, from 0 to 80 percent. Sporulation ratings were assessed at the first and second rating. Significant differences were signalled between field evaluations and the leaf disk technique. Furthermore, a highly significant correlation was found between the leaf disk technique and hotbed evaluation. The leaf disk procedure appeared to be a good predictor of field resistance and is more practical than the hotbed provocation method for the screening of large populations.