Evaluation of resistance to grapevine powdery mildew (Uncinula necator [Schw.] Burr., anamorph Oidium tuckeri Berk.) in accessions of Vitis species

Abstract

119 accessions, including species from America and Asia, various hybrids and breeding stocks, were tested for resistance to powdery mildew (Uncinula necator) by a leaf disc test. Vitis candicans, V. munsoniana, V. piasezkii and V. rotundifolia were found to be resistant with a rating of up to 1.4 in all accessions (1-no infection, 9-very strong infection). V. munsoniana and V. rotundifolia showed extremely high resistance and may be excellent material for breeding programs. However, the accessions of V. candicans and V. pinsezkii should be preferred for breeding of powdery mildew resistant grapevine Varieties because of the corresponding chromosome number. The surprisingly high number of 10 species included resistant as well as susceptible accessions. V. doaniana and V. tiliaefolia, probably V. palmata and most of the accessions of V. shuttleworthii may be characterized as moderately resistant. V. cordifolia, V. lanata, V. rupestris and some accessions of V. vulpina and cultivars of V. vinifera proved to be highly susceptible.