Investigations on the influence of N fertilizer on resistance to powdery mildew (Oidium tuckeri) downy mildew (Plasmopara viticola) and on phytoalexin synthesis in different grapevine varieties

1-year-old grapevine cuttings (cvs. Gf Ga-58-30, Fr 993-60, Riesling, Kerner) were grown in a greenhouse in pots at four levels of nitrogen supply, in order to test their resistance to powdery mildew, downy mildew, and their possible stilbene synthesis. Our most significant findings are that: • increased rates of nitrogen supply decrease the degree of resistance against powdery and downy mildew and phytoalexin (stilbene) synthesis; • the hybrids (Gf Ga-58-30 and Fr 993-60) show a higher powdery and downy mildew resistance and a higher stiloene synthesis than the V. 11inifera varieties (Riesling and Kerner); • the amount of stilbene (resveratrol and E-viniferin) increases during the growing cycle.
VITIS - Journal of Grapevine Research, Vol. 26 No. 4 (1987): VITIS