V. Haygarov1, T. Yoncheva1, Z. Nakov2, M. Ivanov2, D. Dimitrov1* 1Department of Enology and Chemistry, Institute of Viticulture and Enology, 1 Kala Tepe str., 5800 Pleven, Bulgaria 2Department of Cultivars and Cultivar Maintenance, Institute of Viticulture and Enology, 1 Kala Tepe str