Heat requirements for red grapevine cultivars in the wine-producing region of Sremski Karlovci, Serbia

Heat requirements for four major phenological stages (budburst, flowering, veraison and harvest) were assessed in eight red grapevine cultivars grown in the Sremski Karlovci region in northern Serbia using a growing degree-days (GDD) method and base temperature of 10 degrees C. Temperature and phenological data covering the period 1986-2007 were used to conduct the study. The accumulated GDD for the beginning of budburst ranged from 70 ('Gamay' and 'Limberger') to 92 ('Cabernet Sauvignon'). The heat requirements for the beginning of flowering varied between 338 GDD in 'Gamay' to 398 GDD in 'Probus'. The smallest heat requirements to reach the beginning of veraison was observed in 'Portugizer' (937 GDD) and the greatest in 'Probus' (1117 GDD). The GDD for harvest spanned the range from 1555 in 'Portugizer' to 1649 in 'Prokupac'. Generally, a greater variation in GDD was found between years for a single cultivar than among cultivars within individual years. Among phenological stages, the greatest inter-annul variation in terms of coefficient of variation was displayed for the beginning of budburst and the least for harvest.