Phenology and thermal requirements of disease-resistant genotypes (PIWI) grown in the Goethe Grape Valley region of Brazil

Abstract

The Goethe Grape Valley (GGV) is a traditional southern Brazilian region for grape and wine production, mainly planted with hybrid vines. High temperatures and rainfall conditions hamper the cultivation of Vitis vinifera cultivars susceptible to disease, especially Plasmopara viticola. New PIWI (from the German word ‘Pilzwiderstandsfahige’) genotypes of V. vinifera with resistance to P. viticola are under evaluation in this region. The aim of this work was to characterize the phenology and thermal requirements of PIWI genotypes grown in the GGV. The experiment was carried out in an experimental vineyard (28°32’S 49°19’W, altitude 60 m a.s.l.), established in 2016, and evaluations were done for the 2018 vintage. The evaluated PIWI cultivars were ‘Aromera’, ‘Baron’, ‘Calardis blanc’ and ‘Felicia’. Minimum and maximum air temperatures were recorded daily, using 10°C as the low temperature threshold, 25°C as the optimum temperature for development, and 35°C as the upper temperature threshold of development. The evaluated phenological stages were budbreak to flowering, flowering to veraison and veraison to maturity. The total thermal requirement mean was 1360°C day; ‘Felicia’ showed the lowest thermal requirement (1260°C day), which contrasted with ‘Aromera’, which presented the highest thermal requirement (1454°C day). ‘Baron’ and ‘Calardis blanc’ needed 1337 and 1391°C day, respectively, to reach maturity. From budbreak to flowering, the average thermal requirement was 229°C day, from flowering to veraison the mean was 679°C day, and from veraison to maturity the mean was 452°C day. The four evaluated cultivars exhibited adaptive development in the field with thermal requirements compatible with the region of GGV. The results also revealed the lower thermal requirement, and consequently shorter cycle, for ‘Felicia’, as well as the greater thermal requirement of ‘Aromera’.