Terroir aspects of grape quality in a cool climate wine region: Relationship between water deficit, vegetative growth and berry sugar concentration

Abstract

Gas-exchange, water relations, vegetative growth and berry sugar concentration of the Kékfrankos grapevine were studied at two growing sites in Eger Wine district, Hungary (Eger-Kőlyuktető – non-stressed, flat vineyard and Eger-Nagyeged hill – water stressed, steep slope vineyard). At the hilly site predawn water potentials and stomatal conductance indicated mild to moderate water stress. As a result, stomatal regulation caused restricted carbon assimilation per unit leaf area. Interestingly, comparing the two sites, lower assimilation rate was accompanied by higher fruit sugar concentration. Water deficit also reduced the yield and the relative proportion of larger berries within bunches. However, in each berry weight category (I: <1 g, II: 1.01–1.25 g, III: 1.26–1.5 g, IV: 1.51–1.75 g, V: 1.76–2 g, VI: >2.01 g) there was a higher sugar concentration at the water stressed vineyard irrespective of berry size. Therefore, berry size was not the only factor that could influence berry sugar concentration. Water deficit also resulted in decreased leaf area per shoot and thus, modification in canopy architecture. Although, there was a higher leaf area for 1 kg fruit at the flat vineyard compared to the hilly site, differences in “sink-source” relations and light interception of the canopy between the sites resulted in different yield sugar concentration.