Training systems evaluation of Vitis vinifera L. 'Alvarinho' (Vinhos Verdes PDO region) to physiological and productive parameters

In the Vinhos Verdes wine region, the largest Protected Designation of Origin (PDO) region in Portugal, the most common 'Alvarinho' training system is single downward shoot positioning (DSP), which is currently being replaced by vertical shoot positioning (VSP). This work aimed to evaluate physiological and productive parameters of 'Alvarinho' grapevines in both training systems. This study was carried out in 2018 in a commercial vineyard in Monção (north-west of Portugal). It was divided into two plots, of 1 ha and 0.5 ha respectively, and each with a different training system. On each plot, 4 replicates were established with 7 vines replicate^-1. Soil texture on both plots is sandy loam from schist, and soil water capacity is 290 mm m^‑1. The vineyards were planted in 2009, with 196-17 rootstock, and with a density of 1111 vines ha^-1, in north-south oriented rows. From July to August, nine irrigation events were performed applying a total of 95 mm of water on each plot. From blooming until harvesting, in 2 vines replicate^‑1, the soil water content, the crop water stress index (CWSI) and the index of relative stomatal conductance (I_G) were recorded along with the stem water potential, chlorophyll content and photosynthetically active radiation. The production and vegetative parameters (bunch number, weight per bunch, pruning wood weight and Ravaz index) were calculated on 7 vines replicate^‑1. From veraison until harvesting the DSP system showed higher stem water potential than VSP, yet no differences in stress indicators (CWSI and I_G) were found between training systems. The main differences were in yield parameters where the DSP showed more bunches per vine (95 vs. 81), higher production per vine (13 vs. 9.1 kg vine^‑1), and higher Ravaz index (6.2 vs. 2.5).