Minimal pruning as a tool to increase the anthocyanin: sugars ratio in grapes

Abstract

Minimal pruning (MP) is considered as a possible alternative technology in vineyards in the face of global warming. In order to evaluate its effect on grapes cultivated in warm areas, a long-term study about minimal pruning on Tempranillo (Vitis vinifera L.) was conducted in Badarán (La Rioja, Spain). For every vintage between 1999 and 2013, grapes from minimal-pruned vines and the vines of control treatment were harvested at the same time; Yield and total soluble solids (TSS, oBrix) were determined. On this basis, a further study was initiated in 2014, aimed at comparing berry qualities between the two treatments and at verifying the positive effects of MP on wine industry under global warming. The above mentioned long-term study showed that MP, on average, increased yield (+100%) and reduced the TSS content (-8%) compared with the control treatment. The 2014 study demonstrated that berries from the MP group got a similar level of TSS content as that of the control group 20 days later. At the same level of TSS content, compared with the control group, must from MP group, significantly, had smaller berry size (-35%), smaller cluster size (-60%), larger yield (+77%), smaller leaf-fruit ratio (-32%), more total acids (+37%), higher PH (+6%), more tartaric acid (+13%), less malic acid (-15%). And above all, must of MP group presented higher anthocyanin content (+17%) as well as higher anthocyanin : sugar ratio (+21%). The current results show that MP can effectively delay berry ripening and restore the anthocyanin : sugar ratio, or/and reduce wine alcohol content; The results also support the hypothesis that MP does help to improve berry quality in warm climatic conditions.