Training System and Methyl Jasmonate Application: A Tool to Improve Major Polyphenol Consumed by the Brazilian Population in Grape Juice

In this research,
the effects of foliar methyl jasmonate (MJ) were
evaluated on the phenolic composition of five grape varieties cultivated
using a Pergola and Vertical Shoot Position (VSP). Their grape juice
was investigated using UPLC-QTOF analysis over two seasons. Caffeic
acid derivatives, such as caftaric acid and caffeic acid glucoside,
were the most responsive hydroxycinnamates in the study. MJ significantly
increased the anthocyanin content in the “Isabel” juices
from a high-productivity training system (“Pergola”).
The juice from treated grapes of ‘Isabel Precoce’ variety
yielded promising results, as the total soluble solids content was
higher during the experiment. The VSP system also yielded a positive
reaction after MJ treatment for anthocyanins and hydroxycinnamates
in ‘Ives’ variety. In conclusion, the integrated approach
of varieties and training system enhances the MJ treatment efficacy,
enabling the preparation of blends of grape juice, leading to improvements
on quality and phenolic composition.