High throughput LC-MS phenolic composition analysis of fungus-resistant grape varieties cultivated in Italy and Germany

The fungus resistant grape varieties PIWI (from the German word “pilzwiderstandsfähig”) were created by crossing European and American varieties, with the aim to combine the good resistance to diseases and phylloxera of the American grape varieties with the high quality of European varieties. Although are already cultivated in Europe for decades and there is an increase interest from the part of the producers and consumers, the information about their phenolic profile is very limited even though phenolics have a key role in the resistance mechanism. Aim of this work was to analyse the phenolic composition of grape berries from Cabernet Cortis, Johanniter, Solaris, Regent and Phoenix cultivars grown in Italy and Regent and Phoenix cultivars grown in Germany by two supplementary LC-MS/MS methods. To study the analytical methods robustness, tools commonly used in untargeted metabolomics methods were chosen and applied. For example, biological, technical and instrumental replications were included in order to study the variability at different levels. In total, 55 phenolics were quantified, belonging to various classes of the polyphenols biosynthetic pathway. The knowledge of the PIWI polyphenolic profile could be helpful for better understanding their resistance mechanism and future cross-breeding. Moreover, was found the above PIWI varieties to have a rich phenolic profile compared to Vitis vinifera cultivars, especially in the class of stilbenes. Finally, according to the results, biological variability was of great importance and included technical replicates at the same time, while injections of a QC pooled sample throughout sample analysis provided important information about instrumental accuracy and sensitivity.