Variability of Constitutive Stilbenoid Levels and Profiles in Grape Canes (Vitis spp.) depending on Genetic and Environmental Factors

Grape cane is a viticultural by-product that is currently underused or not used at all. Therefore, it bears a high potential for valorization due to the presence of anti-microbially active stilbenoids, being biologically relevant for plant defense. These compounds are highly interesting for applications in the agricultural sector as well as for the food and feed industry.
In this study, we comprehensively investigated the variability of levels and profiles of constitutive stilbenoids in grape canes. First, an HPLC-DAD-MS/MS-based screening of grape canes from 102 different V. vinifera L. cultivars (including seven fungus-resistant varieties) revealed not only a large inter-varietal variability of both total stilbenoid amounts (557-7748 mg/kg DW), but also of their qualitative compositions, showing highly heterogeneous profiles with different predominant stilbenoids (e.g. piceatannol, resveratrol, ε-viniferin or vitisin B). Focusing on each 13 genetically distinct clones of two varieties (Vitis vinifera L. cvs. Riesling and Pinot Noir), a pronounced intra-varietal variability was also observed (e.g., cv. Riesling 3236-6541 mg/kg). 
We furthermore focus on the variability of stilbenoid levels in canes throughout three consecutive vintages (2017-2019) and for three pruning dates (October, December or February) from two cultivars (Pinot Noir and Accent). While varietal differences remained widely conserved throughout the years, strong qualitative discrepancies in stilbenoid profiles between and within seasons became evident. For instance, high contents of oligomeric stilbenoids were found in 2017 and 2019 with decreased temperature and increased precipitation levels, being low in the comparably warmer and dryer year 2018. Furthermore, we clearly show that the pruning date altered the stilbenoid content in grape canes and pruning in December yielded highest levels compared to the two other dates.
In brief, our study provides new insights into the strong variability in grape cane constitutive
stilbenoid levels and profiles in both conventional and fungus-resistant Vitis varieties that are attributed to genetic as well as environmental factors.

Authors: Besrukow Paul1, Irmler Jan1, Schmid Joachim2, Stoll Manfred3, Winterhalter Peter4, Schweiggert Ralf1 and Will Frank1

1Department of Beverage Research, Geisenheim University
2 Department of Grapevine Breeding, Geisenheim University 
3Department of General and Organic Viticulture, Geisenheim University
4Institute of Food Chemistry, Technische Universität Braunschweig

*corresponding author: paul.besrukow@hs-gm.de

Keywords: resveratrol, viniferin, bioactive, phytoalexin, HPLC

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