ACCUMULATION OF GRAPE METABOLITES IS DIFFERENTLY IMPACTED BY WATER DEFICIT AT THE BERRY AND PLANT LEVELS IN NEW FUNGUS DISEASE-TOLERANT GENOTYPES

Abstract

The use of new fungus disease-tolerant varieties is a promising long-term solution to better manage chemical input in viticulture, but unfortunately little is known regarding these new hybrids fruit development and metabolites accumulation in front of abiotic stresses such as water deficit (WD). Thus, prior to the adoption of such varieties by the wine industry in Mediterranean regions, there is a need to consider their suitability to WD.

This study aimed to characterize, from 2019 to 2021, 6 new fungus disease-tolerant varieties selected by INRAE (Floreal, G5 and 3159B for white grapes and Artaban, 3176N and G14 for red grapes) in comparison to V. vinifera Syrah. A gradient of WD was applied and followed by weekly measures of predawn water
potentials. Grape development was non-destructively monitored to determine the arrest of berry phloem unloading, moment at which all grapes were harvested, as way to objectify the sampling date at a precise physiological landmark. Primary metabolites (glucose, fructose, tartrate, malate and yeast assimilable nitrogen) and main cations (K+, Mg2+, Ca2+, Na+, NH₄+) were assessed by HPLC and enzymatic methods. Secondary metabolites as anthocyanins and thiol precursors were assessed by HPLC-UV and LC-MS/MS, respectively.

Genotype was the main factor explaining the variations in metabolites and cation concentration in berries at the ripe stage. At the phloem unloading arrest, primary metabolites and main cation concentra-tions were the lowest in G14 and the highest in Floreal and Syrah. Regarding secondary metabolites, all genotypes showed higher values than the V. vinifera Syrah. Yet, the red hybrid 3176N emerged as the richest genotype in both anthocyanins and total thiol precursors, reaching values of 1609 mg/L and 539 µg/kg respectively. Despite the low contribution of WD to metabolite concentrations, it consistent-ly reduced the total accumulation of primary and secondary metabolites per berry and per plant, with different intensities depending on the genotype. Our results show that WD can ultimately reduce the production of metabolites per unit of fruit and per plant without significantly improving the concentration of compounds of interest in the grape.