Genetic variations of acidity in grape berries are controlled by the interplay between organic acids and potassium

Abstract

Key message In a grapevine segregating population, genomic regions governing berry pH were identified, paving the way for breeding new grapevine varieties best adapted to a warming climate. Abstract As a consequence of global warming, grapevine berry acidity is expected to dramatically decrease. Adapting grapevine (Vitis vinifera L.) varieties to the climatic conditions of the future requires a better understanding of the genetic architecture of acidity-related traits. For this purpose, we studied during five growing seasons 120 individuals from a grapevine biparental cross. Each offspring was genotyped by simple sequence repeats markers and by hybridization on a 20-K Grapevine Illumina ® SNP chip. Quantitative trait loci (QTLs) for pH colocalized with QTLs for the ratio between potassium and tartaric acid concentrations, on chromosomes 10, 11 and 13. Strong QTLs for malic acid concentration or for the malic acid-to-tartaric acid ratio, on chromosomes 6 and 8, were not associated with variations of pH but can be useful for controlling pH stability under high temperatures. Our study highlights the interdependency between acidity parameters and consequently the constraints and degrees of freedom for designing grapevine genotypes better adapted to the expected warmer climatic conditions. In particular, it is possible to create grapevine genotypes with a high berry acidity as the result of both high tartaric acid concentrations and low K + accumulation capacities.

Vitis vinifera L. Diversity for Cations and Acidity Is Suitable for Breeding Fruits Coping With Climate Warming

“…In this respect, the Petit Manseng, a variety which accumulates a huge amount of sugars in the fruit (Bigard et al, 2018) only exhibited little variations of K + concentration during ripening. This observation doesn't support the hypothesis of an interdependent import of sugars and K + during ripening (Coetzee et al, 2019;Duchene et al, 2020;Nieves-Cordones et al, 2020). Because the berries shrivel after the arrest of phloem unloading (Du Plessis, 1984;Bigard et al, 2019), an important part of the co-variations of sugars and K+ concentration during ripening could be linked to water loss.…”

“…A cluster is composed of berries at different developmental stages ( Coombe, 1992 ; Shahood, 2017 ; Bigard et al., 2019 ; Shahood et al., 2019 ). In genetic and most physiological studies, a grape phenological stage corresponds to a mix of berries representing the heterogeneity of the fruits at plot level ( Preiner et al., 2013 ; Houel et al., 2015 ; Yinshan et al., 2017 ; Duchêne et al., 2020 ). Obviously, the concept of developmental stage remains equivocal in such heterogeneous samples.…”

“…This result is now confirmed from a genetic point of view. Consequently, it seems rather unlikely that the selection of low K + accumulator genotypes would help in reducing the excessive sugar concentrations triggered by global warming, as proposed by Duchêne et al. (2020) .…”

Biosynthesis and Cellular Functions of Tartaric Acid in Grapevines

“…The search for QTLs relating to grape berry acidity has seen a lot of activity in the last decade, with some promising breakthroughs for total or titratable acidity (Liang et al, 2011;Duchêne et al, 2014;Ban, 2016), pH (Viana et al, 2013;Chen et al, 2015), MA (Chen et al, 2015;Duchêne et al, 2020) and various acid ratios in young berries (Houel et al, 2015), however in most cases there was no satisfactory marker for TA level (Liang et al, 2011;Viana et al, 2013;Chen et al, 2015;Bayo-Canha et al, 2019). This may be due to the involvement of several biochemical steps and potential sites of regulation, as well as other factors that affect berry acid levels such as potassium accumulation (Duchêne et al, 2020). Despite these challenges, two major QTLs for TA concentration on linkage groups LG7 and LG4 were stably detected using a Picovine x Ugni Blanc flb population under different environmental conditions (Houel et al, 2015).…”

“…Relevant QTLs from Houel et al (2015) include: ToAG, total acids at green lag phase; TaG: tartrate at green lag phase; MOG: malate/total acids ratio at green lag phase; MTG, malate/tartrate ratio at green lag phase; and TOG, tartrate/total acids ratio at green lag phase. Relevant QTLs from Duchêne et al (2020) include: MT, malate/total acids ratio in green berries (Riesling); pH_S2, pH in mid-ripening berries (Gewurztraminer); TA, tartaric acid concentration; KTA, potassium/tartaric acid ratio in berries (Gewurztraminer). For the full lists of co-expressed genes, refer to Wong (2020) supplementary data at https://sites.google.com/view/vtc-agg.…”