Evolution of grapevine (Vitis vinifera L.) berry heterogeneity during ripening

UMR AGAP - équipe DAAV (Diversité, adaptation et amélioration de la vigne)The timing of grape picking is a critical point for to production of high quality wines. Berry growth and major solutes are routinely measured on a mix of randomly sampled berries, in order to characterize the advancement of ripening at the vineyard scale, and optimize the date of harvest with respect to the specific conditions of the millesime. Most if not all knowledge on grape berry metabolism emerged from this procedure. Since berries do not ripen simultaneously, averaging induces a statistical bias leading tounderestimation of water, sugars and organic acids fluxes in individual berries. Moreover, detachment of fruits not only blocks sugar import whose speed, even underestimated, largely exceeds the measured variable, but also reverses the direction of vacuolar transport. The influence of temperature on the nature of the respiratory substrate and on global carbon balance needs to be revisited because of these two possible artefacts.This preliminary study aims at evaluating the heterogeneity of developing berries and to decipher the relations between growth, sugar storage, and malate breakdown, at the cluster and berry levels, rather than on the average population. The scattering of sugars and malic acid concentrations shows that heterogeneity among berries is maximal at veraison. Berry volume shows considerable variationwithin and between clusters and doubles during the first period of sugar accumulation, while malate disappears. Sugar accumulation then continues at a constant volume (rate?), and its concentration tends to homogenize during this process, whilemalate content is maintained at a very low value. Finally, phloem unloading completely stops and sugars concentrate as the result of shriveling, malate being totally exhausted at this stage. Preliminary results on respiration show that stopping phloem unloading would increase the O2 demand by 25%

Sugar accumulation and malic degradation uncoupled by temperature in microwine berries

UMR AGAP - équipe DAAV (Diversité, adaptation et amélioration de la vigne)Global warming has already become a critical problem for wine quality in many viticulture regions. However the developmental and molecular mechanisms involved in the response of the grapevine fruit to temperature remain still very elusive. Field experimentation introduces biases in abiotic stress studies on perennial plants such as the grapevine, due to fluctuating uncontrolled conditions. In addition, un-synchronized berry ripening is a major issue that needs to be addressed in abiotic stress studies to reduce experimental noise. In the present study, several long-term temperature treatments were conducted under precisely controlled conditions, using the microvine (DRCF-mutant) as a model. Fruit development and physiology, and the transcriptome adaptation to heat were monitored both at single berry and population levels. Monitoring of the sugar and organic acid content of single berries illustrates that berry heterogeneity within post-véraison clusters spans from plateau herbacé to early maturity, as usually observed on average clusters sequentially sampled along this developmental period. Temperature studies showed an advanced green berry development at higher temperature followed by faster malic acid breakdown during ripening. For the first time in grapevine, we observed a uncoupling of sugar and malic-acid metabolism at the inception of ripening under low temperature. RNA-seq analyses yielded a total of 10 787 temperature-modulated transcripts supporting a range of physiological functions related to primary metabolism. This work, which is the first abiotic stress study on fleshy fruits using RNA-seq for transcriptomic analysis, provides new clues on the mechanisms underlying the metabolic changes caused by temperature during berry developmen

Low temperature delays malate breakdown from sugar accumulation in ripening berries

Low temperature delays malate breakdown from sugar accumulation in ripening berries. 10. ISGP

Temperature impacts on grapevine physiology and development at both plant and organ levels

International audienc

Grapevine physiology and development responses to warm temperatures sensed on the entire plant or on individual bunches

International audienc

Grapevine and climate warming: Duravitis program opens new breeding strategies for temperature adaptation

National audienc

How genetics and breeding do provide options to sustain wine production to face climatic warming issues ?

International audienc

Developmental, molecular and genetic studies on grapevine response to temperature open breeding strategies for adaptation to warming

Aim: In the long term, genetic improvement is one of the major strategies to support sustainable wine production in a changing climate. Over the past 5 years, we have developed an interdisciplinary research program that aimed to: i) characterize the impact of temperature increase sensed by the entire plant or individual bunches on the development and functioning of the plant, ii) identify the physiological and molecular mechanisms regulating the response of vegetative and reproductive development to heat stress and iii) develop tools to map quantitative trait loci (QTLs) of plant and berry development in duly controlled, stable, and contrasting environmental conditions. Methods and results: Performing high-throughput genomic analyses combined with the use of innovative experimental designs (fruiting cuttings, microvines, single berry sampling) was critical to decipher the ecophysiological and molecular mechanisms involved in the vine response to high temperature. Conclusion: Warming promotes vegetative growth and hampers plant carbon balance, disturbing flower set and young berry development. High temperatures modify primary and secondary fruit metabolisms, desynchronizing sugar and organic acid metabolisms and delaying sugar and polyphenol accumulation during ripening. The study of day and night transcriptomic and proteomic signatures associated with heat highlighted key players of the response to temperature in the fruit. Significance and impact of the study: Capitalizing on this knowledge, a new program is being proposed for the selection of cultivars limiting the accumulation of sugars in the berry while maintaining other qualitative compounds