Genetic architecture of the tolerance to water deficit in a perennial fruit species (V. vinifera) – G2WAS

In perennial species, yield and production quality are impacted by water stress with marked interannual effects. The knowledge of the physiological and genetic mechanisms regulating grapevine responses to WD remain largely insufficient to adapt the viticulture to climatic challenges. Most often, responses to water stress have been studied during a single vegetative cycle, considering traits independently and using a limited range of genetic diversity.
The G2WAS project aims to study the responses of grapevine to water deficit on intra- and inter-annual scales, by integrating the dynamics of production, storage and utilization of carbon resources in both vegetative and reproductive systems. This study will be performed with a diversity panel designed to maximize the genetic diversity of the cultivated species (V. vinifera). In order to decipher the genetic and physiological bases of adaptation to drought, and to incorporate them into breeding programs, several innovative approaches will be run: i) advanced phenotyping of vegetative and reproductive organs targeted at several critical developmental stages, with a focus on carbon allocation, ii) identification by exhaustive transcriptomics (RNAseq) of co-regulated gene networks; iii) genotype-phenotype whole genome association (GWAS) analysis applied to a panel of 279 varieties iv) development of a multi-trait and multi-year statistical model to improve prediction accuracy. Performed for the first time in perennials, such a combination of methods will improve the detection of QTL and the prediction of individual genetic values.
This multidisciplinary approach will be supported by the G2WAS consortium which brings together specialists in eco-physiology, physiology, quantitative and functional genetics, statistics and breeders. In addition to the coordination (WP1), the project is based on 4 WP: a physiological study (WP2) of 16 contrasting genotypes confronted to a gradient of 10 hydric conditions under tightly controlled environment (PhenoDyn platform) to provide a precise description of the responses to water deficit and to parametrize the conditions to apply to the GWAS panel (WP3) in the semi-automated phenotyping platform (PhenoArch platform); these data will be used for QTL detection and genomic prediction (WP4), using a statistical model specifically developed for this study; finally, the results will be used in ongoing selection programs (WP5). This last step will be one of the first attempts to combine properties of tolerance to water stress and resistance to fungi, in agreement with the 2 major challenges facing viticulture.
In addition to an expected breakthrough on the characterization of critical genetic resources which are fundamental for grapevine improvement, this study will provide new clues on the interaction between carbon limitation and hydraulic functioning at the plant scale. This progress will be essential to develop improvement strategies to anticipate some of the drawbacks linked to climate changes, in particular the increase of evaporative demand and the limitation of water resources. This knowledge and methodologies will be potentially transferable to other models of perennial fruit species.