Harnessing biodiversity to improve grapevine rootstock adaptation to drought

Abstract

Drought is one of the most challenging threats for viticulture because of its impact on reducing yield and on the composition of grapes. In this sense, rootstocks will play a crucial role in improving vineyard resilience to drought because of their functions in water acquisition and transport. However, most of the rootstocks currently used today rely on a narrow genetic background, which could compromise their ability to respond to new environmental conditions. In this work, we aimed to explore the scope for innovation in rootstock adaptation to drought using unexplored wild Vitis species.  For this purpose, we selected a panel of 12 wild Vitis sp (total=50 accessions) present in European germplasm collections. We characterized their adventitious rooting ability and root morphology at different developmental stages (3 weeks, 4 and 7 months) by image analysis. We then explored their response to a moderate and long-lasting drought in controlled conditions, focusing on root morphology, function (i.e. osmotic adjustment) and molecular changes (metabolites and transcripts). We estimated moderate levels of heritability and found varying degrees of intra-specific or inter-specific variation in root morphology. We identified root syndromes correlated with shoot gas exchange responses to drought, maintenance of growth in early stages of drought, and the strategy of root: shoot biomass allocation. In order to explore proxies of root drought responses, we identified root metabolic features from untargeted metabolomic analysis as biomarkers of the genetic variation in root osmotic adjustment. Finally, we identified metabolic and gene expression changes underlying genetic variation of root drought responses among species. The results obtained in this work will help to identify new genetic resources, to be used in rootstocks breeding programs to improve drought adaptation. For instance, V. acerifolia showed promising results regarding its rooting ability and drought responses. In addition, we will provide tools to accelerate the screening of desirable traits in rootstocks using intermediate molecular phenotypes as a proxy of complex root responses.

Acknowledgements

We received funding from INRAE, University of Bordeaux (project MetaRoot), Nouvelle-Aquitaine region (project VitiScope) and CNIV. We acknowledge Maria Lafargue, Cyril Hevin, Nicolas Hocquard, Aurelien Deloume and Martine Donnart, for their help with the plant material and sample preparation.