Accumulation of deleterious mutations in grapevine and its relationship with traits of interest for wine production and resilience

Abstract

Deleterious mutations that severely reduce population fitness are rapidly removed from the gene pool by purifying selection. However, evolutionary drivers such as genetic drift brought about by demographic bottlenecks may comprise its efficacy by allowing deleterious mutations to accumulate, thereby limiting the adaptive potential of populations. Moreover, positive selection can hitchhike mildly deleterious mutations due to linkage caused by lack of recombination. Similarly, in the context of species domestication, artificial selection mimics these evolutionary processes, which can have undesirable consequences for production and resilience. In this study, we evaluated the extent of the accumulation of deleterious mutations and the magnitude of their effects (also known as genetic load) at the whole-genome scale for ca. 500 grapevines including both wild Vitis species originated in three geographical regions (North America, Asia and Europe), and commercial varieties of V. vinifera ssp. sativa (using Illumina paired-end sequencing 20x from the 4k project^[1]). We comparatively estimated the overall efficacy of selection as the ratio of non-synonymous to synonymous mutations in protein coding regions. We also performed various functional prediction analyses on the genomic sequence data to identify deleterious alleles and their effect on gene expression to quantify genetic load. In addition, 40 of the sequenced grapevine varieties were evaluated in an experimental common garden in Bordeaux (VitAdapt^[2]). We obtained phenotypic traits related to wine productivity and resilience (e.g., phenology, biomass growth, water use efficiency and grape production) which allowed to analyse the correlation between the estimated genetic load and phenotypes. The results obtained from this work will contribute to the understanding of how we can best account for deleterious alleles and genetic load in new-generation grapevine breeding.

Acknowledgements: This study received financial support from the French government in the framework of the IdEX Bordeaux University “Investments for the Future” program / GPR Bordeaux Plant Sciences, and from the University of Bordeaux (PurVitis project).

1)  Dong, Y.,et al. (2023). Dual domestications and origin of traits in grapevine evolution. Science, 379(6635), 892‑901.