Impact of genotypic variability on grapevine architecture and light interception: A functional-structural modelling approach

Abstract

Aerial architecture plays a key role in plant functioning as it affects light interception and microclimate. In grapevine, this architecture is primarily shaped by winter pruning and further adjusted through practices such as leaf thinning and topping during the growth cycle. Additionally, substantial variation in architectural traits, such as leaf size and branching intensity, exists among cultivars. While numerous studies have examined the effects of training practices on light interception and microclimate, the impact of genotypic variability remains understudied.

To address this, we defined a set of 16 genotypic parameters, based on measurements from 15 grapevine cultivars, in order to describe architectural differences. These parameters also account for the large variability among shoots of the same cultivar and the spatial heterogeneity in traits (e.g., leaf area, internode length) along individual shoots. We extensively modified the 3D functional-structural model TopVine (Louarn et al. 2008) that was previously validated on Syrah and Grenache cultivars to incorporate these levels of variability.

Simulations revealed a significant impact of cultivar architecture on total light interception and mean leaf irradiance. Notably, a trade-off emerged between total light interception at the plant scale and self-shading within the canopy. High self-shading in the most vigorous cultivars negatively affected photosynthetic activity at the plant scale, as simulated by our model.  Furthermore, the results highlighted the importance of considering both intra- and inter-shoot variability, demonstrating that simulations relying on the replication of homogeneous shoots to represent the entire plant fail do not accurately reflect cultivar-specific differences.

This study provides a robust framework for simulating architectural variability in grapevine and opens new ways for analyzing its impact on plant functioning across a wider range of cultivars.