Whole-vine resources modify within-vine relationships between growth parameters and metabolites in Vitis vinifera L. cv. Cabernet-Sauvignon

Fruit ripening on a perennial tree or vine is typically asynchronous and rarely investigated. In commerce, this is problematic as it impairs sampling to meet commercial maturity and quality standards at harvest. For grapevines, understanding within-grapevine variability in berry maturity will benefit precision management and harvest planning. It is accepted that variation in maturity is approximately equally allocated at the within- and between-vine scale. However, the mechanistic and ecological factors that cause functional variance are poorly understood and rarely documented. This study aimed to identify structural and spatial within-vine attributes associated with berry composition at harvest related to available resources from the whole grapevine. Vegetative and reproductive biomass attributes within- and between-vines were analysed for cv. Cabernet-Sauvignon trained as a cordon, spur-pruned system using a Smart-Dyson trellis in a `New World' industrial-scale vineyard. The vines were located in northern Margaret River, Western Australia. Variability in soluble solids, anthocyanins and phenolics were analysed for clusters and corresponding canopy characteristics. Berry size was the best predictor of variance in maturity among sugar, anthocyanins and phenolics composition within individual vines. Smaller stems or fruit had greater variation in maturity than larger stems or fruit. However, the relationship between whole plant biomass and fruit maturity interacted at different scales; the first report for grapevines. Including different vine-biomass scales helped explain the heteroscedasticity observed when the individual vine effect was excluded from the analysis. These findings suggest that high vigour grapevines could benefit from differential management, regardless of harvest index. Furthermore, these findings may help explain the diversity of response to treatment effects such as cluster or leaf thinning reported previously for perennial fruit.