Rootstock regulation of scion phenotypes: the relationship between rootstock parentage and petiole mineral concentration

Abstract

Context and purpose of the study – Grapevine is grown grafted in most of the world largely because of Phylloxera. Rootstocks not only provide tolerance to Phylloxera, but also ensure the supply of water and mineral nutrients to the scion. Rootstocks are an important means of adaptation to environmental conditions if we want to conserve the typical features of the currently used scion genotypes. To aid this adaptation, we can exploit the large diversity of rootstocks used worldwide. To fully explore this existing rootstock diversity, this work benefits from the unique GreffAdapt vineyard, in which four scion genotypes were studied onto 55 commercial rootstocks in three blocks. The aim of this study was to characterise rootstock regulation of scion mineral status and how it relates to scion development.

Material and methods – Vitis vinifera cvs. Cabernet-Sauvignon, Pinot noir, Syrah and Ugni blanc were grafted onto 55 different rootstock genotypes and planted in a vineyard as three replicates of five plants. The experimental vineyard is located on a sandy gravelly soil at la Grande Ferrade near Bordeaux, France (44°47’26.7″N 0°34’26.5″W). In 2020 and 2021, petioles were collected in the cluster zone with six replicates per combination. Petiolar concentrations of 13 mineral elements (N, P, K, S, Mg, Ca, Na, B, Zn, Mn, Fe, Cu, Al) were determined at veraison. In 2020 and 2021, winter cane pruning weight, vigour, leaf chlorophyll content, fertility and yield were measured. In 2021, Mg deficiency severity was visually scored on each plant; these observations were qualitative and a score between 0 and 3 was assigned. Rootstocks were also grouped according to their parentage when at least 50 % of a Vitis species was present. Data were analysed according to these genetic groups in order to determine whether the petiole mineral composition could be related to the genetic parentage of the rootstock.

Results – Scion, rootstock and their interaction explained the same proportion of the phenotypic variance for most mineral elements. Rootstock genotype showed a significant influence on the petiole mineral element composition. Rootstock effect explained from 8 % for Al to 42 % for S of the variance and an important part for Mg with 35 %. The genetic background V. riparia seems to increase the probability of low P and Mg content. Petiole Mg measurements were related to Mg deficiency symptoms. Severity of Mg deficiency symptoms varied depending on the scion cultivar. The differences in mineral status conferred by rootstocks did not show significant correlations with vigour or fertility.

Significance of the study – This unique experimental design has shown that the rootstock effect is higher than the scion effect on the concentration of large majority of mineral elements in the petiole. The evaluation of Mg levels by petiole analysis and observations of the intensity of deficiency symptoms shows for the first time the variability of the thresholds of satisfactory mineral nutrition between grapevine cultivars. Therefore, fertilization management have to take the rootstock into account.