SATI Beyond The Bunch 2nd Quarter 2026

However, Ramsey can be too vigorous, especially when paired with a vigorous scion. Should growers prefer a less vigorous rootstock, they can consider SO 4, as it provides similar yields to Ramsey. But their results will depend on their site, as SO 4 can equal Ramsey in vigour under some conditions.

Growers need to take site-specific performance and broader adaptability and stability into account when choosing a rootstock. For example, Ramsey is adaptable, producing high yields in different regions and on a range of soils. This makes it a safe choice, even though it might be outperformed at some sites by rootstocks that are better suited to those particular conditions.

Table 1. Site and trial characteristics for phase 1 (2019–2025). Begin Buffelskraal Denau

Vorentoe

Yarona

Vredendal Olifants River

De Doorns Hex River

De Doorns Hex River

Saron Berg River

Kanoneiland Orange River

Location

Scion cultivar Vine spacing

IFG 68-175 2.7 x 2.0 m

Sugrasixteen

Crimson Seedless

Sugrathirtyfive

Thompson Seedless

3.5 x 1.6 m

3.0 x 1.8 m

3.0 x 2.0 m

3.3 x 1.6 m

0–30 cm

Fine sandy loam Fine sandy loam

Loamy fine sand

Black sandy soil

Loamy fine sand Fine sandy loam Calcareous with white lime and high pH. Micro-sprinklers

30–60 cm Loamy fine sand

Fine sandy loam Alluvial soils. High salinity but optimal pH. Ridged.

Loamy fine sand Loamy fine sand

Soil

Saline with high pH.

Optimal pH.

Leached sand. Optimal pH. Wet conditions.

General

Irrigation system Drip

Drip

Drip

Drip

Trellis system

Gable

Gable

Gable

Gable with nets

Gable

The results of phase 1 are summarised in Tables 3 to 5. The tables show traits that differed significantly between rootstocks overall and at each site. If a trait doesn’t appear in a table, it didn’t differ significantly between rootstocks. In the tables, rootstocks are compared to Ramsey, based on their average performance across all years of phase 1. When considering all the sites combined, the rootstocks showed significant differences in earliness,

yield, bunch and berry mass, and sugar:acid ratio (TSS:TTA). Their relative performance is illustrated in Figures 3 to 5. Note that the letters below the rootstock names indicate statistical difference. For example, in Figure 3, RS-3, RS-9, and Ramsey do not differ significantly in earliness, as indicated by each having the letter a below their names. RS-3 is significantly earlier than SO 4 (and the rootstocks listed to the right of SO 4, none of which have the letter a below their names).

Figure 3. The bud-break earliness of the rootstocks averaged across all sites. Left to right: earliest to latest.

Figure 4. The yields of the rootstocks averaged across all sites. Left to right: lowest to highest yielding..

BEYOND THE BUNCH • 7 • QUARTER 2 • 2026