Evaluation of peach rootstocks for South African fruit industry: Rawsonville planting

The main objective of this project is to evaluate high-potential imported and locally bred rootstocks on high-risk sandy soil in a low-lying area in the Slanghoek, Rawsonville region. The results of the trial will help growers in this and similar growing regions select the best rootstocks for their orchards.

In 2016, a trial was conducted to evaluate 11 rootstocks on sandy/rocky soil with prevalent occurrences of different nematode species and a high water table. The rootstocks were planted as part of a commercial orchard with ‘Earliblush’ as the scion cultivar and the trial layout consisted of a randomised complete-block design with 10 replications. The rootstocks were evaluated over an eight-year period for tree mortality, tree vigour, productivity, yield efficiency, fruit size and quality, and sensory and visual evaluation. These rootstocks included: Barrier, Coast Guard, Flordaguard, Garnem, GF 677, Guardian, Kakamas, OSM 99-2, OSM 99-3, Rootpac-70 and Viking.

Towards the end of the trial Barrier, Coast Guard, Flordaguard, Rootpac-70, and Viking were the  rootstocks that did not lead to any tree deaths. All rootstocks were able to establish into the two-leader training system, and Barrier displayed higher tree vigour than the others. For cumulative yield, Guardian accumulated the highest yield, followed by Barrier, OSM 99-3, OSM 99-2, Coast Guard, Rootpac-70, Viking, and Flordaguard ranking in that order. However, all of the rootstocks produced at least 34 tons/ha of yield per season, so there was no clear superior rootstock in terms of yield. Significant differences in fruit size were found in field sample and laboratory sample conditions, but all of the rootstocks produced fruit that would fall into the size B class for peaches according to the EU size chart. Sensory and visual evaluation did not identify a superior rootstock for consumer experience.

The study found that eight of the eleven rootstocks showed superior yield and could be considered as successors to the industry standard rootstock Kakamas. These rootstocks are Guardian, Barrier, OSM 99-3, OSM 99-2, Coast Guard, Rootpac-70, Viking, and Flordaguard. Rootstock recommendations with strengths and weaknesses are discussed below to provide insight how the eight rootstocks with superior yield differed.

In line with the main objectives of this trial, local and imported rootstocks were evaluated and recommendations can be made for peach producers in the Slanghoek region. Eight clonal rootstocks outperformed the seedling rootstock Kakamas which would suggest the future of peach and nectarine rootstocks are the new generation of clonal rootstocks.

The evaluation results of the trial provided realistic expectations of expected yield, fruit size, fruit quality and consumer perspective of each rootstock included in the trial. Therefore, the trial has provided insight and allows producers to make informed decisions.