Evaluation of peach and nectarine rootstocks for the South African fruit industry at Vaalwater, Limpopo

The main objective of this trial was to evaluate high-potential imported and locally bred rootstocks at two different planting locations and soil types in the Limpopo, Vaalwater growing region. Boekenhout farm is characterised by sandy loam soil, whilst Waterval has a well drained, high clay soil type. The presence of nematodes in these soils and very early flowering and harvest of the cultivar ‘Snow Angel’ are two aspects to be considered in interpretation of results.

Two plots (Boekenhout and Waterval) were planted during the year 2015 in the Vaalwater region. ‘Snow Angel’ was used as the scion cultivar in both plots. Five rootstocks were included at Boekenhout, whereas nine rootstocks were included at Waterval. The trial layouts of both trials were randomised complete-block designs (ten blocks) with single tree replications. The rootstocks were evaluated over an eight-year period for tree vigour, productivity, yield efficiency, fruit size and quality, and sensory and visual evaluation.

Of the five rootstocks tested at Boekenhout, Okinawa had the highest yield over five years of fruit production, followed closely by Flordaguard and OSM 99-3. The same three rootstocks improved fruit size. The measured fruit quality traits were significantly impacted by the rootstock choice, but the sensory and visual characteristics of the cultivar were not affected. The occurrence of free-living and ring nematodes at Boekenhout were significantly impacted by rootstock.

At Waterval, rootstocks did not significantly impact the average or accumulated yield across the five harvest seasons. Improved fruit size in field conditions was found on Flordaguard, OSM 99-3, Barrier and Okinawa. Measured fruit quality traits were significantly impacted by the rootstock choice. Rootstock choice had no significant impact on subjective fruit sensory and visual evaluation results. The occurrence of pin nematodes was significantly impacted by the type of rootstock.

Overall, the results from the trial indicate three superior rootstocks for the Boekenhout-type soil and growing environment that resulted in the highest production potential, i.e., Okinawa, Flordaguard and OSM 99-3. Kakamas was inferior to the other rootstocks in terms of production potential. For improved fruit quality, Flordaguard or OSM 99-3 were superior.

Despite the similar production and fruit quality attributes between rootstocks at Waterval, it was notable that Flordaguard, OSM 99-3, Barrier and Okinawa produced larger fruit on average. In an environment with a short growing season, the marginal improvements in fruit size of the aforementioned rootstocks can be of benefit for production areas similar to Waterval.

For rootstocks which can perform on either weak or stronger soils in the Vaalwater region, Flordaguard, Okinawa and OSM 99-3 performed well. On weaker soils, these rootstocks improved yield and fruit size when compared to Kakamas. On stronger soils the differences become apparent with better fruit size compared to Kakamas.

Three rootstocks showed promise in Boekenhout’s conditions and the evaluation results provide realistic expectations for yield, fruit size and other measurable fruit quality aspects that are likely to be produced with the selected rootstocks, i.e., Okinawa, Flordaguard and OSM 99-3. The data has provided insight on production and fruit quality traits of the tested rootstocks and allows producers to have some reference when deciding which rootstock(s) to use when planting in sandy loam soils with ring and root-knot nematodes in the Limpopo production area.

For environments more similar to Waterval with higher potential soils, we expect that rootstock differences will be minimised for yield. Recommendations are based on improvements for fruit size. Barrier, Flordaguard, Okinawa and OSM 99-3 produced larger fruit therefore were recommended. For rootstocks which can perform on either marginal or high potential soils in the Vaalwater region, Flordaguard, Okinawa and OSM 99-3 performed well in both environments. On weaker sandy soils, these rootstocks improved yield and fruit size when compared to Kakamas. On stronger soils the differences become apparent with better fruit size compared to Kakamas.