Evaluation of plum rootstocks for the South African fruit industry in association with IP owners at Simondium

The main objective of the stone fruit rootstock evaluation programme is the evaluation of high potential imported and locally bred rootstocks on different soil types and under different climatic conditions. The outcome should include rootstock recommendations that can complement yield and fruit quality for plum production. This trial was specifically targeted at rootstock performance in the Berg River region with wet sandy soil conditions and with high nematode infestation.

At the Simondium trial site, 12 rootstocks were planted in 2015 in a complete randomised trial lay-out in 10 blocks. Trial trees and side row trees were included in a commercial orchard. The new ARC bred rootstock selections OSK 99-6, 7B-25-21 and 5A-05-34 were pre-selected for root-knot and ring nematode resistance. Other rootstocks included in this trial were: Atlas, Flordaguard, Garnem, GF 677, Guardian, Kakamas, Marianna, SAPO 778 and Viking. The rootstocks were evaluated across an eight-year period assessing tree mortality, tree vigour, yield productivity, yield efficiency, fruit size and quality along with sensory and visual evaluation to provide a consumer aspect.

The best tree survival was found with Atlas trees, followed by GF 677 and Viking. 7B-25-21 and Marianna were the most vigorous trees; however, these trees experienced relatively high tree mortality, thus tree vigour was not considered the primary factor for recommendations. GF 677, Atlas and OSK 99-6 ranked first, second and third for cumulative yield respectively. The largest fruit was found on Flordaguard, Garnem, Marianna and Viking, which were categorised as class AA fruit. Other fruit quality traits were too marginal to be considered for commercial recommendations. In terms of sensory and visual evaluation OSK 99-6, Atlas and GF 677 performed above average and may provide a better consumer experience.

Overall, this study showed that GF 677 and Atlas can be recommended for improved cumulative yields with 73% and 72% respectively higher when compared to the control rootstock of plums i.e., Marianna. Despite certain rootstocks with better fruit size, these cannot be recommended due to poor survival and/or limited yield. Recommendations are based largely on tree survival and cumulative yield as these factors were deemed most important to the producer’s income.

In line with the main objectives of this trial, local and imported rootstocks were evaluated and recommendations can be made for producers in the Simondium region farming on soils subject to seasonal high water tables and high nematode populations. Among the tested rootstocks, GF 667 and Atlas demonstrated superior adaptation. This was based on a combination of tree survival, high yields and above average sensory/visual fruit quality. The performance of the certain clonal rootstocks outperformed Marianna in Simondium, the current most frequently used plum rootstock in South Africa. This justifies why producers should buy into new clonal rootstocks to increase survival rate, yield, fruit size and fruit quality.