Fit for purpose

South African apple growers are leveraging rootstock diversity to adapt and thrive in an increasingly complex industry. By Anna Mouton.

In a 1978 issue of The Deciduous Fruit Grower, Dr Oloff Bergh and co-authors rated M.793 as the top rootstock on most soils. “Today, I suspect very few people in this room would say there isn’t a better rootstock,” said Tristan Dorfling.

Dorfling is the CEO of the independent cultivar-evaluation company Provar and has extensive experience managing Hortgro-funded apple-rootstock trials. He was speaking at the 2026 Hortgro Technical Symposium.

“Rootstocks are changing how we grow apples, design orchards, manage risk, allocate resources, and respond to the challenges facing modern fruit production,” he said. “In that sense, rootstocks are helping reshape the apple industry.”

South Africans do it differently

In recent decades, much of the international apple industry has intensified, adopting higher planting densities of smaller trees on more dwarfing rootstocks. This transition is at least partly driven by labour scarcity and cost.

“South Africa’s response has been somewhat different,” said Dorfling. “We’ve seen diversification. The number of rootstocks available to growers has increased substantially, and the overall rootstock portfolio is far broader.”

He shared PlantSA figures for nursery-tree production from 2016 to 2025. In 2016, M.7 EMLA and MM.109 were the dominant rootstocks, followed by M.793. In 2025, M.793 had all but disappeared, MM.109 had greatly reduced, and M.7 EMLA had shrunk to about 20% of the total. However, this wasn’t because our industry switched to dwarfing rootstocks.

“Vigorous rootstocks still represent a significant proportion of the trees propagated in 2025,” Dorfling pointed out. Indeed, vigorous Geneva rootstocks were about as popular as M.9, semi-vigorous Geneva, and dwarfing Geneva rootstocks combined. Add MM.109, and vigorous rootstocks outnumbered semi-vigorous and dwarfing rootstocks.

“So, unlike many international examples, South Africa has not converged on a single rootstock strategy,” said Dorfling. “Instead, we appear to be moving toward a more diverse rootstock landscape.”

The impact on orchard performance

“The assumption was always that you needed smaller trees to achieve major gains in orchard efficiency and productivity,” said Dorfling. “But, when we look at the data, it’s easy to understand why vigorous rootstocks have not disappeared.”

He was referring to a bubble chart of yield per tree and yield efficiency (in kg per trunk cross-sectional area) for four vigorous rootstocks: MM.109, M.793, G.778, and G.228.

“Despite occupying similar vigour classes, G.778 and G.228 produce nearly three times the cumulative yield of M.793, while maintaining similar tree size,” he said. “Improvements in orchard efficiency are not only occurring through smaller trees, but also through better vigorous rootstocks.”

Further evidence for his argument comes from the industry’s performance. South African apple production has grown from 0.9 million tonnes in 2018 to 1.2 million tonnes in 2024, and the number of cartons passed for export increased from 31.5 million to 48.7 million over the same period (according to Hortgro Key Deciduous Fruit Statistics 2024).

“It’s impossible to attribute this to rootstocks alone,” acknowledged Dorfling. “We’ve seen improvements in cultivars, management practices, irrigation strategies, and production systems, but rootstocks are part of the story.”

Clearly, South African growers are generally making sound rootstock choices. But Dorfling thinks it also suggests that the value created by better rootstock genetics is not confined to the dwarfing class.

Size isn’t everything

Intensification brings obvious opportunities: higher productivity, earlier returns, improved fruit quality and uniformity, and greater labour efficiency. It also places extra demands on growers, for example, additional investment and infrastructure and precision management, while simultaneously reducing the margin for error.

Dorfling doesn’t advocate one approach. “It’s about context,” he said. “Different industries, production environments, or economic realities will lead to different solutions. This might explain why South Africa isn’t following the same rootstock path as other apple-production regions.”

The underlying principle, as Dorfling explained, is that rootstocks influence more than vigour. “Tree size is just the visible outcome of a much broader set of biological and commercial effects,” he said.

Rootstocks affect biology (tree size, precocity, yield efficiency, and fruit quality), system (planting density, trellising, labour efficiency, and production inputs), risk (resilience, climate sensitivity, orchard lifespan, and profitability), and market (pack-outs, harvest timing, fruit value, and market fit).

“When a producer chooses a rootstock, they are not simply choosing how large the tree will become,” said Dorfling. “They are making decisions about their entire orchard system.”

New contexts raise new questions

In another bubble chart, Dorfling contrasted yield per hectare and yield efficiency per tree (kg per trunk cross-sectional area) for different rootstocks across central-leader and staggered-V systems.

“We can see that some rootstocks perform very differently depending on the orchard system,” he said. “A rootstock that appears attractive in one system may become less so in another.”

For example, G.778 outperformed M.7 EMLA, which outperformed G.222, in central leader systems, but all three of these rootstocks performed very similarly in staggered-V systems.

“These data don’t isolate for the training system,” noted Dorfling. “But they reinforce that rootstock performance is unlikely to exist independently of the context in which the rootstock is grown.”

Coming back to Bergh and colleagues, M.793 very well may have reigned supreme in the 1970 context. At the time, the critical questions in evaluating rootstocks focused on tree size, vigour, yield potential, establishment, and broad suitability.

Those questions remain relevant. But, in the new context of 2026, rootstocks are increasingly judged on how well they fit the production site and system. Are they a good match for a particular climate and microclimate, orchard design, set of economic objectives, and risk profile?

“Apple production is not a rootstock problem,” said Dorfling. “It’s a system, and rootstocks are only one component of that system.”

Reshaping apple production

Once we accept that there’s no universally superior rootstock, choosing a rootstock becomes more complicated. Growers must balance multiple interacting factors, such as climate, soil, scion cultivar, orchard design, labour, management capacity, economics, and market demands.

“Two growers operating under different circumstances may quite rationally select different rootstocks, and both make the correct decision,” said Dorfling. “The best rootstock depends on the rest of the system.”

He believes rootstocks are reshaping apple production by expanding growers’ options. Rootstocks expand the available production systems and enable trade-offs, for example, between establishment costs and early yields. They provide the flexibility needed to navigate a progressively complex production and market environment.

“We are very fortunate that the industry understands this, and understands the importance of funding rootstock research,” said Dorfling. He mentioned Hortgro-funded rootstock trials and a collaborative effort by Hortgro and Provar to develop a platform that growers can use to access the most up-to-date rootstock information.

“There is no single right rootstock solution,” he concluded. “So, we need to give growers as much information as possible, so they can slot that into their context, make the best decision, and go forward confidently.”

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Watch this presentation on the Hortgro YouTube channel.