The roots of South African plant improvement

Horticultural icons Profs Daan Strydom and Gerard Jacobs reflect on the origins of plant improvement and share some of the lessons learnt. By Anna Mouton.

“We initiated plant improvement — virus-free and true-to-type material — with industry in the early sixties,” says Prof. Daan Strydom, who headed the Department of Horticultural Sciences at Stellenbosch University from 1960–1990.

Stopping the propagation of virus-infected plant material was a key motivator. “In those years, people cut bud- and graftwood without a clue of whether or not it was virus-infected,” recalls Prof. Gerard Jacobs, former general manager of SAPO — South African Plant Improvement Organisation — Trust who succeeded Strydom as head of the Department of Horticultural Sciences after the latter retired.

A need to replace seedling with clonal rootstocks was another driver, says Strydom. “Back then, most orchards were planted on seedling rootstocks. That is the worst option — vigorous and variable.”

During his doctoral studies at the University of California, Davis, Strydom gained familiarity with the American approach to plant improvement. Successful plant-improvement systems were also in place at East Malling and Long Ashton Research Stations in England, and Wageningen University in the Netherlands.

“So there were good examples that could show us how to manage it and what was important,” says Strydom. He tapped into this knowledge by inviting foreign experts to visit South Africa and share their insights.

“We began to recognise the opportunity for huge improvements,” remembers Strydom. “It started with the researchers, and we sold industry leaders on the idea.”

The birth of SAPO Trust

The National Department of Agriculture had already begun exploring plant improvement in 1954 and established the South African Plant Improvement Association in 1964.

Meanwhile, representatives from the deciduous-fruit industry boards were co-opted to help drive the process in the private sector: Jan-Linde du Toit for pome and stone fruit, Alex van Niekerk for table grapes, Albert Fullard for canned fruit, and Abraham van Zyl for dried fruit. Plant pathologist Dr Alex Heyns and virologist David Engelbrecht provided scientific inputs.

Their efforts eventually led to the founding of SAPO Trust in 1974 to provide improved plant material to the deciduous-fruit industry. Over time, certain government functions, such as testing for plant viruses, came to reside in SAPO Trust.

The first general manager of SAPO Trust was Dr Jim Button, who served from 1978–1985. Jacobs, who was a senior lecturer in Horticulture at Stellenbosch University, applied for the position, to the dismay of Strydom, his then head of department.

Jacobs led SAPO Trust for nearly three years. “The main focus was on virus diseases, and there were no ELISA tests back then. One tool we had to prevent infections was isolation, so the mother blocks and the stool beds were all centralised on one site, which was bought because it was isolated.” This site was Excelsior — since sold — in the Koue Bokkeveld.

According to Jacobs, he quickly realised that viruses are not the only danger to a plant-improvement programme. One of his first challenges was discovering bacterial infections in their stone-fruit material. Although virus-free, this material could not be sold to nurseries.

Another problem was the unstable colour of bicoloured apples. Orchards established with SAPO Trust material were starting to bear, and the fruit had a poor red colour. As trees with better fruit colour were available in the industry, these became the preferred source of budwood.

SAPO Trust collected budwood in commercial orchards to tide them over, as they needed income from selling plant material to pay the bills. “The apple budwood was visually virus-free, and the industry wants red apples — good colour and visually virus-free takes precedence over proven virus-free status,” comments Jacobs.

He took the approach of developing protocols for each fruit type. New technologies such as ELISA reduced the risk of propagating infected material, while better procedures assured that the material was true-to-type.

Lessons learnt from history

Given their retirement, Strydom and Jacobs are reluctant to offer advice, but they have a few thoughts to share on plant improvement.

“One thing that has helped is importing tissue-culture material,” says Strydom. “That has been an enormous leap forward.” Establishing nucleus units with virus-free plant material can guarantee a clean source from where mother blocks can be renewed regularly.

Jacobs points out that imported material must come from a certified source abroad. “First World facilities for supplying virus-free material are excellent. Then we only need to confirm that there are no pathogens present — this should not be a bottleneck.”

His SAPO Trust experience has convinced Jacobs that, although nucleus material can be centralised, mother blocks should be on multiple sites. “You have to spread your risks,” he stresses.

Both Strydom and Jacobs believe that the rise of plant breeders’ rights had significant implications for plant improvement, including providing an impetus for creating two additional deciduous-fruit Plant Improvement Organisations, TopFruit in 1983 and Stargrow in 1992.

“When I was at SAPO Trust, my argument was that the owners of a cultivar would be sure to look after it,” says Jacobs. “That’s why I pushed for the rights of private nurseries to function as Plant Improvement Organisations and have their own mother blocks. I think it’s unrealistic to think that the licence holders will be prepared to step aside and let someone else manage their mother blocks.”

He also emphasises the need for investment in supporting the establishment of mother blocks in the private sector. “Give them the tools to do the job — provide inspection and testing that doesn’t cost an arm and a leg.”

Looking back, Jacobs says there is far greater awareness of plant-material quality now than when he was at SAPO Trust. “We should acknowledge the significant educational role played by SAPO Trust,” he concludes.