Laura Allderman retires

She steps down in December but her contributions to dormancy research will continue to help pome- and stone-fruit growers negotiate climate change for many years to come. By Anna Mouton.

Western Cape winters are getting warmer and the application of rest-breaking agents to mitigate insufficient winter chill is becoming increasingly important. South Africa has been very involved in dormancy and rest-breaking research for many years — not least thanks to the meticulous efforts of Laura Allderman.

Allderman is part of the Hortgro Science team but is seconded to the Department of Horticultural Science at Stellenbosch University.

She studied horticulture at Stellenbosch University and obtained her MSc in 1989 on micropropagation of BP1 and BP3 pear rootstocks under legendary horticulturist Prof. Gerard Jacobs.

“He gave me a book — it was an introduction to tissue culture — and bought some equipment. And then I had to figure it out,” recalls Allderman. She remembers Jacobs as very encouraging. “We had some amazing discussions. The Department in those years was the most incredible place — it was so dynamic.”

After graduation, Allderman worked briefly at the Agricultural Research Council before returning to the University as a contract researcher. “Then we moved to Ceres for two years and that came to an end.”

When Allderman returned to Stellenbosch she had small children and no interest in a full-time job, but the Department was quick to contact her. “Whenever there was a bit of a crisis and they needed someone to do something, they’d call me,” she remembers.

Among other projects, Allderman continued physiologist Dr Nigel Cook’s dormancy research when he left Stellenbosch University for Belgium. This enabled him to complete the project while abroad and led to an ongoing collaboration between Cook and Allderman.

Fifteen years of dormancy research

In 2004, Cook started a five-year project to model dormancy progression in different cultivars, regions, and weather conditions, and Allderman began working half-days as a dormancy researcher. “From then I worked almost entirely on dormancy projects,” she says.

They initially modelled dormancy in Granny Smith and Royal Gala, which showed that different cultivars behave differently, leading them to look at other cultivars and fruit types, as well as rootstocks. More recently, they have investigated the effects of different scion-rootstock combinations on dormancy.

“There’s an interaction there as well,” says Allderman. “If you land up taking a low-chill scion and putting it onto a high-chill rootstock, then you have a problem.” The same applies to a high-chill scion on a low-chill rootstock — one part of the tree starts active growth while the other is still dormant. Allderman believes this is one of the factors that can cause incompatibility between certain scions and rootstocks.

Besides cultivar, dormancy patterns are also affected by region and weather. “Dormancy in a moderate or a marginal climate — our dormancy — is very different to dormancy under ideal conditions, so it’s very difficult to quantify,” explains Allderman. “And every year is different.”

She says that she has certainly seen changes in dormancy patterns over the past 15 years. “Up in the Bokkeveld, in the early 2000s, you could get a typical dormancy curve — under our conditions, the induction period is longer than overseas, but the curve was pretty good. We very seldom get those these days.”

Climate change is leading to increased temperatures and more erratic weather. Hot, dry autumns in the Western Cape delay the onset of dormancy, while hot days in winter disrupt dormancy patterns. Allderman has observed the Bokkeveld becoming more like Elgin used to be 15 years ago.

“It’s becoming more complicated,” she says. “We always had erratic seasons in the Western Cape but it’s just getting worse.”

Scoring 60 000 shoots a week

Up to now, much of dormancy research was underpinned by dormancy curves based on shoot assays. This involves cutting dormant shoots at regular intervals in the orchard and keeping them under constant warm temperatures in the laboratory to measure the time interval until they break bud. The longer it takes, the more dormant the shoot.

Dormancy curves show changes in the level of dormancy over time. Matching laboratory dormancy data to orchard temperature data helps to unravel the relationship between bud-break behaviour and environmental factors such as winter chill.

“The thing about dormancy research is that the methods used are incredibly simple, but the data interpretation is unbelievably complex,” says Dr Esmé Louw, head of the Department of Horticultural Science at Stellenbosch University. “Laura is very comfortable with both roles — the mundane methodology and the unbelievably complex experimental design and data analysis.”

Allderman tells how she and her colleague Ria Rhode scored many thousands of shoots together. “At one stage we were scoring 20 000 shoots three times a week, and it’s not just scoring. You have to change their water and look after them.”

Once she retires, Allderman thinks she might try to work out how many shoots they processed during her career. “I’m glad she didn’t do this earlier,” jokes Louw, “or she might long since have decided enough is enough!”

During the five-year dormancy-model project with Cook, they received shoots every three weeks from February to August from about 30 different growers. One of many examples, according to Allderman, of how much industry supports researchers. “If you had to ask what, over the years, has stood out for me, I would say that it’s the willingness of the farmers to get involved and to help — they are amazing.”

From growth chambers to grandchildren

Although most of her dormancy research was based on shoots, Allderman reports that they have started using potted single-whip trees. “Originally, the research was in the winter months when the roots were dormant and using the shoots without the rootstock was fine for dormancy-curve work. But for researching rest-breaking agents, we’ve found that some years you need the root system as well.”

Allderman initially worked on rest-breaking agents with Jacobs, and then with Louw. Over the years, she has also investigated the effects of plant-growth regulators on dormancy with Cook.

“I hope that the dormancy research continues because there’s so much that still needs to be done,” she says. “But I think if dormancy research has to go forward, the available facilities have to change — the growth chambers that I was using were built before I was born.”

Louw hopes that Allderman will spend some of her retirement setting up a database of all her results. “That would be an incredibly valuable resource. Laura is extremely methodical, and she records everything — the way she approaches her work has always been very special to me.”

Besides missing Allderman’s research skills, Louw says she will also miss her friendship. And, she admits, her baking. “Laura is a legendary brownie baker. It doesn’t matter where you are and in what hole you find yourself, you just need one of Laura’s brownies and the whole world is set right.”

Allderman has nothing but positive things to say about her research career, but she is looking forward to moving on, not least because she has a brand-new vegetable garden, and her first grandchild is due soon. “And,” she adds, “there are lots of mountains calling me to do some hiking.”