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April / May 2023

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SA Fruit Journal: April / May 2023

Ecophysiologists join forces with engineers to support precision orchard management. By Anna Mouton

Prof Luca Corelli Grappadelli leads the Ecophysiology Laboratory in the Department of Agricultural and Food Sciences at the University of Bologna in Italy. Ecophysiologists study the interactions of organisms with their environment.

Corelli Grappadelli recently presented a keynote address at the International Pear Symposium in Stellenbosch. "I give all aspects of the Symposium very high marks," says Corelli Grappadelli. "It's also been an eye-opener on the potential of the pear industry in South Africa. We've heard about sustained yields that we don't even dream of achieving."

But he also recognises the climate-related challenges faced by South African growers. "Italy is beginning to have the problems you have had for many years – warm winters, lack of chilling, or maybe sufficient chilling but then protracted blooming and things like that."

Our shared climatic predicament is one reason Corelli Grappadelli spent several weeks in the Department of Horticultural Sciences at Stellenbosch University (SU) after the Symposium.

"Years ago, an Australian grower said to me, we go to South Africa because we find very smart solutions to problems," says Corelli Grappadelli. "I hope to have the opportunity to learn more about your problems and the solutions you have been working on."

Tracking fruit diameter with Wi-Fi

Corelli Grappadelli was initially invited to SU by Prof Karen Theron when she was the head of the Department of Horticultural Sciences, but COVID-19 disrupted their plans.

Subsequently, Alessandro Bonora, one of his students, came to SA to work with Dr Elke Crouch, Postharvest Physiology Research Chair in Deciduous Fruit at SU.

"This rekindled the interest in the exchange," recalls Corelli Grappadelli. Serendipitously, his visit coincided with that of Prof Bart Nicolaï, head of the Postharvest Research Group within the Biosystems Department at the University of Leuven, and Corelli Grappadelli looked forward to brainstorming with Nicolaï and Crouch.

The scientific programme for his visit included deploying a Wi-Fi network connected to fruit gauges in pear orchards. Fruit gauges measure the diameter of fruit with an incredible accuracy of 20 micrometres – a micrometre is a 1 000th of a millimetre. Continuous measurement of fruit diameter tracks daily cycles of water movement relating to tree water status.

Corelli Grappadelli worked with Dr Sebinasi Dzikiti, who runs irrigation trials on pears. "It's an opportunity to study vascular flows in your climate," he notes.

The other aspect of his scientific programme was the measurement of photosynthesis. "We know how critical it is to take photosynthesis measurements as fast as you can when you run irrigation trials," says Corelli Grappadelli. "But even with the state-of-the-art equipment available to Seb, it takes about three minutes per leaf."

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