Caption: Dr Craig Hardner, pictured with the world’s first cultivated macadamia tree, planted in the Brisbane Botanical Gardens in 1858.

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THE GLOBAL macadamia industry may have originated from a single tree taken from Gympie to Hawaii in the 19th century, according to new research into macadamia genetics.

“It may have been a single tree, or a couple of trees, taken from Gympie, but that sample was the foundation of the Hawaiian macadamia industry which today supplies around 70 per cent of the world’s macadamias,” said University of Queensland horticultural science researcher, Dr Craig Hardner.

Dr Hardner and Dr Catherine Nock from Southern Cross University have studied the chloroplast genome of macadamia trees in the wild, which is the part of the plant’s DNA that is involved with photosynthesis and how the plant uses energy.

The research team studied the structure of the chloroplast genome from the Hawaiian macadamia industry and mapped it back to trees in the wild.

“What we found was that most of the germplasm in Hawaii and particularly the germplasm used extensively throughout the world for commercial production came from a single population, and possibly even a single tree, from a place called Mooloo, northwest of Gympie,” Dr Hardner said

The tree nut crop macadamia is native to Queensland and northern New South Wales, and modern macadamia production systems are only a few generations removed from the wild.

“Understanding the genetic diversity of macadamia trees in the wild is important because macadamia is a relatively new crop compared to crops like peaches, where many centuries of domestication have helped improve important traits,” Dr Hardner said.

“The potential for improvement for important traits like disease resistance of climate variability is substantial.”

A key finding of the research, which was published in Frontiers in Plant Science, is that significant genetic diversity of wild macadamia has been lost through clearing land since European development from the 19th century.

Although the macadamia nut was likely a component of the diet of the indigenous peoples of Australia, the first recorded European contact with macadamia was in 1848.

“The world’s first cultivated macadamia tree was likely planted in 1858 by Walter Hill in the Brisbane Botanical Gardens, and it is still alive today,” Dr Hardner said.

The genetics of this tree, and two other trees that date back to this era, one planted at the University of California in Berkeley in 1879 and one growing in Dr Hardner’s backyard in Yergona, do not map back to any of the recent samples taken from the wild.

“This suggests that there was some diversity present at the time of European settlement that has been lost to commercial macadamia production systems,” Dr Hardner said.

“We could well find that some old macadamia trees growing in people’s backyards might also have this genetic diversity – like the tree in my backyard.”

He and Dr Nock are working with the Macadamia Conservation Trust, macadamia industry and other stakeholders to sample old trees that people have in their backyards for genetics that have been lost in the wild and to global macadamia production systems.

The global macadamia industry is worth approximately $3 billion and the industry has undergone rapid global expansion in the last 50 years.

Australia, South Africa, Kenya, and the United States are currently the largest producers, and the crop is also cultivated in China, Southeast Asia, South America, Malawi, and New Zealand.

Future growth in global production is predicted following recent extensions in planting, particularly in China and South Africa.

This research has been funded by The University of Queensland, Hort Innovation, Department of Agriculture and Fisheries, and Churchill Trust.

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This article was originally produced by QAAFI Media.