the origins of the macadamia

[Ken Gargett]

couple of pieces on the macadamia nut. interesting as when we were kids, never heard the name 'macadamia'. they were simply called queensland nuts. most backyards i knew had a tree or two. loved the nuts but they were an absolute bastard to crack open. and many people got rid of them because they caused too much damage to mowers and the mowers would also fling them out like missiles and eyes were in danger, not to mention windows. 

Nut of note: 70% of world's macadamia can be traced back to single Australian tree

New research shows a single 19th century tree in southern Queensland gave rise to the world’s dominant plant variety

Sat 1 Jun 2019

The world’s dominant commercial macadamia cultivar – grown in Hawaii – originated from a single tree in southern Queensland. Photograph: Alamy

The small Queensland town of Gympie has been identified as the origin of 70% of the world’s macadamia nuts.

New research into the fatty seed has revealed the world’s dominant commercial cultivar – grown in Hawaii – originated from a single tree in southern Queensland from the 19th century.

Native to Australia, macadamia trees are only found naturally in southern Queensland and northern New South Wales. The Hawaiian macadamia industry was grown from one cultivar from Australia that was repeatedly cloned.

This means the commercial macadamia tree has an incredibly low genetic diversity, and researchers hope their findings will spur the discovery of wild trees and more “novel genes”.

Genetic diversity would improve crop productivity, increase disease resistance and enable macadamia to be grown in new places, said one of the researchers, Dr Craig Hardner.

By looking at genetic markers, Hardner, from the University of Queensland, and Dr Catherine Nock, from Southern Cross University, traced the origins of Hawaii’s whole industry back to Queensland.

The Hawaiian cultivar had distinctive gene markers in common with a tiny crop of trees in the small locality of Mooloo, near Gympie, 160km north of the state capital Brisbane. Historical records showed that seeds from these trees were taken to Honolulu in 1896.

Despite being found in a narrow band of subtropical rainforest, Australia’s native macadamia had a rich diversity compared with the commercial crops, Hardner said.

This means there is hope for diverse genes to be discovered in Australian forests and even in backyards.

“There is a really strong geographic pattern,” he said. “All the diversity that exists comes from south-east Queensland and northern NSW. Certainly the Hawaiian germplasm is very narrow, so it has only come from one locality.”

The researchers found that some unique genetic markers in commercial trees could not be matched with known wild trees.

 

Hardner said this meant either those diverse genes had been lost in the wild, through land clearing, or that they continued to exist in domestic cultivated plants.

“We suggested maybe some of that diversity that has been lost is in cultivated plants, parks, gardens or people’s backyards,” he said.

The oldest known cultivated macadamia tree is in Brisbane’s city botanic gardens, first planted in 1858.

Hardner said the next step was to focus on forest conservation.

“There’s climate change happening, there is clearing happening, and about 90% of the wild population is on private property,” he said. “It’s really important to identify where there are unique genes in the wild and prioritise those populations for conservation.

“Macadamias are only a few generations from the wild. They have not gone through as many cycles of selection as, for example, apples. This means there is still a lot of opportunity to improve them.”

Macadamias are a major export crop for Australia. In 2017, they made up 14% of the value of all horticultural exports.

 

 

 

 

70 Percent of the World’s Macadamia Nuts Came From One Tree in Australia

Call it the Genghis Khan of macadamias.

by Sabrina Imbler

June 03, 2019

13,486

Behold the macadamia: delicious, fatty, and frequently cloned! Jessica Merz/CC by 2.0

Last week, a shocking discovery rattled the relatively stagnant field of commercial macadamia nut research. The vast majority of the world’s commercial macadamia crops originated from a single 19th-century tree in the tiny town of Gympie in Queensland, Australia, according to a new study in Frontiers in Plant Science. It’s basically the Genghis Khan of macadamia nut trees, progeny-wise.

The researchers collected hundreds of DNA samples from macadamia trees in the trees’ native habitat in Queensland and compared them to samples of commercially grown trees from Hawaiʻi, which produces 70 percent of the world’s macadamia varieties. This comparison revealed that all of Hawaiʻi’s macadamias share distinctive markers with a tiny wild grouping of trees in Gympie, suggesting that all of the state’s modern crops were likely cloned out of a single Australian tree. In other words, 70 percent of the world’s macadamia varieties can be sourced back to a single tree or a couple of trees in Gympie, according to a statement from Craig Hardner, a horticulturalist at the University of Queensland and one of the researchers leading the study.

“A small collection of seeds were taken to Hawaiʻi at the end of the 19th century and historical records suggest that there was maybe six trees grown from that sample of nuts that were taken by Robert Jordan and planted in his brothers’ backyard in the suburbs of Honolulu in 1896,” Hardner told ABC News.

A grove of macadamia trees in Queensland, Australia. Jenny Brown/CC by 2.0

Like many tree crops, macadamias are reproduced via grafting. So commercial orchards often contain thousands of trees but just a few individuals, according to the study. This remarkable lack of genetic diversity places macadamia crops at a higher risk of succumbing to disease or changes in climate than trees with a more diverse population, according to a report in The Guardian. In comparison, wild Australian macadamias boast a rich diversity despite their narrow habitat of subtropical forest, the study found.

Macadamias are no small affair for Queensland. In the 1860s, King Jacky, the Aboriginal elder of the Logan River Clan and the world’s first “macadamia nut entrepreneur,” was the first to commercially market the nut to settlers. The world’s oldest known cultivated macadamia nut tree, planted in 1858, still grows in Brisbane’s botanic gardens. In 2017, the nuts comprised 14 percent of the Australia’s horticultural exports, according to The Guardian. Queensland has paid fitting tribute to its nut-spreading legacy in the form of the Big Macadamia Nut. The nut, which stands 52 feet tall, is one of Australia’s 50 Big Things, which include other fruits such as a Big Bunch of Bananas and a Big Avocado.

 

Of the four wild macadamia species living in Queensland today, three are threatened and one is endangered, the study notes. While collecting samples, the researchers stumbled upon one tree grown in Hawaiʻi that they were unable to trace back to the wild. So they’ve asked local, would-be nut-spotters to get involved in identifying old, wild macadamia nut trees that could hold this missing genetic diversity. So if you happen by Queensland anytime soon and spot the telltale strands of green nuts hanging from a tree, send a leaf sample here and you may help preserve Australia’s fattiest wild nuts.