Hawaii's macadamia nut industry owes its success to one tree

Today, macadamia nuts are a $3 billion industry, and a single healthy tree can yield 12 to 13 kilograms of in-shell nuts.

Although the fast-growing evergreen tree has become a popular crop in Hawaii, supplying 70 percent of the world’s macadamia nut varieties, the macadamia nut tree originates from Australia.

Researchers from the University of Queensland traced Hawaii’s macadamia tree nut crop back to one single cultivar that was brought to the region from a small town in Queensland, Australia and cloned repeatedly.

Understanding the geographic origins and genetic lineage of a crop can help with conservation and breeding healthier plants that are drought and pest-resistant.

However, the origins of many of our most basic food crop staples remain unknown.

In a new study published in the journal Frontiers, researchers were able to trace Hawaii’s Macadamia nut family tree back to one or several trees from the town of Gympie which was brought to Hawaii in the 19th century.

“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, at Mooloo, north-west of Gympie,’ said Dr. Craig Hardner, a lead author of the study.

Macadamia trees were likely an essential part of the diet of Australia’s indigenous people, but it wasn’t until 1848 that Europeans first recorded coming in contact with the tree and its nuts.

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

What sets the Macadamia tree apart from other popular crops is that the Macadamia nut industry has only recently undergone a massive and rapid global expansion in the last 50 years.

Because Hawaii’s crop is based on one cultivar that was cloned for generations, there is very little genetic diversity in the trees, which makes it easier to trace its cultivar origins.

The researchers conducted a phylogenetic analysis of 64 wild and cultivated macadamia tree samples.

Most of the samples collected from Hawaiin trees shared a chlorotype with trees that grew in the wild in Mooloo.

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

—

By Kay Vandette, Earth.com Staff Writer

Image Credit: Trevor Christopher