Genetic diversity would improve crop productivity, increase disease resistance and allow macadamia to be grown in new locations, said one of the researchers, Dr. Craig Hardner. The researchers collected hundreds of DNA samples from macadamia trees in the native habitat of trees in Queensland and compared them with samples from trees grown commercially in Hawaii, which produces 70 percent of the world's macadamia varieties. The world's oldest known cultivated macadamia nut tree, planted in 1858, still grows in Brisbane Botanic Gardens.
The Hawaiian macadamia industry was grown from a variety from Australia that was repeatedly cloned. While collecting samples, the researchers stumbled upon a tree that had grown in Hawaii and that they couldn't trace back to its wild state. It wasn't until the early 20th century that macadamia nuts began to be cultivated in Hawaii as a cash crop.