Seed banking – is it possible for macadamias?

MCT is contributing fresh macadamia nuts to the RainforestSeed Conservation Project of the Royal Botanic Garden Sydney. Most wild and cultivated varieties of our major food crops are zealously stored in seed banks across the world, but what about macadamias? Rainforest seeds are not easy to store long-term, but researchers are working out techniques so that rainforest species can be added to our stores of grains and vegetables.

 It is comforting to know that there are global organisations such as CropTrust storing examples of the world’s biodiversity in secure seed banks. This is an invaluable resource for our long-term food security as well as for protecting biodiversity but large, oily seeds like macadamias pose a challenge.  They are not as easy to store as grain crops like wheat and rice - in some cases, rainforest species can only be stored as living plants, like the ex-situ plantings of Macadamia jansenii, or as frozengermplasm, which is currently an expensive option. The Royal Botanic Garden Sydney science team is addressing this challenge through a six-year project, and in May 2018 started experiments on macadamias seeds.

 The macadamia project will look at the germination potential of fresh seed compared with germination of:

  1. seed dried to 5% moisture content
  2. seed dried to 15% moisture content
  3. seed dried and then stored for one month at 4°C
  4. seed dried and stored for one month at -20°C.

Seeds at the three different moisture contents (full, 15% and 5%) will also be run through a Differential Scanning Calorimeter, a machine that gradually lowers the seed temperature to -150°C then raises it again to around +40°C, recording any sudden release of energy as the seed freezes, and absorption of energy as the seed thaws. The results will give insights into the temperatures at which macadamia oil inside the seed freezes and thaws, which will help determine the best temperature to try for long term storage.

MCT Executive Officer Denise Bond has sent 500 nuts to Sydney for the experiment. A full report on the project will be prepared for the MCT website.

Please remember to donate to the Trust when you renew your membership and/or contribute to our NIS drive – your donations keep macadamia research and conservation happening.

For more information on the Trust, visit the website www.wildmacadamias.org.au

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This website has been partly funded by Hort Innovation, using the macadamia research and development levy and contributions from the Australian Government.