Queensland scientists have successfully grown avocado trees from frozen stems in a world-first for the field of cryo-preservation.
The team at the University of Queensland (UQ) used liquid nitrogen to freeze two types of avocado cultivars for around two weeks. They then brought the frozen stems ‘back to life’ to grow small avocado trees.
While it had been used to bring back bananas, grape vines and apples, it hadn’t yet been figured out for the humble avocado.
UQ PhD student Chris O’Brien, who developed the study now published in Plant Cell, Tissue and Organ Culture, explained the discovery could help to ensure the avocados existence for future generations if something unforeseen were to wipe it out.
“The aim is to preserve important avocado cultivars and key genetic traits from possible destruction by threats like bushfires, pests and disease such as laurel wilt — a fungus which has the capacity to wipe out all the avocado germplasm in Florida,” O’Brien said in a media release.
“Liquid nitrogen does not require any electricity to maintain its temperature, so by successfully freeze avocado germplasm, it’s an effective way of preserving clonal plant material for an indefinite period.”
Bringing an avocado back from the dead
O’Brien placed the avocado stems on an aluminium foil strip, then popped them into ‘cryotubes’ before submerging them in liquid nitrogen.
After being in the liquid nitrogen, it was time to bring them back. To revive them, the stems are pulled out of their frozen state and placed on a petri dish containing a sugary mixture that rehydrates them.
“It takes about 20 minutes to recover them,” O’Brien said.
“In about two months they have new leaves and are ready for rooting before beginning a life in the orchard.”
This technique saw an 80% success rate with the Reed variety of avocado plants while 60% of the Velvick avocados made it back.
There are now 80 successfully thriving avocado plants that faced the big freeze and came back to tell their tales. They’re being housed and monitored in a UQ glasshouse for further observations.
While there are some sci-fi inspired applications of the new discovery, UQ Professor Neena Mitter, who worked with O’Brien, explained its future use will be a bit more down to earth.
“I suppose you could say they are space-age avocados — ready to be cryo-frozen and shipped to Mars when human flight becomes possible,” Professor Mitter said.
“But it is really about protecting the world’s avocado supplies here on earth and ensuring we meet the demand of current and future generations for their smashed ‘avo’ on toast.”
Long live zombified smashed avocados.