Scientists rush to cryogenically freeze plants at risk from myrtle rust

Researchers are hurrying to cryogenically preserve critically endangered plants at risk due to myrtle rust. Some of the species from the Myrtaceae family are at risk of going extinct in the wild within generations.

“Myrtle rust affects the ability of the worst impacted species to reproduce and some of these species are no longer producing seed in the wild,” said University of Queensland plant molecular physiologist Dr Alice Hayward.

“On top of this, seeds from affected rainforest species often cannot be stored in a seed bank as they don’t survive the standard drying or freezing processes.”

Scientists outlined their approach in paper Plants.

“Many species have been cultivated for their timber, oils, or fruits and are economically valuable both within their country of origin and in plantations around the world,” the researchers write.  

“On-going impacts of land clearing, a changing climate, and myrtle rust on this family mean there is a growing need to conserve species and cultivars.”

“While most dryland genera can be conserved effectively by seed banking, species that no longer produce seeds, or that have desiccation- or freezing-sensitive seeds, require alternative conservation techniques.”

Cryogenically freezing is a process currently used to store animals and human eggs, sperm and embryos, as well as plants like bananas which don’t propagate using seeds.

The process involves providing the plant with protectants, and then quickly freezing cells down to -196°C. Finally, in this case, they’re stored in liquid nitrogen in PlantBank’s cryopreservation tank until they need to be recovered.

However, this technique cannot be used for each plant the same way. Each plant bud or shoot tip needs its own protocol to ensure that the plants can be recovered successfully in the future. For example, the team published research on how to cryopreserve avocado shoots in 2020. Developing each protocol process can take a year or more, all before the material can start to be preserved.

“The project aims to trial everything possible to make it successful for each species – but each species will likely require some specific optimisations for both tissue culture and cryo protocols,” Hayward told Cosmos.

The researchers are targeting a number of plants in the myrtle family, including Lenwebbia spp (main range), Backhousia citriodora (lemon myrtle), Gossia gonoclada (Angle-stemmed Myrtle), Rhodamnia rubescens (scrub stringybark), Rhodomyrtus psidioides (native guava) and Gossia fragrantissima (sweet myrtle).

“Some of the species we are working on are predicted to go extinct in the wild within one generation, with tens of others also critically declining,” Hayward says.

 The researchers are hoping that if they can successfully store these species away from myrtle rust, that others may be able to understand better how to remove or deal with myrtle rust in Australia.

“We are trying to preserve those species that we know are at most risk of extinction in the immediate future, to capture that biodiversity before it’s too late,” says Hayward.

“We are doing something important that can contribute to protecting the unique Australian biodiversity and environment that we call home.”