Myrtle rust is a plant disease caused through infection by the fungus Austropuccinia psidii and was first detected in Australia in 2010. The disease has spread through New South Wales, Victoria, Queensland, the Northern Territory, and Tasmania. In this short timeframe, myrtle rust has had a devastating impact on many native species in the family Myrtaceae, including several rainforest species that are now at risk of extinction. In 2022, myrtle rust was first detected in the northern part of Western Australia (WA)-the largest state in Australia. WA is home to ca. 2000 Myrtaceae taxa (ca. 60% of Australia's Myrtaceae diversity), many of which form the dominant component of the vegetation across several ecosystems (e.g., Eucalyptus, Corymbia, Melaleuca, Agonis, Verticordia etc.). While modelling suggests that the environmental conditions in WA's north are less conducive to myrtle rust in comparison to the wet, temperate rainforests of the east coast, WA's temperate, Myrtaceae-rich south coast may be climatically suitable. Coupled with the sheer abundance of Myrtaceae species in WA, their high degree of endemism, high proportion of threatened species, and little available information on their susceptibility to myrtle rust, a pre-emptive strategy to conserve germplasm of at-risk species is warranted. This paper highlights the role of ex situ germplasm conservation in responding to biosecurity threats such as myrtle rust. With early intervention critical to sourcing healthy and genetically diverse germplasm, we present a prioritized list of genera and species of Myrtaceae in WA to inform strategic, coordinated, and timely ex situ conservation actions, along with case studies to illustrate the complementary approaches of seed banking, cryobiotechnology, and tissue culture necessary to conserve germplasm of WA's myrtaceous flora.
Keywords: biosecurity; botanic gardens; cryopreservation; ex situ conservation; seed banking; tissue culture.