RA5 WEBINAR: Freezing for the future

Freezing for the Future: can seed banking fleshy Myrtaceae seeds buy time in the myrtle rust battle

November 2021

Van der Walt K, J. N. 2021. Freezing for the Future: can seed banking fleshy Myrtaceae seeds buy time in the myrtle rust battle. Beyond Myrtle Rust Webinar. 16/11/2021.

ABSTRACT

Myrtle rust is now established in most of the climatically suitable areas in New Zealand and the future for many of NZ’s native Myrtaceae is unclear. The long-term storage of seed provides an opportunity to secure species and genetic diversity. This provides options for species recovery, future restoration, resistance breeding and research. The first step in the seed banking process is to quantify seed viability, determine germination protocols and establish seedling health. This is followed by a desiccation test. The seed viability and seedling vigour of the desiccated seeds are then compared to fresh seed. Provided these remain similar, the seed can be stored at –18°C. However, some species lose viability following desiccation and/or freezing. For these species, alternative methods such as cryopreservation (storing at –196°C in liquid nitrogen) of the seed, embryos or shoot tips needs to be investigated.

One of the characteristics of desiccation sensitive (recalcitrant) seed is large, fleshy fruit. Karin presents her research into the long-term seed storage options for four native fleshy fruited Myrtaceae species: Lophomyrtus bullata (ramarama), L. obcordata (rōhutu), Neomyrtus pedunculata (rōhutu) and Syzygium maire (swamp maire, maire tawake). For L. bullata, L. obcordata and N. pedunculata, Karin and her team looked at the role of desiccation and storage temperature (5°C, –18°C and –196°C) on seed viability and seedling vigour over 24 months. Syzygium maire seed showed extreme sensitivity to desiccation, suggesting storage will require cryopreservation.