Clonal maturation of Corymbia torelliana × C. citriodora is delayed by minimal-growth storage

Summary

Minimal-growth storage may be a simple method to preserve germ plasm while tree varieties undergo clonal selection, but there has previously been little evidence to demonstrate that minimal-growth storage delays maturation. This study assessed the maturation of 10 Corymbia torelliana × C. citriodora clones whose shoots had been stored for 12 months using three different methods: (1) as ex-vitro stock plants in the nursery; (2) in-vitro at 25°C; and (3) in-vitro under minimal-growth conditions at 14°C. Minimal-growth storage increased the subsequent frequency of adventitious rooting in cuttings of 6 of the 10 clones, providing increases in rooted cutting production of between 53% and 163% over ex-vitro nursery storage. Minimal-growth storage also increased adventitious root number in two clones and root mass in four clones. C. torelliana × C. citriodora clones underwent maturation during ex vitro stock plant archiving in the nursery, but in-vitro storage under minimal-growth conditions was highly effective in delaying clonal maturation.

Keywords:

• propagation
• adventitious roots
• cuttings
• cool storage
• Eucalyptus
• Myrtaceae

Acknowledgements

We thank David Lee (Agri-Science Queensland) for providing seeds, and Tracey Menzies, Katie Roberts, Nick Evans, Brooke Dwan, Elektra Grant, Laura Simmons, Luke Verstraten, Elisabeth Higgs, Jane Quinn, Philippa Bryant, Bruce Randall, David Walton and John Oostenbrink for technical assistance. This project was funded by the Queensland National and International Research Alliances Program and the Queensland Plantation Hardwoods Research Fund, and supported by a postgraduate scholarship to CDH from the Vietnam Ministry of Education and Training (MoET).