Production of genetically improved Eucalyptus nitens seed for reforestation

Summary

Eucalyptus nitens is generally regarded as a poor seed producer on an individual tree basis, and until recently natural seed production from E. nitens seed stands and seed orchards has been disappointing. Moreover vegetative propagation of E. nitens has proved to be difficult and until this problem can be overcome, seed remains the only viable option for planting programmes.

We are developing a clearer understanding of mechanisms that control floral induction in E. nitens and this has helped to provide the basis for a more intensive management of seed production. The use of growth retardants in orchards has proved a useful method to increase production of genetically improved seed. Containerised systems, although expensive to manage, offer the most efficient method to produce controlled-pollinated (CP) seed. Control of the level of selfing, by chemical emasculation, could ensure the production of outcrossed seed. Screening of progeny using molecular markers to seek desirable traits should enable the early selection of elite material for use in seed orchards.

While seed orchards continue to be an important source of improved seed, ongoing research is required to optimise orchard management and capture potential genetic gains. A summary of different techniques to produce genetically improved seed is provided so that one can compare and contrast the advantages and disadvantages of each technique. Several improvements in techniques are suggested.