Development of domestication strategies for commercially important species of Meliaceae

• National Agriculture and Forestry Research Institute, Laos
• Forest Science Institute of Vietnam, Vietnam
• Forest Research Institute of Malaysia, Malaysia
• Royal Forest Department, Thailand
• CSIRO Entomology, Australia
• CSIRO Plant Industry, Australia

Forest cover is declining throughout Southeast Asia, as it did in Australia in the early 20th century. Associated with this is a loss in species and a reduction of the genetic diversity within surviving species. Many high-value Australian tree species are now reduced to populations that are too small for commercial exploitation.
Urgent measures are now required to conserve and encourage sustainable use of the forest trees of Southeast Asia, particularly the most valuable timber species. Domesticating tree species is an important step. To do this, it is first necessary to identify and characterise the germplasm resources, and then to acquire, select and manage those so as to cultivate the species in managed ecosystems.
In contrast to fruit trees, which have long been cultivated in Asia, forest timber trees have been little studied, selected or improved. This project attempted to do this, and undertook the first attempt to domesticate a rainforest timber tree in Australia.

The ultimate goal of this project was to enhance the use of selected germplasm of high-value timber species for general social benefit. The research developed ways of domesticating important indigenous forest tree species, to further their conservation.

Two related species were chosen, Chukrasia spp, which occurs in forests from Pakistan to Borneo, and the closely-related Toona ciliata, Australian red cedar. Both species have considerable economic and social importance, and their natural populations have been subject to logging pressure for many years.
The first part of the project involved surveys to ascertain the present distribution of Chukrasia, especially in Vietnam, Lao PDR, Thailand and Malaysia. Then seed was collected from across the species' range. Using this, the researchers established trials to separate out provenances (different varieties from known locations) and then selected the best-performing provenances. In particular, they tested provenances for resistance to insect attack under a range of field conditions. They also assessed genetic variation inherent in the genus.
The researchers also sought to develop ways to propagate the tree vegetatively, particularly studying cuttings, in order to disperse preferred varieties more easily. Finally, they studied the floral biology of both Chukrasia and Toona.

The project made a good start towards the development of Chukrasia as a new forestry/agroforestry species to meet the need for more diversified production systems. It has been established in areas where it can have immediate impact through the dissemination and implementation of the findings. The range-wide seed procurement program was particularly successful and will ensure the availability of genetic material for future tree improvement programs. The study of reproductive biology has provided some basic information of importance for a future breeding program. The project collected much basic information for future development of a domestication strategy for a range of beneficiaries.
The greatly superior performance of Chukrasia in farmers' fields in Vietnam, compared with forestry sites, strongly suggests that the future of this species is in agroforestry.
At the outset knowledge about Chukrasia was very limited, highly scattered and disparate. The preparation of a monograph pulled all the information together. This essential information provides an excellent baseline for planning and undertaking further domestication research.
A study of the floral biology of Toona ciliata revealed that the species is likely to have evolved as a complex response to environment, outbreeding and pollinator requirements. The research results have the potential to help in the development of a breeding program through controlled crossing.
The training aspects of the project were particularly successful. Counterparts now understand the principles of the domestication process, and have developed a high degree of skill in trial establishment and data analysis.