Two tropical Australian Acacia species (A. mangium and A. auriculiformis) are currently very prominent in industrial plantations and agroforestry programs in Indonesia, Malaysia and the Philippines, and the latter is also important in Thailand. For example, Indonesia alone uses an estimated 500kg of A. mangium seed a year. In addition, trials of these and other tropical acacias are being established throughout southern Asia.
Early plantings in Sabah, East Malaysia, indicated the potential of the leguminous A. mangium as a plantation species, especially for rehabilitating difficult sites and revegetating newly cleared land. It has relatively good form, fast growth on good sites, outstanding ability to compete with weeds of the region and wide adaptability. Moreover, it will grow on soils with a pH as low as 4.0, which is important because acidic soils are widespread in the tropics.
In one of the earliest plantings, at Ulu Kukut in Sabah, A. mangium was planted close to A. auriculiformis. Some of the resultant hybrids - evident in stands originating from Ulu Kukut seed - have better form than A. auriculiformis and lighter branching and smoother bark than A. mangium. Hybrids may thus be more vigorous than the two parents and combine other desirable properties. However, hybridisation in acacias presents some problems, and the use of hybrid clones may be hampered by a lack of techniques for mass vegetative propagation.
The present project will seek to develop reliable methodology for manipulated hybridisation of tropical acacias - as a basis for genetic improvement programs - and to evaluate potential for open pollinated hybridisation in seed orchards. it will also try to develop methods for mass vegetative propagation of tropical Acacia species and their hybrids as a means of capturing the genetic gain from those programs.
Successful manipulation of hybrids depends on a thorough understanding of the floral biology of the species. Australian scientists will study morphology, anatomy, temporal development and incompatibility systems, using electron microscopy techniques on potted experimental material.
The Malaysian team will conduct complementary field work in Malaysia to study floral phenology and the functional pollinating insects. They will also develop skills in isozyme analysis and apply these to the problem of estimating rates of hybridisation in inter-planted mixtures of A. mangium and A. auriculiformis.
Results should confer great economic benefits throughout the region, not only increasing plantation yields of industrial wood but assisting the reclamation of wasteland through reforestation programs.