Physiology and genetic improvement of Acacia auriculiformis

• Kasetsart University, Thailand
• Forest Science Institute of Vietnam, Vietnam

Many fast-growing Australian tree species are suited to the plantation forestry and agroforestry needs of tropical Asia and Africa. Acacia auriculiformis is a priority species recommended for extensive development in tropical lowlands with low humidity and high water deficit.

A. auriculiformis occurs naturally in the Northern Territory and northern Queensland in Australia, and the south of the Western Province of Papua New Guinea extending into Irian Jaya in Indonesia. It has a pulpwood potential comparable to high-quality eucalypts. However, most of the trees grown in Asia so far have crooked/forked stems which severely restricts their use. Trees with single straight stems and light crowns have been located in Queensland. Studies in Australia and elsewhere in Southeast Asia have indicated that trees originating in Papua New Guinea have the highest biomass; Queensland trees the best stem form; and NT trees have both poor form and above ground growth.

The major objectives of this project are:

to understand the biological and physiological basis of the growth of trees originating from different areas (provenances) in a number of harsh and arid environments in Australia, Thailand and Vietnam; and

to develop a genetic improvement strategy for the tropical environments. The project will involve collaboration between the Northern Territory University (NTU), Australia, Kasetsart University, Thailand, and the Forest Science Institute, Vietnam.

Research will be done on Melville Island and Howard Spring (near Darwin) in Australia with A. auriculiformis. In Thailand, research will be done at Kachanaburi (< 1000 mm rainfall) and Sakaerat ( ~1200 mm rainfall). Scientists will measure annual height and stem diameter; photosynthesis; leaf water potential, chlorophyll content, nitrogen and area; and weight and nitrogen content of leaf litter for each provenance at each site. F1 hybrid plants will be included in the physiological study when they are 12 years old.

At the end of a dry season, scientists will collect leaf samples, process them at the NTU, and send them to the Australian National University (ANU) for carbon isotope analysis. Stable carbon isotope composition can be related to water-use efficiency (WUE). Shade-house experiments at NTU, are designed to identify genotypes with good growth and high WUE.

Australian researchers will study leaf protein, photosynthetic capacity and mobilisation of nitrogen during new growth. Shoot and root gas exchange in seedlings of each provenance grown at NTU under nodulating (minus nitrogen) and non-nodulating (plus nitrogen) conditions will also be determined.

Controlled hybridisation between elite trees of the three provenances will be determined by plant breeding scientists and will also include interspecific crosses between A. auriculiformis x A. mangium to develop new hybrid genotypes.