IUFRO Breeding theory and progeny testing

At the IUFRO Conference “Eucalyptus in a Changing World” in Aveiro, Portugal, in October 2004, I was struck by a remark made in one of the sessions to the effect that little work on eucalypt breeding seems to be going on in Asian countries. While some of the work is under-reported in the international literature, many Asian countries in fact have well-advanced programs of domestication and genetic improvement for eucalypt species and other tree genera of Australian origin.

Australian tree genera are very prominent in tropical and subtropical plantation forestry (Evans and Turnbull 2004). In addition to their use in formal plantations, eucalypts and other Australian species are planted widely in rows or as individual trees on farms, around homesteads, and along canals and roadsides throughout much of the warmer regions of the world. Plantations of Acacia species of Australian origin are estimated to occupy about 2 M hectares, and continue to expand rapidly (Midgley and Turnbull 2003). Planting of Australian species as exotics began in the late 18th century, and has continued at an accelerating rate, despite some controversies over issues such as weediness, water use, social impacts and land ownership.

Commencing in the 1960s, with the support of FAO and IUFRO, international species and provenance trials based largely on seed collections made by CSIRO’s Australian Tree Seed centre were established in many countries. The most productive species and provenances of Eucalyptus and Acacia, and other Australian genera prominent in tropical plantation forestry such as Casuarina, Grevillea and Melaleuca were identified. Important new plantation species such as A. crassicarpa were “discovered” and domesticated in this process. Over the past twenty years, A. crassicarpa has gone from a virtually unknown tree in the wilds of north Queensland and New Guinea to a major commercial plantation species for pulp and paper in Southeast Asia (Midgley and Turnbull 2003). China, Indonesia, Thailand and Vietnam all now have well-established progeny testing programs and seed orchards for this species.

Inbreeding and negative selection, often from a sub-optimal initial introduction, have caused severe genetic deterioration in many unmanaged land races of key Australian tree species, with resulting declines in the productivity of plantations based on informally collected seed (Harwood et al. 2004). Over the 1980s and 1990s, strong efforts were made to establish in-country mass-production of genetically improved planting stock based on superior provenances of key species, through seed orchards and clonal programs. Government research agencies and some private companies in many Asian countries now have well-established breeding populations based on appropriate provenances of their key species, and seed orchards and clonal programs delivering large quantities of improved planting stock, resulting in substantial gains in plantation productivity. A recent meeting in Bangkok, Thailand, sponsored by the Australian Centre for International Agricultural Research (ACIAR) and attended by lead scientists from national agencies charged with forest genetic research, documented the domestication status of Australian species in Asian countries. This information is summarised in Table 1 below.

Eucalyptus and Acacia breeding programs in some Asian countries.

It can be seen that countries such as China, India, Indonesia, Thailand and Vietnam are well-advanced in overall domestication of Australian species.  Forest plantation companies have now established sophisticated tree improvement programs to support large scale industrial plantings – Acacia mangium, A. crassicarpa and E. pellita in Indonesia and the programs to develop hybrid eucalypt clones in China are good examples. Genetically improved planting stock (relative to the best wild introductions) comprises a rapidly growing percentage of new plantations.  In southern India, for example, seedling seed orchards established in the mid 1990s (Varghese et al. 2000) already provide about 20 kg of improved E. camaldulensis and E. tereticornis seed per year, sufficient to establish more than 2,000 ha of plantations.  The breeding populations of these species established in southern India have also yielded a new series of highly productive clones for clonal forestry, and form a genetic base for hybrid breeding. Growth of the orchard seed in genetic gain trials is superior to that of local commercial seed sources (Mohan Varghese, pers. comm. 2004).

In China, which now has over 1.5 M hectares of eucalypt plantations, new plantings are delivering yields of around 20 m3 ha-1 year-1, almost three times that achieved with previously-used species and silviculture (Van Bueren 2004). The development of high-yielding trees has been at least partly responsible for the rapid expansion in planting area, and it was concluded that the eucalypt research and development supported by ACIAR and implemented by Chinese research institutes in partnership with Australian forest research agencies has almost certainly made a considerable contribution to improving the living standards of rural people in southern China. In Vietnam, the establishment of over 130,000 hectares of highly productive clonal plantations of the acacia hybrid A. mangium  x auriculiformis is an outstanding achievement, considering that research on tropical acacias commenced in that country only in the late 1980s (Le Dinh Kha 2001; van Bueren 2005, in press).

Acknowledgments

The Australian Government has supported a number of tree domestication projects via support from ACIAR and AusAID.

References

Evans, J. and Turnbull, J.W. (2004). Plantation Forestry in the Tropics. The role, silviculture and use of planted forests for industrial, social, environmental and agroforestry purposes. Oxford University Press.

Harwood, C., Ha Huy Thinh, Tran Ho Quang, Butcher P.A. and Williams E.R. (2004). The effect of inbreeding on the early growth of A. mangium in Vietnam. Silvae Genetica 53:65-69.

Le Dinh Kha (2001). Studies on the use of natural hybrids between Acacia mangium and Acacia auriculiformis in Vietnam. Agricultural Publishing House, Hanoi.

Midgley, S.J. and Turnbull, J.W. (2003). Domestication and use of Australian acacias: case studies of five important species. Australian Systematic Botany 16: 89-102.

Van Bueren, M. (2004). Eucalypt Tree Improvement in China. Impact Assessment Series Report No. 30. Australian Centre for International Agricultural Research, Canberra.

Van Bueren, M. (2005). Acacia hybrids in Vietnam. Impact Assessment of ACIAR-funded project FST/1986/030. Australian Centre for International Agricultural Research, Canberra (in press).

Varghese, M; Nicodemus, A; Nagarajan, B; Sasidharan, K.R; Siddappa; Bennet, S.S.R. and Subramanian, K. (2000). Seedling Seed Orchards for Breeding Tropical Trees. Institute of Forest Genetics and Tree Breeding, Coimbatore, India.

Contact: Chris Harwood, Ensis, Private Bag 12, Hobart 7001, Australia .