Australasian Plant Conservation

Originally published in Australasian Plant Conservation 17(1) June - July 2008, pp 30-31

Development of conservation technologies for Australia's rainforest and tropical native fruits

Kim Hamilton¹ and Sarah Ashmore^2
1Botanic Gardens Trust, Mount Annan Botanic Garden, NSW. Email: kim.hamilton@rbgsyd.nsw.gov.au
²Centre for Forestry & Horticultural Research, Griffith University, Brisbane.

Australia's Crop Wild Relatives 

Crop wild relatives are native taxa that are close relatives of commercial crop plants and represent the wider genetic diversity of the crop gene pool. They are a valuable source of functional traits (e.g. disease resistance, flood tolerance and medicinal properties) for improvement of food, forestry and medicines. Thus, continuing access to the existing crop wild diversity is important. Australia has crop wild relatives of many species economically important worldwide. Some of the nationally and internationally significant crop wild relatives and bush foods of Australia are listed in Table 1. They include rainforest genera that contain commercially cultivated species (e.g. Macadamia integrifolia), crop wild relatives of commercially important species (e.g. Macadamia spp., Citrus spp., Musa spp.) or bush foods of local importance (e.g. Citrus australasica, Finger Lime; Davidsonia pruriens, Davidson's Plum) (Fig. 1). Table 1 also provides a summary of the percentage of species under threat for their genus in Queensland. 

Vulnerability of Rainforests to Climate Change 

One of the key risks of projected climate change is its effect on Australian rainforests, which are one of five natural systems predicted to be vulnerable to damage (Hennessy et al. 2007). Climate change is predicted to interact with other threats, such as weeds and habitat fragmentation, in some of the most vulnerable environments including the Wet Tropics. For example, relative to 1990, about a 50% decrease in montane tropical rainforest area in northern Australia is predicted by 2020 (Hennessy et al. 2007). 

Figure 1. Rare and threatened rainforest crop wild relatives. Fruit (A) and seeds (B) of Davidson’s Plum (Davidsonia sp.). Fruit (C) and cut fruit (D) of Mount White Lime (Citrus garrawayi). Photos: N. Hall (A,B) and K. Hamilton (C,D)

Conservation of Rainforest Seeds 

The seed of many species can be routinely stored ex situ in seed banks using standard desiccation (5% moisture content) and freezing (-20°C) protocols; such species have 'orthodox' seeds. However, not all species are amenable to these procedures (i.e. they have 'non-orthodox' seeds) and require the development of alternative conservation technologies, particularly in vitro and approaches using very low temperatures (i.e. cryopreservation), before long-term ex situ conservation can be achieved (Pritchard 2004; Ashmore et al. 2007). Conservation of these species is thus currently restricted to in situ approaches or field collections ex situ, making them particularly vulnerable to loss. 

The number of Australian species with non-orthodox seeds is unknown. Recent studies have estimated that worldwide up to 30% of flowering plants or >80,000 species may have desiccation sensitive seeds and thus not be amenable to standard seed banking protocols. Tweddle et al. (2003) estimate that 48% of species in non-pioneer evergreen rainforest world-wide will have seeds that display desiccation sensitivity. 

Target 8 of the Global Strategy for Plant Conservation is to achieve "60 per cent of threatened plant species in accessible ex situ collections ." giving clear recognition for the importance of ex situ conservation to support in situ initiatives. Target 8 also states the need for "additional resources, technology development and transfer, especially for species with recalcitrant seeds" (i.e. non-orthodox seeds). Thus, there is an urgent need to develop technologies (e.g. cryopreservation, Fig. 2) to conserve the diversity of Australia's rainforest species. Many of the rare and threatened crop wild relative species in the genera listed in Table 1 are of rainforest and/or tropical origin with likely non-orthodox seeds. 

Case Study 

International and national partnerships have been established to develop alternative technologies for the conservation of Australian species with non-orthodox seeds. These include the Millennium Seed Bank Project (Royal Botanic Gardens Kew, UK), the Queensland Seeds for Life project and the Rainforest Seed project (Botanic Gardens Trust, Mount Annan, NSW).An example is the development of conservation technologies for the rare Citrus garrawayi (Mount White Lime), an edible lime with unique fruits (Fig. 1C, 1D) that grows in the monsoon forests and rainforests of Cape York Peninsula, Queensland. The ex situ storage and use of its seeds are hindered by seed availability (i.e. limited access and supply), quality (e.g. maturity) and some desiccation sensitivity. However seeds can be stored by cryopreservation and also be coupled to a straight forward in vitro propagation system (Hamilton et. al. 2008). This example illustrates the use of conservation technologies to create ex situ storage options and facilitate propagation for utilisation of plant material (e.g. for horticultural and restoration purposes). 

Table 1. Some Queensland genera with likely non-orthodox seed and of socio-economic importance as Crop Wild Relatives (CWR) or Bush Foods (BF)¹, with numbers and percentages of species in each genus under conservation threat².

¹Table modified from Ashmore et al. (2007)
²From Henderson (2002)

The Future 

There is growing recognition of the national and international importance of crop wild relatives as a vital source of genetic diversity, and of the increasing threat to these from habitat destruction and climate change. Thus there is an urgent need to develop alternative ex situ conservation technologies, especially for rainforest fruits and crop wild relatives which currently cannot be stored by standard seed banking methods. It is imperative to (i) develop secure conservation collections and (ii) develop conservation technologies such as cryopreservation for the ex situ conservation of non-orthodox seeded species. This will contribute to Australia's commitment to the Global Strategy for Plant Conservation and the International Treaty on Crop Genetic Resources. 

References 

Ashmore S.E., Hamilton K.N. and Pritchard H.W. (2007). Development of conservation biotechnologies in response to Target 8 of the GSPC. In: Proceedings of the Third Global Botanic Gardens Congress, Wuhan, China, April 2007, http://www.bgci.org/files/Wuhan/PapersConserving/Ashmore.pdf. 

Hamilton, K.N., Ashmore, S.E. and Drew, R.A. (2008). Desiccation and cryopreservation tolerance of near mature seeds of Citrus garrawayi. Seed Science and Technology 36: 157-61. 

Henderson, R.J.F. (Ed.) (2002). Names and Distribution of Queensland Plants, Algae and Lichens. Queensland Herbarium, Environmental Protection Agency, Brisbane. 

Hennessy, K., Fitzharris, B., Bates B.C., Harvey, N., Howden, S.M., Hughes, L., Salinger, J. and Warrick, R. (2007). Australia and New Zealand. In: M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson (eds). Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, pp. 507-40. Cambridge University Press, Cambridge, UK. 

Pritchard, H.W. (2004). Classification of seed storage types for ex situ conservation in relation to temperature and moisture. In: E.O. Guerrant Jr., K. Havens and M. Maunder (eds). Ex Situ Plant Conservation Supporting Species Survival in the Wild, pp. 139-161. Island Press, Washington DC, USUSA. 

Tweddle, J.C., Dickie, J.B., Baskin, C.C. and Baskin, J.M. (2003). Ecological aspects of seed desiccation sensitivity. Journal of Ecology 91: 294-304.

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