Australia has at least three species of 'native' or 'wild' , all within the same genus as domestic rice, sativa. These native species include O. meridionalis, O. australiensis and O. rufopogon. Oryza officinalis might also occur in the remote parts of Arnhem Land. Oryza meridionalis and O. rufipogon are genetically close to O. sativa while O. australiensis is phylogenetically remote. Hardly anything is known about the biology of these even though they are related to the most important food source on Earth.

Distribution

These species grow in an arc across monsoonal northern Australia, from south of Townsville to Broome. They encroach far inland where billabongs and waterways permit them to source a water supply during summer when they grow and reproduce. Thus some populations have been isolated for millennia and are genetically distinct. This makes them excellent tools for research.

Habit

These are all grasses with C3 photosynthetic pathways. Some grow in clumps that might be scarcely a metre tall while in wetter regions there are dense meadows (O. meridionalis). Individuals can be two or three metres tall (O. australiensis). Oryza australiensis is perennial, re-sprouting from a rhizome in the following wet season. Their long strap-like leaves eventually give way to a cluster of heads, each with a rachis bearing with long barbed awns. The florets, still with their awns attached, fall off after ripening and are exquisitely adapted to attach themselves to the coats of passing animals for dissemination.

Seeds

Seeds are about half the size of domestic rice and highly enriched in micronutrients and protein. They are therefore relatively low in starch. We know nothing about their other nutritional properties (vitamins, anti-oxidants etc) but in that they are darkly coloured, they seem to be rich in tannins when ripe. Aboriginal groups used them as a food source but they remain unexploited by modern .

Seeds of Oryza rufipogon

Our research:

There is a worldwide effort to improve rice yields, not least the Gates Foundation which is funding the search for a C4 rice with rapid photosynthesis like maize and sugar cane. This would be the Holy Grail of world food production but is a long shot. We take a more eco- physiological approach. These Australian rice species grow in extreme environments in the tropical savanna where temperatures are extreme when compared to SE Asia and monsoonal rainfall is inconsistent. This has probably conferred drought tolerance on these species. Some are daylength sensitive, others are not. Yet other ecotypes grow in salty marshland where rice could normally not grow. These variants are being used in a programme of identification of the mechanisms of stress tolerance and their incorporation into domestic rice. We are making progress with heat, drought and salt tolerance and will press on with discovery of novel accessions and important genes using physiological and molecular techniques. Ultimately, breeding programmes through our colleagues at the International Rice Research Institute and biotechnology with our industry partners will be used as a vehicle for improvement of this essential grass.

Department of Biological Sciences Macquarie University, NSW, 2109, Australia

Production: A. & K. Downing 17 September 2012 Map and photograph of seeds of Oryza rufipogon: Atlas of Living Australia, http://bie.ala.org.au/species/Oryza