An important new tool in the fight against fungus diseases in plants has been developed in Western Australia.

This tool, which is itself a fungus and has been called Sterile Red Fungus (SRF), was first isolated by Majeed Dewan, a PhD student at the University of Western Australia, on the roots of wheat plants from a farm in W.A.

It was found that wheat plants on which SRF was growing were immune to a devastating wheat disease called Take-all, Graminis var. tritici, usually abbreviated to Ggt. It has been estimated that Ggt can cost Australia up to $400 million each year in lost wheat yield.

Because SRF could not be induced to form spores or fruiting bodies, from which the classification of a fungus is determined, it has not been possible to classify and assign a species name to this strange organism.

Mr. Dewan was working with Dr K. Sivasithamparam's group in the Department of Soil Science and Plant Nutrition at the time; the group has been researching Take-all for many years. It was found that, not only did SRF immunise wheat against Take-all, it also made it grow larger, faster, and stronger.

The group also researched the effects of SRF on other plants, including cereals, legumes, and oil seeds. It was found both to be a successful colonizer of virtually all plants tested, and to have a beneficial and protective effect against other fungal diseases including Phytophthora (Jarrah dieback disease) and Rhizoctonia (Bare patch disease).

Following these discoveries, the research group formed an association with a local company, Biotech International Ltd., to exploit the new approach. Biotech have now developed a patented a new inoculum delivery system based on perlite, a porous mineral commonly used in horticulture.

Peter Keating, Director of Research and Development at Biotech, envisages a growing success with SRF in the fight against fungus diseases in plants. He also sees a much greater role for SRF in the future, based on genetic engineering principles.

Many plants could conceivably be improved along particular directions by genetic engineering, but their genes are relatively complex and difficult to manipulate. Fungi are genetically much simpler and readily amenable to genetic manipulation through techniques such as use of recombinant DNA.

In an article in "Australian Natural History" (Autumn 1991), Keating suggests that because SRF readily colonizes most plants, a genetically-engineered form of SRF (say one producing a natural insecticide) could give the same benefit as genetically working on the target plant itself.

Moreover, because fungi grow clonally like bacteria, large amounts can be produced relatively quickly, and applied to a range of plants (instead of needing to repeat the genetic engineering on each species).

What about that bogey of all genetic engineering work, that the product will somehow mutate into a monster and take over the world? Fortunately, as SRF is sterile, it cannot form spores to spread away from where it is deliberately introduced. And it can survive for only a short time in soil, so if its host plant dies, it rapidly declines.

It almost seems too good to be true. But the approach feels right - it is working with nature, using nature's own resources instead of synthetic chemicals to achieve a result. In the long run, such an approach will always be superior.

Ian Wood
New Scientist, 24 March 1990

DATE: January 1992

* * * * * * * * * * * * *