September 10,  2001

Scientists are 'pyramiding' several different pest resistance genes to help win the war against
parasitic worms in wheat.

CSIRO Plant Industry scientist Dr Evans Lagudah says the multi-pronged protection against Cereal Cyst Nematode (CCN) is reducing a $70 million per year cost to the wheat industry.

CCN is a parasitic worm that attacks and then multiplies on the roots of susceptible cereals.

Infested plant root systems become gnarled balls, which inhibit plant growth and dramatically
reduce yield. Resistant plants stop the nematode from reproducing in plant roots.

"Several different lines of defence are always more effective than one," says Dr Lagudah.

"Like all parasites, CCN can change to overcome the single line of defence provided by just one
resistance gene.

"By 'pyramiding' a number of different resistance genes in one plant we can reduce the risk of
new virulent strains of nematode emerging," he says.

"So far we have found five CCN resistance genes from wild relatives of bread wheat from West
and Central Asia. Using conventional breeding methods, the resistance from the wild relatives
has been crossed into Australia's most advanced wheat breeding lines."

In the past, adding the resistance trait from wild wheat has in some cases resulted in a sacrifice
of either grain yield, grain quality, or both.

Field trials have shown that the new resistant lines have performed well, with no impact on grain
quality.

To bring these promising results to farmers sooner, the scientific team combined conventional
breeding techniques with DNA technology using DNA markers enabling them to develop
nematode resistant crops faster.

"DNA markers act like signposts, enabling us to keep track of the resistance gene through the
cross-breeding process, so we know if resistance has also been passed on to the new generation
of plants," says Dr Lagudah.

"We have gone one step further to develop what is called a 'perfect' marker to track the
resistance gene with complete accuracy," he says.

"This is what makes the whole process faster. Because of the DNA marker, we can screen wheat
seedlings for CCN resistance in just a few hours, rather than the three months or more taken in
conventional breeding."

The CCN resistant wheat breeding lines have been widely tested by the Victorian Institute of
Dryland Agriculture in Australia, and by CIMMYT, the International Maize and Wheat
Improvement Centre, in Mexico.

The combined use of gene technology and conventional plant breeding to improve disease
resistance will also be extended to other cereal diseases, such as root lesion nematode and
crown rot.

This research is a collaborative effort between CSIRO Plant Industry and the Department of
Natural Resources and Environment initially supported by the Grains Research and Development
Corporation (GRDC). Graingene now funds this project.

Graingene is a strategic alliance involving three of Australia's leading agricultural organisations:
AWB Limited, CSIRO, and the Grains Research and Development Corporation (GRDC). Launched
in April 1999, Graingene aims to generate innovative intellectual property and new generation
plant biotechnology research for the grains industry.

More information from:
Dr Evans Lagudah, CSIRO Plant Industry, 02-6246 5392
Rachael Mitchell, CSIRO, 02-6246 5323, 0417 240 261

CSIRO news release
N3801