One look at the destruction of canola crops with the Brassica sylvestris gene on South Australia's Eyre Peninsula last year serves as a stern warning to Western Australia's canola growers.

The speed of that resistance breakdown suggests farmers in other areas will likewise receive little warning in the year before the breakdown occurs.

In the eastern states, the breakdown has already cost canola growers more than $20 million.

To reduce the chance of repeating such sudden failure of disease resistance, the Grains Research and Development Corporation (GRDC) has funded projects to prolong and improve blackleg resistance in canola varieties.

Species closely related to canola are being screened for blackleg resistance, with the aim of incorporating new blackleg resistance genes into canola. The first experimental lines will be tested in advanced yield sites this year.

A separate project this year will investigate the effect of rotating canola varieties with different types of resistance to the blackleg fungus. These studies aim to develop management strategies to protect and prolong varietal resistance to blackleg.

The third project, at the University of Western Australia, aims to identify improved resistance to blackleg, assess effective means of stubble removal and decomposition and reduce spore production on crop residues.

But what are the chances of the Eyre Peninsula-style breakdown occurring in WA?

A GRDC-funded 2003 survey by the Department of Agriculture evaluated 64 canola samples from Geraldton to Esperance, of which 68 per cent were Surpass 501TT and 11 per cent Pinnacle.

Found in all but one sample, blackleg affected an average of 64 per cent of the plants, with an average of 34 per cent of the crown circumference of each plant girdled by cankers.

The Department's Ravjit Khangura said a single major gene controls resistance in varieties derived from B. sylvestris . However, if a particular strain of pathogen is unrecognised by the resistance derived from B. sylvestris the plant does not respond to the fungus, resulting in the plant being particularly susceptible.

“The survey found the incidence and severity of blackleg in varieties with B. sylvestris genes almost doubled in 2003.

“This was predicted after strains with the ability to attack them were found in Western Australia and the eastern states,” Dr Khangura said.

The speed of blackleg fungus spread on the Eyre Peninsula in 2003 suggests stubble of infected plants will host resistant strains of the fungus during summer.

Other canola producing regions will likely experience similar level of disease in future years if varieties containing B. sylvestris resistance genes continue to be widely grown.