Cereal rust corner with Dr Robert R Park and Dr Colin Wellings, University of Sydney (Dr Wellings is seconded from NSW Agriculture): Rust immigrants challenge resistance breeding

The recent foot-and-mouth outbreak in the United Kingdom serves as a graphic and timely reminder of the damage diseases can cause in agricultural production.

Australian agriculture is largely isolated from other regions of the world and, through stringent quarantine practices, it has been possible to keep out some agricultural diseases, particularly those that are soil-borne and tend to remain localised.

But what about wind-borne cereal rust diseases?

Annual monitoring of the rust pathogens of wheat over the past 70 to 80 years has provided a detailed I picture of the movement of rust diseases within Australia, and has also indicated periodic introductions of pathotypes from other parts of the world.

New pathotypes of the wheat stem rust pathogen were detected in 1925,1954 and 1969. More recently, new pathotypes of the leaf rust pathogen of wheat were detected; two in 1984, one in 1994, and one in 1998. The first appearance of stripe rust in Victoria in 1979 is yet another example.

Aerial transport of spores

Just how these new rusts reached Australia is in most cases unknown. Two stem rust pathotypes detected in 1969 are believed to have originated from central Africa, and it is thought that they reached Australia by aerial transport of spores across the Indian Ocean.

Studies of the stripe rust pathogen indicated that its spores can remain viable on clothing for up to seven days, and the evidence suggests that it was inadvertently introduced into Australia from southern Europe by contamination of travellers’ clothing. Interestingly, although this pathotype spread quickly through eastern Australia and to New Zealand, it has not managed to spread to the western wheat-growing regions.

The wind-borne nature of rust spores means that they can spread quickly, and experiences over thepast 70-80 years indicate clearly that we experience periodic introductions of rust isolates from other parts of the world.

Continued vigilance in quarantine is therefore vital. This is particularly so for two cereal rust diseases, stripe rust of barley and leaf rust of durum wheat, as these two diseases are not present in Australia. Future Cereal Rust Corner articles will address these two exotic cereal rust diseases, which pose potential problems for the Australian cereals industry.