Cereal rust has damaged grain crops for centuries. Australian researchers have tracked three sources of new rust strains: mutation, somatic hybridisation, and exotic incursions, which arrived 13 times in 95 years. Regular rust surveys catch dangerous new variants before they spread.
Questions this video answers
1901.
1926.
1917 (studies continued annually since 1920).
1940s.
Mid-1950s.
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Cereal rust has been plaguing grain crops around the world for thousands of years. So it should come as no surprise that research into cereal rust pathogen variation is one of the Australian grains industry's longest running R and D programs. While aware of the huge impact of rust, early cereal breeders, including the father of the Australian wheat industry, William Farrer, tried tried to find solutions by working around rust. His most successful variety federation, released in 1901, was an early maturing, drought tolerant wheat. However, in 1926, a new rust strain, Race 126, spread across the country from WA and Federation's long run was over. Farra didn't live to see its demise or the start of a new era in rust pathogen analysis.
The University of Sydney became involved in that work way back in 1917, when Professor Wardhouse initiated studies on variability in rust pathogens. And that work on variability in rust pathogens has continued continually every year since 1920.
Waterhouse was a plant breeder and his research into rust pathogens raised the bar. Also, like Farrah, Waterhouse is remembered for a wheat variety Gabo, registered in the 1940s. It had good rust resistance, but by the 50s it had become susceptible to new strains of leaf and stem rust. It was a reminder of the ongoing need for rust analysis. The rust pathogen variation program was moved off the university's main campus.
In the mid-1950s, the plant breeding Institute was established at Castle Hill and the work transferred to there. And then in 1991 the plant breeding Institute relocated here to Cobbardy and the work has continued here ever since then.
The physical process by which rust strains or pathogens are identified hasn't changed much since 1920. Rust spores supplied by grain growers are applied to indicator genotypes, each with a different resistance gene. The pathogen's ability to infect the genotype determines its strain. Decades of rust analysis mean much has been learnt about pathogen variation.
So over the past 95 years in Australia, with the wheat rust pathogens, we know that there's no sexual recombination occurring, that they are in essence clonally reproducing organisms, that the variation comes from one of either three sources.
The most common source is mutation. Another is somatic hybridisation, where genetic properties of different rust pathogens fuse together to form a new strain. But that's quite rare. The most dangerous source is exotic incursion. In the past 95 years, it's happened 13 times.
We can tell it's come from overseas because it's so different to what we have. And those new isolates that come in from overseas can have a huge impact on the wheat varieties that we're growing. I think many viewers would remember the situation in the early 2000s, when we had a new incursion of striped rust that we call the WA pathetype that affected many, many different wheat varieties. And we believe that probably, most probably came from North America.
And the frequency with which these exotic incursions are occurring is increasing.
Two years ago, we had an incursion of leaf rust from overseas. We don't know where it came from again, but it turned up in South Australia. Within 12 months, that isolate was present in, in all wheat growing parts of Australia, including Western Australia. So that's a very graphic example of how quickly these things can move around once they get in.
But by growers participating in the rust surveys, their samples can be analysed, the rust strain identified, and reliable predictions made about a variety's continued resistance to rust. Knowledge vital to cereal pre breeding programs.
So that pre emptive breeding strategy, where we can actually guess what the pathogen is going to do next quite accurately and then breed accordingly, is a very, very important strategy in controlling rust with genetics. And our ability to do that is essentially based on all of the information that comes from the surveys.
Rust has been impacting global cereal crops for 3,000 years. Yet in the past 95, the Australian grains industry's understanding of rust pathogen variation has come a long way. A major contribution to that understanding is the continued support of the serial rust survey. To find out what happens when surveys are not well supported, go to the final part of this report.
