In August 2014 leaf rust was identified in Revenue wheat, previously rated resistant (R), in south east South Australia. The September issue of Crop Watch (465kb PDF) reported several crops in South East SA and one crop near Gawler appeared to be infected with the new strain of wheat leaf rust.
Following testing at the Plant Breeding Institute (PBI) at The University of Sydney it was confirmed that the strain was an exotic wheat leaf rust pathotype. The results of this testing were published in Issue 3 of the PBI’s Cereal Rust Report (606 kb PDF).
The new pathotype exhibits virulence for three rust resistance genes in wheat – the complementary genes Lr27+Lr31, Lr15 and Lr28. This new pathotype is expected to spread widely throughout the eastern states from the first point of detection in SA. Growers and advisors are advised to monitor crops closely next season and forward samples to PBI for analysis (Dispatch form 29kb PDF). Seedling and adult plant tests, both in the glasshouse and the field are being undertaken to understand the full impact of the new pathotype.
The October Cereal Rust Report (272kb PDF) identified at least trace amounts of the new pathotype in all samples received from SA. The new strain was determined to be sufficiently different from all previous samples and classified ‘exotic’. The strain was most likely present in 2013 and previous years, however at low levels and therefore remained undetected.
Although not endorsed through the NVT rating process, SARDI released provisional changes to resistance ratings in the November 2014 Crop Watch, detailed below.
Check the updated Cereal Variety Diseases Guides for the final version of the new rust ratings.
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In particular, in 2015 a large area of SA will now be sown to susceptible varieties. This makes it all the more important to protect these varieties in future years if wheat is present over summer.
- SARDI Crop Watch Newsletters
- Australian Cereal Rust Control Program Reports and Forms including all Cereal Rust Reports and forms (29kb PDF) for submitting samples to the Plant Breeding Institute.
- Now is the time for monitoring – GRDC article with information about when to monitor and the importance of monitoring for cereal rust pathogens.