New wheat leaf rust menace

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Researchers have detected a new leaf rust pathotype on samples of the NaparooPBR logo wheat variety collected in northern New South Wales in early August.

Professor Robert Park identified the pathotype at the GRDC-funded Australian Cereal Rust Control Program based at the University of Sydney’s Plant Breeding Institute (PBI).

As a consequence of the discovery, Professor Park has urged grain growers to be vigilant in checking their crops for leaf rust, and submit plant samples they suspect are infected with the disease for testing.

He says the new pathotype found near Gragin and Graman, east of Moree, is a mutation of an existing pathotype that has added virulence for the leaf rust resistance gene, Lr24.

“This is the second mutation with virulence for the Lr24 resistance gene in Australia, and the first pathotype in Australia to combine this virulence with virulence for Lr13, Lr24 and Lr37 rust resistance genes,” Professor Park says.

“The parent pathotype that gave rise to this new mutant is exotic and was first detected at Inverleigh, Victoria, in late 2006.

“It has since become widespread in Victoria, southern and northern NSW, South Australia and Tasmania, providing an indication of the rate the new pathotype could spread its range,” he says.

Researchers are now testing wheat varieties with a a combination of either Lr13 and Lr24, Lr24 and Lr37, or all three genes to determine how they are affected by the new pathotype. These wheat cultivars include Carinya, EGA Jaegar, EspadaPBR logo, GBA Combat, GilesPBR logo, MerindaPBR logo, NaparooPBR logo, PetriePBR logo, QALBis, QAL2000 and Sunvex.

“Farmer who are growing any of these seven cultivars should monitor crops closely for leaf rust, and forward plant samples thought to be infected to the university’s PBI for pathotype analysis.”

He says testing so far has shown that these varieties, containing either Lr13 and Lr24, Lr24 and Lr37, or all three genes, are susceptible to the mutant pathotype at the seedling stage. However, further field tests of adult plants and greenhouse tests of seedlings are required to gauge the full impact of the new pathotype.

More information:

Professor Robert Park, 02 9351 8806, robert.park@sydney.edu.au

To send leaf rust samples to PBI for pathotype analysis, use paper envelopes (not plastic) and mail to:

Australian Cereal Rust Survey,
Plant Breeding Institute,
Private Bag 4011,
Narellan,
NSW 2567

Include the location, date and variety for samples, plus your contact information.

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