New wheat leaf rust pathotype detected in Western Australia

Several wheat varieties, including widely grown Wyalkatchem, are likely to have their disease resistance rating for leaf rust shifted towards greater susceptibility following the detection of a new leaf rust pathotype in Western Australia.

This new pathotype was recently found at both ends of the Wheatbelt and is the first occurrence of virulence for the resistance genes Lr13, Lr17a, Lr17b, and Lr26 in WA.

Department of Agriculture and Food plant pathologist Ciara Beard said five samples of leaf rust from wheat crops around Northampton, Borden and Esperance were identified as being the new pathotype by the Australian Cereal Rust Control Program’s (ACRCP) laboratories at the University of Sydney.

“These samples were collected from a range of varieties showing unusually high levels of leaf rust, including Wyalkatchem which was previously regarded as RMR (resistant – moderately resistant) to leaf rust in WA,” she said.

Ms Beard said the new pathotype was first detected in eastern Australia in 2011 and is presumed to have entered WA on prevailing winds or someone’s clothing.

“While the pathogen is unlikely to have any impact on this year’s crops, it serves as a management warning for growers for next year, particularly if summer rain enables a green bridge to carry inoculum into next season,” she said.

Subject to further testing by the ACRCP, the presence of the new leaf rust pathotype is expected to result in Emu Rock’s leaf rust rating being revised down to MSS (moderately susceptible – susceptible) and Wyalkatchem and Corack to MS (moderately susceptible).

Some varieties such as King Rock, Fortune and Zippy have leaf rust genes that are expected to still be effective and will have a lesser rating shift to MRMS (moderately resistant – moderately susceptible).

Cultivars Mace, Carnamah and Cobra could also be vulnerable to the new pathotype but further tests are needed to establish their responses more accurately.

Further monitoring and testing is underway by the ACRCP to confirm the potential impact on WA wheat varieties.

Ms Beard advised wheat growers in leaf rust prone areas, including those where leaf rust has been found this season, to destroy any volunteer wheat regrowth before the 2014 season and to carefully consider management of these affected varieties.

She said the detection highlighted the value of national rust detection and control work by DAFWA and ACRCP with the support of the Grains Research and Development Corporation (GRDC).

She also acknowledged the work of growers and consultants who identified and submitted the leaf rust samples.

“Early detection and awareness of pathotype virulence against current resistant cereal varieties is important in allowing the grains industry to co-ordinate disease management, research and work on new breeding lines,” she said.

“Growers and agronomists are encouraged to report any further discoveries of leaf rust on late maturing crops to DAFWA and submit samples to the Australian Cereal Rust Survey for pathotype analysis.”

Samples can be mailed in paper envelopes, not plastic wrapping or plastic lined packages, to: Australian Cereal Rust Survey, Private Bag 4011, Narellan NSW 2567.