An eastern Australian wheat leaf rust (Puccinia triticina) pathotype has been identified in Western Australia, which may cause the rust resistance ratings of several wheat varieties to change.

Varieties that may become more susceptible to leaf rust include Mace, which is the most popular wheat variety in WA.

Wheat leaf rust can significantly reduce wheat yields on susceptible varieties, given appropriate environmental conditions.

Growers are advised to make careful variety selections and to be aware of the resistance ranking of their chosen varieties for 2016.

The wheat leaf rust pathotype new to WA was submitted to the Grains Research and Development Corporation (GRDC)-supported Australian Cereal Rust Control Program (ACRCP) at the University of Sydney, where it was identified by Professor Robert Park.

He said the pathotype 104-1,3,4,6,7,8,10,12 +Lr37 was identified in samples of leaf rusted wheat collected from four separate locations in the northern region of the WA grainbelt in late September.

“This pathotype was first detected in South Australia in August 2014, and has since spread throughout much of the eastern Australian grainbelt, and now to WA,” Professor Park said.

“This is only the third example of a wheat rust isolate migrating from eastern Australia to WA in the past 25 years, all being wheat leaf rust, but it is concerning that two of these incursions have occurred in the last two years.”

Professor Park said the pathotype’s impact on wheat varieties grown in WA would be better understood at the end of this year, after the completion of field testing.

“In the meantime, the cultivars Arrino, Binnu, Emu Rock, Envoy, Estoc, Grenade CL Plus, Mace, Tammarin Rock, and Zippy should be monitored closely for leaf rust,” he said.

“If rust is detected in these varieties, growers are encouraged to send samples of leaf rust to the University of Sydney Plant Breeding Institute for pathotype analysis.”

Rusted plant samples can be mailed in paper envelopes (not plastic wrapping or plastic-lined packages) to the University of Sydney, Australian Cereal Rust Survey, Reply Paid 88076, Narellan, NSW, 2567.

Department of Agriculture and Food (DAFWA) plant pathologist Geoff Thomas said the incursion of the pathotype was concerning, particularly following the 2013 identification of the separate 76-1,3,5,7,9,10,12 +Lr37 pathotype, which had resulted in resistance ratings of varieties including Mace being reclassified.

“Changes in variety classifications highlight the impact of rust incursions and demonstrate the importance of continued vigilance to stop the introduction of pathotypes, and monitoring for early identification of incursions,” he said.

“While it is not known how the wheat leaf rust pathotypes entered WA from the eastern states, people should take precautions when travelling between farms, because rust can be introduced to new locations via clothing and footwear.

“To minimise the risk of crop damage from rust next season, WA growers need to think carefully about the varieties they plan to retain or source for crop seed.

“Controlling the ‘green bridge’ and monitoring summer-autumn regrowth is imperative to limit carryover of rust into the 2016 growing season.”

Information on developing a rust management strategy can be found on the Rust Bust website www.rustbust.com.au, which includes a ‘Rust Bust Management Checklist’.

The ACRCP is one of the GRDC’s core investments to monitor, assess and develop a rust management strategy for Australian growers.