South coast growers are encouraged to check their barley crops for leaf rust symptoms following the detection of a new pathotype on the moderately resistant variety Bass in Western Australia.
This new pathotype of the barley leaf rust pathogen is the first occurrence of virulence for the Rph3 resistance gene in WA.
Department of Agriculture and Food (DAFWA) plant pathologist Kithsiri Jayasena said evidence pointed to the new pathotype arising as a mutation from the current strain of barley leaf rust, which has been prevalent on the south coast again this year following a wet spring.
“Seven samples of leaf rust from barley crops in Boxwood Hill, South Stirling, Chillinup and Kamballup were collected in mid-September and sent for analysis to the Australian Cereal Rust Control Program’s (ACRCP) laboratories at the University of Sydney,” Dr Jayasena said.
“These samples were collected from Bass barley and identified as pathotype 5457 P-, which has not previously been recorded.”
Dr Jayasena advised barley growers in leaf rust prone areas such as the South Coast to be aware that future plantings of Bass would likely require careful management of leaf rust, comparable to existing susceptible varieties.
Dr Jayasena said the 5457 P- mutation could also affect a number of other varieties carrying the Rph3 resistance gene.
Further monitoring and testing is underway by DAFWA and the ACRCP to assess the potential impact on Bass and other varieties including Fairview, Finniss, Fitzroy, Grange, Henley, Oxford, Wimmera and Yarra.
The leaf rust response of three of these cultivars (Grange, Henley, and Oxford) is not expected to change markedly due to the additional presence of the adult plant resistance gene Rph20.
“Growers of any of the potentially impacted cultivars should monitor their crops closely and forward samples of any leaf rust detected to the Australian Cereal Rust Survey shown below for pathotype analysis and contact DAFWA,” Dr Jayasena said.
Early detection and awareness of pathotype virulence against current resistant cereal varieties enables the grains industry to co-ordinate management and research to the most needed areas.
“Growers in leaf rust prone areas should be extra vigilant about controlling volunteer barley regrowth of any variety in the lead-up to 2014 crop plantings, especially if there is a wet summer,” Dr Jayasena said.
The ACRCP monitors rust pathogens around Australia to highlight rust pathogen changes that represent risks to Australian cereal producers.
Dr Jayasena said this early detection of Rph3 virulent leaf rust highlighted the value of the collaborative work being done by DAFWA and ACRCP with the support of the Grains Research and Development Corporation (GRDC) for national rust detection and control.
“Through the ACRCP initiative, the identification of varieties that may become fully susceptible in the presence of the new pathotype allows for leaf rust management strategies to be adjusted by both growers and breeders,” Dr Jayasena said.
Rusted plant samples can also be mailed in paper envelopes, do not use plastic wrapping or plastic lined packages to: Australian Cereal Rust Survey, Private Bag 4011, Narellan NSW 2567.
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