Close eye on new wheat stripe rust

It is too early to know which popular wheat varieties will be most susceptible to a new wheat stripe rust pathogen found in eastern Australia, currently being assessed by Sydney University's Plant Breeding Institute.

Tests carried out late last year on samples from southern NSW and Wimmera in Victoria at the Institute confirmed the presence of a new pathotype of the fungus which causes wheat stripe rust.

NSW Department of Primary Industries Principal Research Scientist, Dr Colin Wellings, told a Rust Diseases symposium in Sydney this week that the big concern about the new pathotype is that it is virulent against the Yr17 resistance gene.

Wheats now under question include Carinya, Ellison, Barham, Braewood, Derrimut, Marombi, Pugsley, Rudd, Sunbri, Sunlin, Sunstate, Sunvale, Sunzell, Ventura and Young. Varieties QAL2000, Camm and H46 are expected to be susceptible to this new pathotype.

The Yr17 gene had provided NSW growers with protection against the WA pathotype that emerged in Western Australia in 2002, causing widespread damage.

However, the susceptibility of Yr17 to this new pathotype means that a majority of commercial wheats grown in eastern Australia are potentially more vulnerable to the WA pathotype.

Dr Wellings said trials will be carried out this year in greenhouses and field plot nurseries.

The implications for specific varieties in 2007 will depend on the distribution of the new pathotype.

"This in turn will be governed by opportunities for summer survival and the re-emergence of the new pathotype in the new cropping season," Dr Wellings said.

He said all varieties with Yr17 should be considered vulnerable and will need to be carefully monitored during the growing season.

His estimate is that it could be two to three years before wheat varieties containing Yr17 are affected by the new pathotype.

"If this proves to be the case, then there should be time for farmers to change the varieties they are planting," Dr Wellings said.

"The remaining resistance genes Yr18, Yr27 and Yr33 are still effective against stripe rust."

The symposium, organised by the NSW Centre for Animal and Plant Biosecurity, is on the topic - "Rust Diseases: Threats to Global Food Security in the Context of Climate Change."

Today's speakers examined cereal rusts, including international concerns about a new virulent rust known as Ug99 which has emerged in Africa and jumped to Yemen in the Arabian peninsula.

Tomorrow, speakers will examine exotic rusts in forestry, the use of rust pathogens as weed biological control agents, and possible impacts of climate change on rusts.