Genetics to help beat wheat disease

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Genome sequencing of the pathogen that causes the wheat disease tan or yellow spot is expected to accelerate the release of more resistant varieties and improve resistance ratings for existing cultivars.

The genome sequence for the pathogen, Pyrenophora tritici-repentis (PTR), was recently identified as part of collaborative research conducted by scientists from the US and Australia.

The director of the Perth-based Australian Centre for Necrotrophic Fungal Pathogens (ACNFP), Professor Richard Oliver, says estimates that the disease causes annual losses of more than $200 million in Australian cropping might be conservative.

“Research by Kalyx and the ACNFP in 2009 and 2010 suggests the disease causes yield losses between 0.3 and 0.6 tonnes per hectare, so the figure of $200 million may well be an underestimate,” Professor Oliver says.

Photo of woman inspecting plant

ACNFP tan spot researcher
Dr Caroline Moffat examines wheat
for tan or yellow spot disease at
WA’s Curtin University.

He says increased knowledge of the fungal disease through the PTR genome sequence is set to help researchers make new discoveries in tan spot virulence.

“In recent years, we’ve had access to some sequence data, which has already allowed us to breed improved varieties, but the pathogen has multiple weapons and the genome sequence is the key to finding and countering their effects.

He says ACNFP-led research examining the tan spot gene ToxA in 2006 has already helped to pinpoint the cause of losses resulting from the fungal disease.

“Since the discovery of the gene, the area planted to varieties that are insensitive to the ToxA gene has increased by about 25 per cent.”

He says breeders are also using their knowledge of ToxA to produce new varieties that have tan-spot-resistance levels equivalent to the MagentaPBR logo wheat variety. 

Sequencing of the tan spot genome follows both the cloning and sequencing of the gene for tan spot necrosis (Tsn1). This gene makes a protein in susceptible wheat varieties that helps tan spot and septoria (Stagonospora nodorum) infect leaves.

Professor Oliver estimates that sequencing of ToxA and Tsn1 could reduce Australian crop losses resulting from tan spot by about $100 million, and the PTR genome sequence could further halve these losses.

Leader of tan spot research at ACNFP Dr Caroline Moffat says the new genome sequence means her team can focus on finding sequences for Australian isolates of the disease and genetic analysis of Australian wheat varieties.

Dr Moffat says collaborative research has also identified other regions of the wheat genome associated with tan spot resistance. This work involves researchers from the ACNFP, the Department of Agriculture and Food, Western Australia, the Australian Centre for Plant Functional Genomics, the University of Adelaide, CSIRO and Australian wheat breeders.

“We are in the process of generating markers that breeders can use to accelerate the release of even more resistant varieties,” she says.

More information:

Professor Richard Oliver
0414 305 999
richard.oliver@curtin.edu.au

Dr Caroline Moffat
caroline.moffat@curtin.edu.au

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