Sequence to slash losses from worst wheat disease

Date: 13 Nov 2012

Lady looks at long green crops

Genome sequencing of the wheat disease tan (yellow) spot pathogen is expected to help researchers boost the productivity of the Australian wheat industry by tens of millions of dollars in coming years.

The genome sequence for Pyrenophora tritici-repentis (PTR) was published recently by United States and Australian researchers, following collaborative research between the countries.

According to the Australian Centre for Necrotrophic Pathogens (ACNFP), which is supported by the Grains Research and Development Corporation (GRDC), it will accelerate the release of more resistant Australian cultivars and improve resistance ratings for existing varieties.

ACNFP director Richard Oliver said tan spot was the most costly disease affecting Australian and Western Australian cropping, and was estimated to cause national annual losses of more than $200 million. 

“Research carried out by Kalyx and the ACNFP in 2009 and 2010 suggested that wherever the disease is present, it causes yield losses of 0.3 to 0.6 tonnes per hectare, so $200 million may well be an underestimate,” Professor Oliver said.

He said having access to the full genome sequence for PTR, the cause of tan spot, revolutionised Australian researchers’ knowledge of the fungal disease by giving them access to previously unknown tan spot virulence factors. 

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

“Data relating to the tan spot gene ToxA - generated independently by an ACNFP-led consortium in 2006 - has also already pinpointed the cause of much of the yield losses caused by tan spot.

“The area planted to ToxA insensitive varieties in WA has increased by about 25 per cent since the discovery of the gene.

“Breeders are also using tools relating to ToxA to produce new varieties with resistance levels at least as good as MagentaPBR logo, which has the best resistance levels of current commercially available varieties.”

Professor Oliver said the sequencing of the tan spot genome also followed the 2010 cloning and sequencing of the gene for tan spot necrosis 1 (Tsn1) – the protein produced by susceptible wheat cultivars, which helped tan spot and septoria (Stagonospora nodorum) infect the leaves.

“Based on data in the 2009 GRDC report The current and potential costs of diseases of wheat in Australia, I estimate that the sequencing of ToxA and Tsn1 will ultimately cut Australian crop losses caused by tan spot by about $100 million, while the PTR genome sequence should at least halve losses again,” he said.

Caroline Moffat, who leads ACNFP research into tan spot, said her team was following up the US research – led by Oregon State University – by developing sequences of Australian isolates of the tan spot pathogen and genetic analysis of Australian wheat cultivars.

“Our collaboration with the Department of Agriculture and Food (DAFWA), the Australian Centre for Plant Functional Genomics (ACPFG), University of Adelaide, CSIRO and Australian wheat breeders has identified several other wheat genome regions associated with tan spot resistance,” Dr Moffat said.

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


PHOTO CAPTION: ACNFP tan spot researcher Caroline Moffat examines wheat at Curtin University, WA. (click image above to download high resolution version)

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GRDC Project code: CUR0012