It's a knock out for yellow spot
GroundCover™ Issue: 112 | Author: Melissa Williams
A world-first molecular breakthrough by Western Australian researchers is advancing efforts to breed wheat for resistance to yellow spot (also known as tan spot).
Infection levels of this costly disease were particularly high and widespread in WA’s medium and high-rainfall zones early this winter on the back of conducive seasonal conditions, increases in continuous wheat rotations and retention of high stubble loads from 2013 (yellow spot is stubble-borne).
In an attempt to cut losses from yellow spot, the GRDC and Curtin University’s Centre for Crop and Disease Management (CCDM) started a national ‘Stop the Spot’ campaign this year calling for growers to send in suspect wheat crop leaves for disease testing.
CCDM project leader Dr Caroline Moffat has been investigating yellow spot and its causes for the past five years.
She says the ‘Stop the Spot’ campaign will contribute to the development of an early detection system for increases in the virulence of the yellow spot fungus and its pathogenicity mechanisms.
In the laboratory, she and her CCDM team have achieved a world-first gene deletion – or gene ‘knock out’ – in an Australian strain of the yellow spot pathogen, Pyrenophora tritici-repentis (PTR).
This GRDC-funded research has seen the ToxA gene eliminated from this strain and replaced with a marker gene.
“The ToxA gene is the major effector – or toxin – of the yellow spot pathogen,” Dr Moffat says.
“It is secreted by the fungus and kills wheat cells, enabling the pathogen to colonise the crop.
“It only affects wheat varieties that are sensitive to this protein – which are those containing the tan spot necrosis 1 (Tsn1) susceptibility gene.
“This includes about two-thirds of the current commercial varieties used in WA [and nationally], including Yitpi and Stiletto.”
Dr Moffat says the gene-deletion method developed at the CCDM for ToxA was another step towards breeding for yellow spot resistance in wheat.
“Removing the extensive ToxA-induced necrosis now enables us to uncover other effectors of the yellow spot pathogen that have so far been masked by ToxA,” she says.
Dr Moffat says finding another one or two major effectors and developing simple tests for these would significantly boost breeders’ efforts to produce yellow-spot-resistant wheat varieties.
She says the gene-deletion method could also be used to target other genes of interest encoding additional effectors.
Dr Caroline Moffat,
08 9266 9186,
GRDC/Curtin University ‘Stop the Spot’ campaign: www.stopthespot.com.au
Dr Caroline Moffat’s full paper in Molecular Plant Pathology: http://onlinelibrary.wiley.com/doi/10.1111/mpp.12154/abstract
A fact sheet on Yellow Spot is available at: www.grdc.com.au/GRDC-FS-YellowSpotWest
GRDC Project Code CUR00023