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Stop the Spot continues the fight

Yellow spot causes tan - coloured lesions on the leaves that are surrounded by yellow halos.

Yellow spot causes tan – coloured lesions on the leaves that are surrounded by yellow halos.

Growers and advisers are being encouraged to send in samples of leaves with yellow spot and join researchers in the fight against yellow spot.

Results from the second year of the Stop the Spot campaign have shown that national monitoring of yellow spot is essential, enabling researchers at the Centre for Crop and Disease Management (CCDM) to stay ahead of any changes in the pathogen’s ability to infect crops.

The Curtin University and Grains Research and Development Corporation (GRDC) supported CCDM campaign will continue in 2016, aiming to develop tools and markers for wheat breeders to help them release more resistant varieties for growers.

CCDM yellow spot researcher Dr Pao Theen See, said her team received 145 samples in 2015, of which 56 per cent were confirmed to be infected with yellow spot.

“Yellow spot can be tricky to identify, in the past it has been mistaken as the cause for leaf yellowing, and is often confused with other leaf spot diseases,” Pao Theen said.

“Nevertheless, yellow spot infections were found to be widespread across Australia with the disease found in the western, southern and northern grain growing regions.”

How Stop the Spot helps researchers fight yellow spot, genetically

Yellow spot causes national wheat crop losses of $212 million, plus control costs of $463 million per annum.

By sending in leaf samples of yellow spot, researchers at the CCDM will be able to develop genetic tools for breeders, monitor biosecurity risks and have an understanding of how the pathogen may be changing in the paddock.

The yellow spot fungus disease, caused by the nectrotrophic fungal pathogen Pyrenophora tritici-repentis, is stubble-borne and secretes “effectors” – which are proteins secreted by the fungal pathogen that cause disease symptoms.

These effectors kill the cells of the wheat host, allowing the fungus to colonise the plant and feed from it.

Dr See said three effectors have already been found and described, with the most damaging effector, ToxA , supplied to wheat breeders to allow them to discard varieties that show sensitivity to this protein.

“We are also keeping a close eye out for ToxB, which causes chlorosis in wheat varieties that are sensitive to it, but is currently undetected in Australian pathogen samples,” Dr See said.

“As a major biosecurity risk to Australian wheat crops, it is extremely important we continue to monitor the yellow spot pathogen, and ensure ToxB remains outside of Australia.”

Key Findings

The main findings from genetic and molecular analysis of samples across Australia:

  • Yellow spot is nationally widespread
  • MR and MRMS varieties were found to be vulnerable to yellow spot infection
  • Australian yellow spot has one predominant race we know of (ToxA and ToxC)
  • ToxB was not detected, but it is currently present overseas and is a major biosecurity risk
  • No mutation was detected in the ToxA gene

For a more detailed report, click here.

I have yellow spot, what do I do now?

Please visit stopthespot for sampling instructions. Besides helping researchers develop new genetic tools that improve wheat yields, you will also receive feedback on your sample, confirming if it is yellow spot or not.

For information on how to manage the disease visit:

Follow the Centre for Crop and Disease Management on twitter @theCCDM

 

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