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Fast-tracking botrytis fungicide resistance identification

RD&A News | October 2020
09 Oct 2020
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A rapid, simple and cost-effective test to detect and quantify fungicide resistant botrytis in a vineyard setting has been successfully demonstrated in Western Australia.

It’s an exciting development, as the method has the potential to allow growers to adjust or modify fungicide applications within an hour of the discovery of suspected infected grape berries.

Previously developed at Curtin University for characterising wheat powdery mildew resistance, the method was adapted to detect fungicide-resistant botrytis (Botrytis cinerea) in the Wine Australia-funded project: Managing fungicide resistance in Australian viticulture.

The test uses a quantitative polymerase chain reaction technique (qPCR) to target a particular mutation linked with fungicide resistance in Botrytis cinerea. qPCR is a technique whereby a mutation of interest is amplified over successive cycles and DNA quantities are measured at each of these cycles.

The method – a snapshot look

The test is simple: individual infected berries are taken from the vineyard and ground by hand for 30 seconds in a tube. The mixture is diluted, reagents added and a qPCR test is run for 50 minutes in a lightweight qPCR machine. A result on the fungicide resistance status is provided via analysis software on a laptop computer.

The results can then provide growers with much needed information on the frequency of AnilinoPyrimidine (AP) resistance in a particular block. APs are highly active fungicides commonly used against a broad range of fungi.

‘Growers have valuable information that can assist them in maintaining good resistance management practices and reducing the economic impact of the disease’, explained Principal Investigator, Lincoln Harper from Curtin University.

‘In turn, resistance frequency information can help in the adjustment or modification of existing fungicide application programs, if necessary, with respect to AP fungicides.’

If resistance isn’t detected but you have field failure of AP, then you know that you may need to adjust your spray application to improve efficacy.

The method was recently successfully trialled by Western Australian growers.

‘Growers brought in a small number of infected bunches for analysis and literally received results on their fungicide resistance status to botrytis in an hour or so’, said Project Leader, Mark Sosnowski from the South Australian Research and Development Institute (SARDI).

He said the research group was excited about the potential of expanding the test in the future.

‘Curtin University have already begun working with the SARDI team to include powdery mildew resistance to certain fungicides. Ultimately, we hope to undertake a roadshow towards the end of the project in the 2021–22 season to demonstrate this technology across the wine sector.’

Project supervisor Dr Francisco Lopez Ruiz from Curtin University said the method could be used not only to quantify mutations, but any organism – provided there was enough DNA in the sample.

‘Viruses, bacteria, fungi, oomycetes and aphids are all potential suitable targets of this tool’, he said.

Strategies to control botrytis

Scott Paton from Nufarm Research and Development offered the following strategies to help control botrytis:

  • Calibrate your sprayer annually, both for nozzle output and fan positioning.
  • Check that your water volumes match the canopy structure throughout the season.
  • Take some time before the season or even before key sprays to match use rates, concentration factors and required water volumes to ensure the correct dose is being applied.
  • Remember: it’s not just about growth stages! Growing conditions and vineyard factors can significantly impact on disease loads and these don’t always coincide with traditional fungicide growth stage targets.     
  • Consider the entry points that contribute to disease pressure in the vineyard, and use an adaptive preventative program to dial down disease pressure before it becomes a problem.

For more botrytis management strategies using agrochemicals, refer to the Dog Book available here.  

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This content is restricted to wine exporters and levy-payers. Some reports are available for purchase to non-levy payers/exporters.