Fungicide resistance: Genetic mutation detected in SA

Here’s everything you need to know about Australia’s first detection of a genetic mutation reducing sensitivity to common fungicides.

Barley farmers should be on the watch for the cereal disease net blotch after the detection of a genetic mutation in a South Australian barley crop. Pictured: spot form of net blotch in a cereal crop.

Barley growers are being warned to keep a close eye on their crops after researchers detected Australia’s first instance of a genetic mutation reducing sensitivity to a common group of fungicides.

Germany-based chemical producer BASF reported on Wednesday it had detected a mutation known as F129L in barley leaf samples infected with a cereal disease known as ‘net form of net blotch’.

The samples were collected during a product trial in the Yorke Peninsula, South Australia, in October last year, and sent to Germany for genetic analysis, the company said in a statement.

BASF crop protection head of development Ian Francis warned the company “found the mutation randomly, so it’s likely to be more widespread”.

Net form of net blotch (scientific name pyrenophora teres f.sp. teres) is considered the most damaging disease in Australian barley crops.

The infection kills leaves prematurely and can reduce the weight and number of grains on a plant, leading to yield reductions of up to 30 per cent and quality downgrades.

The F129L mutation already exists overseas, and is “known to reduce the effectiveness of Group 11 fungicides … on barley net blotch”, the BASF statement said.

Group 11 fungicides are classified as quinone outside inhibitors. Reduced sensitivity to the fungicide group has previously been detected in Europe and Canada.

Mr Francis said the F129L mutation “doesn’t necessarily create full QoI resistance in net blotch. However, barley growers and agronomists now need to be even more mindful of their management strategies for the disease.”

“As a matter of good stewardship, we should be on the lookout for it and growers should be proactive in their rotation of different fungicide groups,” he said.

Fungicide resistance in Australia as at July 2013 (latest BASF detection not included). Picture: Australian Fungicide Resistance Extension Network

Resistance to fungicides increasing

The news of BASF’s detection comes just two weeks after researchers in Queensland discovered the state’s first cases of fungicide resistance in powdery mildew.

The researchers, from the Centre for Crop and Disease Management and the NSW Department of Primary Industry, discovered wheat powdery mildew with resistance to QoI fungicides, and “very high levels of resistance to DMI fungicides such as propiconazole and prothioconazole”.

The high frequency of the DMI resistance mutation in the pathogen population indicated that the mutation may have been on Queensland farms “for a number of years”, while the lower frequency of the QoI resistance indicated either “this is a relatively new change to Queensland’s pathogen population, or that growers use less QoI than DMI fungicides to control wheat powdery mildew”, according to a statement on the CCDM website.

Careful management is key

To limit fungicide resistance, growers have been cautioned to regularly change the fungicide group they use, follow label directions and not spray more than necessary.

Net blotch has already developed resistance and reduced sensitivity to other fungicide groups, so growers have limited options to control the disease.

In Victoria, reduced sensitivity has been reported for Group 3 fungicides for both spot form net blotch and net form net blotch.