CENTRE for Crop and Disease Management (CCDM) scientists have now discovered a fungicide resistant net blotch hybrid in Western Australia.
The research follows tests of barley samples from near Minlaton on South Australia's Yorke Peninsula last year which identified a new genotype in net form net blotch (NFNB) for the first time known, showing dual resistance to both a succinate dehydrogenase inhibitor (SDHI) fungicide as well as some Demethylation Inhibitor (DMI) fungicides.
CCDM Fungicide Resistant Management and Disease Impacts Theme leader, Dr Fran Lopez-Ruiz, said they not only discovered a fungicide resistant hybrid of the two common barley diseases, spot form net blotch (SFNB) and net form net blotch (NFNB), the hybrid was also a clone.
"We've known for a couple of years that hybrids of NFNB and SFNB exist in nature," Dr Lopez-Ruiz said.
"But now, not only do we know they exist, we also know they exist with multiple genetic mutations that make them highly resistant to some Group 3 fungicides.
"As well, they're also genetically identical - they're clones, which means they are reproducing asexually across the Esperance and South Stirling regions."
CCDM was first alerted by the Department of Primary Industries and Regional Development (DPIRD) in 2017 of fungicide failure in a paddock that had been treated multiple times with formulations containing Group 3 fungicides and was thought to be infected by SFNB.
After tests were carried out, with the hybrid first detected further samples were tested from seven additional sites across the South Stirling, Frankland, Amelup and Esperance regions, with hybrid clones detected up to 350 kilometres apart.
According to CCDM researcher Wesley Mair, tests found strains of the pathogen that were not only resistant to some Group 3 fungicides, but far more resistant than any NFNB or SFNB strain the team had ever studied.
Further genetic analysis found this type of net blotch carried known mutations for fungicide resistance in NFNB, and known mutations for fungicide resistance in SFNB.
"From further tests we are now convinced we have discovered a highly resistant hybrid," Mr Mair said.
In South Australia NFNB of barley had been identified as fungicide resistant to some actives compounds from within two fungicide chemical groups, Group 7 (Succinate dehydrogenase inhibitors -SDHIs) and Group 3 (Demethylase inhibitors (DMIs).
