(Photo: samples of suspected resistant strains came from Buenos Aires province)

Buenos Aires, July 1st, A team from the Buenos Aires University confirmed the resistance of fungus causative of the tan spot (Drechslera tritici-repentis) disease in wheat to the strobilurins. Farmers had been warning about the persistence of some fungus diseases after one or two fungicides treatements.

The team conducted by phytopatologists Marcelo Carmona and Francisco Sautua collected samples from suspected farms where fungicides inefficiency was claimed.

The samples were collected from Buenos Aires province, the large wheat province producer in the country. The samples were tested with the application of 100 ug/mL of each mollecule most common used by farmers: azoxystrobin, pyraclostrobin and trifloxystrobin.

The researchers used a high dose of the active principe to easily discriminate between susceptible and resistant strains. Ninety percent of the samples grew at this dose, confirming the resistance.

The molecular study showed that all the resistance strains had the G143A mutation, which confers a strong resistance to the strobilurins.
Researchers also tested fungus resistance to triazole, exposing them to a 60 ug/ml dose. In this case, they found that some isolated showed growth to some active principles. For the others, the experimental dose inhibited cent percent of the isolateds. “Due to the triazole resistance is a more complex process, this work is still under studio”, researchers conclude.