South Australian researchers have discovered what is believed to be the first case of "gene amplification" herbicide resistance in an Australian weed species.
The mechanism has been found in glyphosate resistant strains of brome grass, a significant crop weed in southern and western Australian cereal growing zones.
Dr Jenna Malone, from the University of Adelaide, said the finding could ultimately help farmers, who can't afford to lose glyphosate from their weed control toolkit.
"From a management side, there aren't many herbicide options for the control of brome," she said.
"So in the case of resistance, the loss of glyphosate would cause serious management issues for farmers.
"At the moment, it [resistance] is not overly widespread. The first case we identified was here in South Australia, on the Yorke Peninsula, then one case in Victoria.
"Since then we've identified three further cases, two more from Victoria and one in SA.
"Hopefully if we can get on top of the problem, and get farmers aware that it is something that might be developing, then hopefully we can get onto the management before it is a bigger issue."
Gene amplification likely to emerge in other weed species
Plants displaying the gene amplification mechanism are able to produce more of the enzyme EPSPS, which is targeted by glyphosate, to overcome the herbicide's action.
Dr Malone said it was possible the mechanism would now emerge as a cause of herbicide resistance in other Australian weed species.
"The usual ways we see resistance occurring is through degradation of the herbicide by the plant," she said.
"Also through mutations in the target of the herbicide, or the plant being able to control the movement of the herbicide.
"But in the case of brome we've seen quite a different mechanism to this. It's the first time we've seen this in an Australian weed species.
"It is possible other species will develop this mechanism of resistance. In America, there have been three species so far that also have this mechanism."
Dr Malone said the case highlighted the need for sound weed management strategies on the farm.
"The finding of another instance of resistance reinforces the need to not overuse particular herbicides, in this case glyphosate," she said.
"And to employ good practices of diverse weed management, including crop rotations, fallow periods, interspersing with grazing cycles and other control mechanisms."
Source - www.abc.net.au
