glyphosate resistance

Resistance to the widely used herbicide, glyphosate, has evolved through target-site CNV in many weedy plant species, including the economically important grass, Eleusine indica (goosegrass); however, the origin and mechanism of these CNVs remain elusive in many weed species due to limited genetic and genomic resources.

We have previously demonstrated that an aldo-keto reductase (AKR) from Echinochloa colona (EcAKR4-1) can metabolize glyphosate and confers glyphosate resistance. This study aims to investigate if the EcAKR4-1 orthologs from Lolium rigidum also play a role in glyphosate resistance in non-target-site based, glyphosate-resistant (R) L. rigidum populations from Western Australia.

ABC transporter genes are present in plants and now a specific ABC transporter has been shown to endow resistance to the herbicide glyphosate, in a similar way to the way these ABC transporters can give resistance to anti-cancer drugs in humans. This is the first time that a plant ABC transporter has been found responsible for herbicide resistance. 

The objective of this study was to determine whether a jungle rice population from the tropical Ord River region of northwest Australia was glyphosate-resistant and whether alternative herbicides labelled for jungle rice control were still effective. Seed samples collected from the field site were initially screened with glyphosate in the glasshouse, and surviving individuals were self-pollinated for subsequent glyphosate dose-response studies. Glyphosate resistance was confirmed, as the suspected resistant population was found to be 8.6-fold more resistant to glyphosate than a susceptible population-based on survival (LD50 of 3.72 kg ha21), and 5.6-fold more resistant based on biomass reduction (GR50 of 1.16 kg ha21).

In this research, it was first established that Tridax, a global tropical weed species, evolved glyphosate resistance in the Ord River irrigation area in north-western Western Australia. This is the first report of glyphosate resistance in Tridax. The mechanism of glyphosate resistance was studied.  Various possible resistance mechanisms were NOT responsible for resistance (EPSPS gene amplification, different glyphosate uptake or translocation). In this glyphosate-resistant Tridax population, the glyphosate resistance mechanism is a mutation in the EPSPS gene causing substitution at amino acid 102 (Thr-102-Ser). 

Transgenic glyphosate-resistant canola was first commercially grown in Western Australia (WA) in 2010, providing an opportunity to obtain important baseline data regarding the level of glyphosate resistance in weeds following the exclusive use of glyphosate for in-crop weed control. In this study, two surveys (2010 and 2011) were conducted across the 14 Mha of the grainbelt of WA.

This study confirms and characterises glyphosate resistance in two polyploid Echinochloa colona populations from north-eastern Australia.

Glyphosate is the most important and widely used herbicide in world agriculture. Intensive glyphosate selection has resulted in the widespread evolution of glyphosate-resistant weed populations, threatening the sustainability of this valuable once-in-acentury agrochemical. Field-evolved glyphosate resistance due to known resistance mechanisms is generally low to modest.

In Australia, glyphosate has been used routinely to control wild radish (Raphanus raphanistrum L.) for the past 40 years. This study focuses on two field-evolved glyphosate-resistant populations of wild radish collected from the grainbelt of Western Australia.

Weed populations can have high genetic plasticity and rapid responses to environmental selection pressures. For example, 100-fold amplification of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene evolved in the weed species Amaranthus palmeri to confer resistance to glyphosate, the world’s most important herbicide.