Resistance Mechanisms

January 17, 2022

AHRI 2021 Wrap-Up

Written by: Jessica Scholle Despite the challenges COVID-19 presented in 2021, our researchers continued their research and published throughout the year. From the identification of…

March 31, 2021

2,4-D synergises metribuzin

Synergy between herbicides is rare, but extremely sort after and this synergy is often claimed but it takes a specific research technique to confirm the synergy. Australian farmers and agronomists have previously observed synergy between phenoxy herbicides (2,4-D) and PSII herbicides (Group C / Group 3 herbicides such as metribuzin) and now we know why, thanks to this new AHRI research.

February 1, 2021

We’ve cracked the P450 code

About 35 years ago a ryegrass population that had been sprayed several times with Hoegrass® (Diclofop) became resistant to that herbicide and cross resistant to Glean (chlorsulfuron) before Glean® or any other ALS herbicide had ever been used in Australia.

P450 enzymes were suspected to be the cause of this cross resistance but it has taken until now to get the definitive evidence.

A very patient group of researchers led by Heping Han from AHRI, including researchers from Bayer and Zheijiang University in China have identified the P450 gene responsible for cross resistance to herbicides of at least five modes of action.

November 3, 2020

2,4-D antagonises glyphosate, especially in glyphosate resistant weeds

Some recent research by a former AHRI researcher Jingbo Li and others shows that glyphosate resistance changes this. They studied two populations of barnyard grass with relatively low-level glyphosate resistance and found that when 2,4-D Amine or Ester was added to the tank with glyphosate, barnyard grass control was greatly reduced. They went on to discover that this is due to an effect on uptake and translocation.

April 7, 2020

Diflufenican resistance in wild radish is by P450s

In 1999 I was refuelling my car at a petrol station in Geraldton when I bumped into Dave, a technician with the local Department of Ag. Dave told me he had just returned from a trial where wild radish had survived 600 mL/ha of diflufenican (e.g. Brodal®). This was three times the maximum label rate and six times the common use rate at the time. I could see the entire lupin industry unravelling in front of my eyes. Lupins were a huge success story on our sandplain soils in the area, wild radish was their main Achilles heel…

February 12, 2020

Group H (HPPD) resistant wild radish

The first resistance to HPPD herbicides in wild radish has now been discovered by AHRI researchers led by PhD candidate Huan Lu. Wild radish is just the third weed in the world to evolve resistance to this group of herbicides. The wild radish in this research was resistant to several other groups of herbicides which may have led to metabolic resistance to HPPD.

November 11, 2019

World’s first metabolism-based glyphosate resistance discovered

Wine casks, plastic banknotes, WiFi, the refrigerator, lawnmower and the humble ute (pickup truck) are all Australian, world-first inventions. Which of these makes the biggest difference in your life? As long as it’s not the wine cask you’re doing just fine!

We now have a world first in herbicide resistance. research by visiting Chinese researcher to AHRI, Dr Pan Lang under the watchful eye of Qin Yu, concluded that they were looking at the world’s first case of metabolism-based resistance to glyphosate. The culprit? Click through to find out!

September 10, 2019

Is there an invisible gorilla in your paddock?

Huan Lu’s been investigating a population of wild radish that has the infamous Ser-264-gly mutation. This is the target-site mutation that is behind TT canola and makes wild radish highly resistant to PSII-inhibiting herbicides like atrazine and, to a lesser extent, metribuzin.

But, he wondered if there was more to this resistance than first meets the eye. Does focusing on the strong 264 mutation mean that we could fail to identify other important resistance mechanisms?

April 15, 2019

Trifluralin resistance is different – recessive inheritance

We once thought that the genetics of eye colour was simple. Both parents have blue eyes, therefore, all of their children will have blue eyes. Easy peasy! Then science progressed and we realised that it isn’t actually that simple because several genes are involved. The genetics of herbicide resistance was simple. One parent is resistant to a herbicide, therefore, all of the offspring will be resistant because the gene is dominant or semi-dominant. This is true for almost all cases of herbicide resistance and was easy to understand. Until now. Click to read more about PhD student Jinyi Chen’s research.

February 19, 2019

Wild radish resistant to Atrazine, super-sensitive to Bromoxynil

By Peter Newman Alexander Graham Bell famously said, “When one door closes another door opens, but we so often look so long and so regretfully…