Why are ALS inhibitors at high risk for developing resistance?

ALS inhibitors, or acetolactate synthase inhibitors, work by targeting a specific enzyme that is crucial for the biosynthesis of amino acids in plants. This site-specific mechanism of action is what makes them particularly susceptible to the development of resistance. When a herbicide affects a specific target site in the plant, any mutations in that site can lead to plants that are less affected or completely resistant to the herbicide’s effects.

Because ALS inhibitors impact a narrow range of biological targets, plants with a single genetic mutation can survive an application, reproduce, and pass on this resistance trait to future generations. Therefore, over time, the populations of the targeted weeds can shift towards those that possess resistance to ALS inhibitors, leading to more significant challenges in weed management.

In contrast, herbicides that have broad-spectrum action or are non-selective generally affect multiple pathways and therefore do not create the same intense pressure for resistance development as those that are highly specific. Similarly, while widespread environmental distribution can pose various challenges, it does not inherently lead to resistance formation as directly as the site-specific action of ALS inhibitors does.