Target-Site Mutation Search Tool

The target-site resistance search tool was developed to find known target-site mutations that confer target site resistance in weed species. This tool can search for known mutations in nucleotide sequences coding for acetolactate synthase (ALS, also known as AHAS), acetyl-CoA carboxylase (ACCase), photosystem II psbA (psbA), 5-enolpyruvyl shikimate 3-phosphate synthase (EPSPS), alpha-tubulin associated with mitotic herbicide resistance (alpha-tubulin), and protophorphyrinogen oxidase (PPO). To use the tool, copy and paste your search string into the sequence box and select your desired target-site. A command-line tool is available on GitHub (

Nucleotide Sequence:
Target Site:

The following target site mutations are search for the individual target sites. ALS: Ala-122, Pro-197, Ala-205, Asp-376, Trp-574, Ser-653, Gly-654 ACCase: Ile-1781, Trp-1999, Trp-2027, Ile-2014, Asp-2078, Cys-2088, Gly-2096 psbA: Val-219, Ser-264 EPSPS: Gly-101, Pro-106 Alpha-tubulin: Thr-239, Met-268 PPO: Gly-210 codon deletion, Arg-98 (more appropriate referred to as Arg-128 based on Amaranthus) PLEASE REPORT ANY BUGS TO Dr. McElroy. We have run numerous test cases on the search tool but as with any code there could be a case that might cause the search to fail.