Table 1.
HRAC classification and division of herbicides from the HRAC2020 and extended data sets across the MoA classesa.
| Legacy hrac code | hrac2020&wssa code | Number of compounds in hrac2020/extended set | General mode of action–targeted biological process | Mode of action–targeted molecular functions |
|---|---|---|---|---|
| A | 1 | 21/29 | Fatty acid biosynthesis | Inhibition of acetyl-CoA carboxylase (ACCase) |
| B | 2 | 58/61 | Amino acid synthesis (Leu, Ile, Val) | Inhibition of acetohydroxyacid synthase/acetolactate synthase (AHAS/ALS) |
| C1 | 5 | 43/53 | Photosynthesis (electron transfer) | Inhibition of photosystem (PS) II protein D1 (C1/C2 Ser264; C3 His215) |
| C2 | 5 | 30/37 | ||
| C3 | 6 | 5/9 | ||
| D | 22 | 4/5 | Photosynthesis (electron transfer) | Inhibition of diversion of the electrons transferred by the PS I ferredoxin |
| E | 14 | 29/43 | Photosynthesis (heme synthesis for chlorophyll) | Inhibition of protoporphyrinogen oxidase (PPO) |
| F1 | 12 | 7/9 | Photosynthesis (carotenoid synthesis) | Inhibition of phytoene desaturase (PDS) |
| F2 | 27 | 14/16 | Inhibition of 4-hydroxyphenylpyruvate dioxygenase (4-HPPD) | |
| F3 | 34 | 1/2 | Inhibition of lycopene cyclase | |
| F4 | 13 | 2/1 | Inhibition of 1-deoxy-d-xylulose-5-phosphate (DOXP) synthase | |
| G | 9 | 1/2 | Amino acid synthesis (Phe, Trp, Tyr) | Inhibition of 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase |
| H | 10 | 2/4 | Amino acid synthesis (Gln) | Inhibition of glutamine synthase |
| I | 18 | 1/3 | Tetrahydrofolate synthesis | Inhibition of dihydropteroate (DHP) synthase |
| K1 | 3 | 18/25 | Microtubule polymerization | Inhibition of microtubule assembly |
| K2 | 23 | 6/9 | Inhibition of microtubule organisation | |
| K3 | 15 | 43/39a | Fatty acid synthesis | Inhibition of VLCFAs |
| L | 29b | 6/6 | Cell wall synthesis | Inhibition of cellulose synthase |
| M | 24 | 6/8 | ATP synthesis | Uncoupling of oxidative phosphorylation |
| N | NAb | NAb/23 | Fatty acid synthesis | Inhibition of fatty acid elongase |
| O | 4 | 25/37 | Regulation of auxin-responsive genes | Synthetic auxin mimics -Stimulation of transport inhibitor response protein 1 (TIR1) |
| P | 19 | 2/3 | Long-range hormone signaling | Auxin transport inhibitors |
aIn the HRAC2020 classification there are additional classes Q (3), R (31), S (32) and T (33), all with up to 2 members 5.
bMajority of herbicides from the class N are fused in the K3 (15) class. The treating 23 herbicides of the legacy N class separately, does not affect the results since this subgroup is structurally diverse from the other K3 herbicides.