Mechanisms of herbicide resistance in weeds

In major field crops, synthetic herbicides have been used to control weeds worldwide. Globally, herbicide resistance in weeds should be minimized because it is a major limiting factor for food security. Cross resistance can occur with herbicides within the same or in different herbicide families and with the same or different sites of action. Multiple resistance refers to evolved mechanisms of resistance to more than one herbicide (e.g., resistance to both ALS-inhibitors and ACCase-inhibitors) and this resistance was brought about by separate selection processes. Target site resistance could occur from changes at the biochemical site of action of one herbicide. Non target site resistance occurs through mechanisms which reduce the number of herbicide molecules that reach the herbicide target site. There are currently 480 unique cases (species ${\times}$ site of action) of herbicide resistance globally in 252 plant species (145 dicots and 105 monocots). To date, resistance in weeds has been reported to 161 different herbicides, involving 23 of the 26 known herbicide sites of action. Finally, it can be concluded that we can protect crops associated to herbicide resistant weeds by applications of biochemical, genetic and crop control strategies.