Tolerance and susceptibility are what we expect to see when a selective herbicide is used on a mixed population of plant species that results from differential retention, penetration, translocation, or metabolism. Resistance is the ability of a formerly susceptible plant population to survive herbicide doses above those that were once used to control the original plant population. Resistance is most frequently caused by a single gene mutation that modifies the herbicide binding site on an enzyme or protein. Multiple resistance - weed populations that are resistant to two or more herbicides from different chemical groups with different modes of action. Multiples resistance is less frequent than cross resistance and is frequently attributed to differential retention, penetration, translocation, or metabolism rather than to site of action.
Resistance occurs in weed populations by naturally-occurring mutations.
These mutations are not induced by herbicide applications. The rate of increase of herbicide-resistant weeds is difficult to observe because the proportion of resistant weeds remains very low initially. At some point, a single additional treatment will result in a major weed control failure. STS Transgenic herbicide resistant crops as the product of genetic engineering A gene that confers glyphosate resistance was transfer red from the bacterium Agrobacterium sp. to crops. Glufosinate-resistant crops resulted from transfer of a gene from the bacterium Streptomyces viridochromogenes.