AGRO 107 |
| Acetyl-CoA carboxylase (ACCase) performs the first committed step of fatty acid synthesis, i.e., production of malonyl-CoA from acetyl-CoA. Most grasses have a homomeric form of ACCase in plastids, and this enzyme is the site-of-action for ACCase-inhibiting aryloxyphenoxypropionate, cyclohexanedione, and phenylpyrazolin herbicides. In contrast, most dicotyledonous plants have a heteromeric form of plastidic ACCase, which is not inhibited by herbicide. Decreased metabolic activation and/or increased metabolic detoxification relative to grass weeds provides herbicide tolerance to some grass crops with sensitive plastidic ACCase. While selective control of grass weeds with ACCase inhibitors remains effective in most instances, recurrent use has selected for biotypes resistant to these herbicides. Several naturally-occurring plastidic ACCase mutations have been identified as likely conferring herbicide resistance among grass weeds. Metabolism-based resistance involving detoxification enzymes is also an important resistance mechanism. The specific molecular cause of resistance in individual weed biotypes directly affects resistance magnitude for individual herbicides. |
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Weed Resistance to Herbicides
1:30 PM-4:15 PM, Tuesday, 12 September 2006 San Francisco Marriott -- Salon 3, Oral
Division of Agrochemicals |