Herbicides, resistance induction

These experiments demonstrate that the pathways for inducing CYPs involved in herbicide detoxification in wheat and L, rigidum can be different. In addition, a different pattern of induction occurs in herbicide-resistant L rigidum plants compared to susceptible plants. 

Natural products represent an immense reservoir of new molecules for the development of pesticide agents. In particular, natural products based herbicides have become attractive in recent years for a few reasons. One of the reasons is that they are environmentally benign. Furthermore, the novelty of their structures offers the possibility of finding compounds with new mode of actions, thus diminishing the induction of plant resistance, a problem associated with commonly used synthetic herbicides. 

Lolium biotypes exist which have resistance to the sulfonylurea herbicides chlorsulfuron and metsulfuron methyl (4). The biotype used in the studies presented here is resistant to both these sulfonylurea herbicides. Sulfonylurea herbicides inhibit the chloroplastic enzyme acetolactate synthase (ALS), also known as acetohydroxyacid synthase (AHAS) (16). Inhibition of this enzyme results in disruption of the synthesis of the branched-chain amino acids valine and isoleucine (161. The imidazolinone herbicides also inhibit ALS Q2). In some species auxins can protect against chlorsulfuron inhibition (S. Frear, USDA North Dakota, personal communication) the mechanistic basis for this protection is not known. We have measured the ALS activity in the resistant and susceptible Lolium and have also checked for any induction of ALS activity following treatment with the sulfonylurea herbicide chlorsulfuron. 

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