Location: Natural Products Utilization Research
Title: Clues to new herbicide mechanisms of action from natural sources Authors
Submitted to: American Chemical Society Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: April 1, 2013
Publication Date: September 25, 2013
Citation: Duke, S.O., Dayan, F.E. 2013. Clues to new herbicide mechanisms of action from natural sources. American Chemical Society, Washington, DC. Pest Management with Natural Products. p. 203-215. Interpretive Summary: The last commercial herbicides to introduce a new mode of action were the HPPD inhibitors launched more than 20 years ago. There is a growing need for new modes of action because of the increasing evolution of target site-based herbicide resistance in weeds. Natural compounds have been and continue to be good sources of new herbicide molecular target sites. In the past, glufosinate and the triketone herbicides were derived from natural compounds and introduced important new modes of action. In particular, plant pathogens are good sources of phytotoxins. The modes of action of natural product phytotoxins, such as leptospermone, tentoxin, actinonin, hydantocidin, thaxtomin, coronatine, AAL-toxin, and other natural products or natural product derivatives are discussed.
Technical Abstract: More than 20 years have passed since the last herbicide with a new mode of action (MOA) was introduced (1). Before this time, a new herbicide MOA was introduced about every 2.5 to 3 years (2), accumulating to the approximately 20 MOAs that are now available (1). During the past 20 years, the incidence of evolved, target-site-based herbicide resistance has more than doubled (3), with a growing incidence of multiple resistance to herbicides with different MOAs within the same weed species (e.g., (4). All strategies mitigating or delaying the evolution of resistance to herbicides rely on the utilization of complementing weed management practices, including rotation of herbicide MOAs or combining MOAs in tank mixes or sequential sprays in the same growing season (e.g., (5). As more weeds evolve resistance to the herbicides with the currently available MOAs, the need for herbicides with new MOAs to maintain MOA diversity becomes more critical. Natural compounds offer a source of molecules that are phytotoxic through MOAs that are not exploited by current herbicides (6). This short chapter provides examples of natural compounds that kill plants by MOAs that are not shared by commercial herbicides and discusses the prospects for use of natural compounds both as tools for new MOA discovery and as templates for new herbicide chemistries that are affected at unexploited molecular target sites. The examples we provide are divided into phytochemicals and microbial phytotoxins.