Poster: Hormones

Abs # 636: Does ethylene modulate herbicidal activity?

Presenter:	Silverman, F Paul , paul.silverman@valent.com
Authors	Silverman,  F Paul  (A)   Petracek, Peter D (A)   Ju, Zhiguo  (A)   Warrior, Prem  (A)
Affiliations:	(A): Valent Biosciences Corporation

The ethylene-releasing compound ethephon ((2-chloroethyl) phosphonic acid) is widely used in commercial agriculture. In an effort to better understand the role of ethylene in the activity of paraquat, a bipyridilium free radical-generating herbicide, we tested its activity on tobacco in the presence of ethylene-modulating chemicals. Simultaneous application of ethephon provided significant protection of tobacco from paraquat. However, the addition of antagonists of ethylene perception, 1-methylcyclopropene (1-MCP) or silverthiosulfate, to paraquat applications on tobacco did not affect its herbicidal activity. The co-application of aminoethoxyvinylglycine (AVG), an inhibitor of aminocyclopropane (ACC) synthase, did not affect paraquat activity while aminooxyacetic acid, an inhibitor of pyridoxal phosphate-dependent enzymes including ACC synthase, initially slowed the herbicidal activity, but did not protect plants after five days. Additional screening resulted in the identification of VBC-30015™, an inhibitor of ACC oxidase, which provided substantial protection from paraquat damage on tobacco and Arabidopsis. Simultaneous application of VBC-30015™ with paraquat resulted in a 60 percent decrease in the leaf area affected. In contrast, a significant activation of protoporphyrinogen oxidase inhibitors, a separate class of free-radical generating herbicides, was observed in further studies. Thus, the ability of both ethylene generators and inhibitors to modulate herbicidal activity may provide a novel method of controlling herbicidal and free-radical mediated processes.