Invited Paper: Chemicals from nature for weed management

Abstract

Natural products represent a vast repository of materials and compounds with evolved biological activity, including phytotoxicity. Some of these compounds can be used directly or as templates for herbicides. The molecular target sites of these compounds are often unique. Strategies for the discovery of these materials and compounds are outlined. Numerous examples of individual phytotoxins and crude preparations with weed management potential are provided. An example of research to find a natural product solution of a unique pest management problem (blue-green algae in aquaculture) is described. Finally, the problems associated with natural products for pest control are discussed.

Atividade alelopática do filtrado de cultura produzido por Fusarium solani

“…Suas utili zações diret as como bioerbicidas ou como estrutura básica para o desenvolvimento de novas classes de herbicidas vêm recebendo cada vez mais atenção, não só por parte da comunidade científica, mas também pelas empresas que se dedicam à produção de defensivos agrícolas (Duke & Abbas, 1995;Hoa gla nd, 1990). Alg uns traba lho s for am desenvolvidos nos últimos anos visando identificar e caracterizar a atividade biológica de toxinas produzidas por fungos (Gerwick et al, 1997;Strobel et al, 1991;Duke et al, 2002;Metha & Brognin, 2000). Dentre as características importantes dessas toxinas, podem-se destacar a alta atividade específica e a alta seletividade, além de serem, ainda, biodegradáveis (Cutler, 1988).…”

Allelopathy: driving mechanisms governing its activity in agriculture

“…To date, some commercial herbicides derived from plants or microorganisms that have already been introduced onto the market belong to different chemical groups, with entirely novel MeA (Duke et al 2002;Dayan et al 2012). The need for new herbicide MeA should be emphasized for at least three important reasons: (a) no new herbicide MeA were released onto the market within the past two decades; (b) the number of herbicides launched onto the market is decreasing steadily, especially due to registration issues; and (c) limitations of current herbicides due to herbicide-resistant weeds are increasing (Duke 2012).…”

“…In a review that highlighted 30 phytotoxins produced by microorganisms and plants, 23 different MeA were identified (Duke et al 2002). Additionally, twelve new MeA were documented within 14 compounds isolated from microorganisms and four new mechanisms were discovered in compounds from four different plants species (Dayan et al 2012).…”

“…Additionally, twelve new MeA were documented within 14 compounds isolated from microorganisms and four new mechanisms were discovered in compounds from four different plants species (Dayan et al 2012). The main MeA of herbicides include: (a) inhibition of photosystem II electron transport; (b) interruption of respiration and adenosine triphosphate synthesis; (c) mediation by reactive oxygen species (ROS); (d) alternative mechanisms, mainly the action on amino acid synthesis and plant growth regulators (auxins and gibberellins); (e) indirect allelopathic effects ); (f) inhibition of photosystem I; (g) inhibition of tubulin polymerization; and (g) action on RNA polymerase (Duke et al 2002), among others.…”

Atividade alelopática de chalcona sintética, de seus precursores e de cetonas e aldeídos relacionados

“…Muitas dessas mol éculas agem sobre o met abolis mo das plantas, de forma semelhante aos herbicidas, constituindo-se em substitutos aos produtos sintéticos disponíveis no mercado (Kenfield et al, 1988;Strobel et al, 1991;Duke et al, 2000Duke et al, , 2002Einhellig, 2001). Paralelamente, as informações disponíveis apontam para existência de similaridades entre os sítios moleculares de ação dos produtos sintéticos com as molécu-las naturais (Duke & Abbas, 1995).…”