Natural Products with Potential Use as Herbicides

Abstract

There is great incentive to discover effective and economically feasible herbicides that are toxicologically and environmentally benign.Several hundred active ingredients of herbicides are now sold world-wide. Virtually all of these compounds were discovered by screening compounds from organic chemical synthesis programs.Leads for the structure of one group of patented herbicides came from 1,8-cineole, a well known plant allelochemical. However, plants have thus far not been as lucrative as microbial products as a source of phytotoxic compounds with the potential for direct use as herbicides or as templates for new synthetic herbicide classes. Microbial phytotoxins have provided valuable information on potential molecular target sites for herbicides. This information has also been useful in probing the biochemistry of plants. Phosphinothricin (glufosinate when synthetic), a product of Streptomyces viridochromogenes, is a successful herbicide that is environmentally and toxicologically benign. Bialaphos, a tripeptide from S. hygroscopicus which degrades to phosphinothricin in target plants, is the only commercial herbicide produced by biosynthesis. Many other microbial products have been patented as herbicides and some of these are under active development.Most of these compounds are from non-plant pathogens; however, there is growing interest in utilizing plant pathogens as sources of herbicide leads. Tentoxin, cornexistin, and AAL-toxin are discussed in detail as examples of microbial toxins with the potential for herbicide development. An overview of natural phytotoxins that have been considered for herbicides is provided, as well as considerations of the pesticide industry in using this approach. This chapter not subject to U.S.

The floral volatile, methyl benzoate, from snapdragon (Antirrhinum majus) triggers phytotoxic effects in Arabidopsis thaliana

“…It has been shown previously that some plant VOCs have an eVect on the growth and seed germination of other plants Asplund 1968;Duke and Abbas 1995). Bate and Rothstein (1998) showed that aerial trans-2-hexenal quantitatively reduced Arabidopsis seed germination and root growth, similar to methyl jasmonate.…”

Allelopathic potential of orsellinic acid derivatives

“…Many secondary compounds of plants, microorganisms and lichens are known to be toxic to insect, microbes and other organisms. Many of these compounds have been used successfully, either in their natural or a modified form, as inseticides, fungicides and herbicides (Duke and Abbas, 1995). Phenolic substances are included in this group and an example is the herbicide "Letharal" -phytotoxic fraction of Lethariella canariensis.…”

Atividade alelopática do filtrado de cultura produzido por Fusarium solani

“…Essas toxinas podem agir sinergicamente com outras atividades do patógeno, desde que invada o tecido das plant as. 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).…”