Biorational Control of Weeds and Fungi with Peptides

Abstract

Tentoxin is a cyclic tetrapeptide produced by the fungus Alternaria alternata that disrupts chloroplast development in most of the major weed species in soybean and johnsongrass in corn while having no effect on either of these crop species. The major impediment to the development of tentoxin as a herbicide is its limited availability because of low biosynthetic yields. Iturins are a family of cyclic octapeptides having a unique β-amino acid, iturinic acid, incorporated into the peptide backbone. Iturins have a broad antifungal activity, but low biosynthetic yields may limit their commercialization. Chemical synthesis of both molecules is possible and the production of analogues has led to meaningful structure/activity relationships. To date no analog has provided greater activity or specificity than the parent molecule for either of the two agents. Molecular genetic manipulation is considered the best strategy for the increase in production of both of these compounds for cost effective synthesis. Success of cloning of the biosynthetic genes may determine the eventual deployment of these biorational pesticides.The cost of pest control in agriculture is staggering; direct costs of pesticides are estimated to be at least $20 billion annually, with unestimated indirect costs making the exact amount impossible to accurately state. Recent popular concern for the environment and legislation toward banning some of the more traditional pesticide compounds has led to the development of new strategies for the control of pests which include microbes as biological control organisms and the use of the biorational approach in which natural products provide a basis for the This chapter not subject to U.S.