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The ecology and chemistry of novel allelochemicals in graminaceous root exudates and their potential utilization as bioherbicides

L.A. Weston, X. Yang, C. Bertin and B. Scheffler.

Department of Horticulture. Cornell University. Ithaca NY 14853. law20@cornell.edu

Abstract

Roots of many weed and crop species contribute mixtures of biologically active chemicals into the environment through their root exudates. Root exudates are known to influence growth and establishment of crop and weed species and are released by living roots or root hairs. Many perennial plants have extensive root systems which can produce prolific amounts of exudates and bioherbicides within these exudates over time. We have isolated and identified a number of biologically active novel secondary products from the exudates of graminaceous species, including Sorghum spp., Festuca spp. and Secale spp. Root exudation in these species can be modified by physical factors such as oxygen availability, ethylene production and drought stress or water availability. The production of long chain hydroquinones by sorghum spp. and amino acid analogues by fescue spp. are unique examples of crop species which effectively suppress the growth of germinating weed seeds and alter the soil rhizosphere by production of biologically active plant growth inhibitors over time. The mode of action of these products is similar to that of other synthetic soil-applied herbicides including the phenyl ureas and triazines (photosystem II inhibitors) and the dinitroanilines (mitotic disrupters). We have focused most recently on localization of site of production of these bioactive exudates and expression and isolation of key genes involved in their biosynthesis and release from living root cells. Novel genes related to sorgoleone biosynthesis have been isolated using a modified form of differential display technology; currently we are evaluating this technique with Festuca spp. germplasm.

Media summary

Many plant roots exude bioherbicides. We have isolated and identified a number of novel biologically active exudates from graminaceous species, including Sorghum spp., Festuca spp. and Secale spp.

Keywords

Bioherbicides, differential display; root exudates, sorgoleone biosynthesis

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