Allelochemicals Biologica... - Name

ROBERT J. KREMER
THE ROLE OF ALLELOPATHIC BACTERIA IN
WEED MANAGEMENT
U.S.D.A., Agricultural Research Service, Cropping Systems & Water Quality
Unit, University of Missouri, Columbia, Missouri, U.S.A.
Email: KremerR@missouri.edu
Abstract. Allelopathic bacteria encompass those rhizobacteria that colonize the surfaces of plant roots, produce,
and release phytotoxic metabolites, similar to allelochemicals, that detrimentally affect growth of plants. Practical
application of this group of bacteria to agriculture could contribute to biological weed management systems that
have less impact on the environment than conventional systems by reducing inputs of herbicides. Allelopathic
bacteria have been investigated for potential as inundative-type biological control agents on several weeds.
Because allelopathic bacteria generally do not attack specific biochemical sites within the plant, unlike
conventional herbicides, they offer a means to control weeds without causing direct selective pressure on the
weed population, therefore, development of resistance is not a major consideration. Additionally, the use of
allelopathic bacteria appears to be environmentally benign relative to herbicides. These characteristics make
allelopathic bacteria an attractive approach for managing crop weeds in a sustainable manner, even within the
boundaries of conventional agriculture systems. However, recent evidence suggests that indigenous allelopathic
bacteria might be exploited under certain crop and soil management practices that are inherently part of sustainable
agricultural systems. The development of “weed-suppressive” soils in diverse sustainable systems is encouraging
because indigenous populations of allelopathic bacteria may develop in several soils and environments using
similar practices. The recent demonstrations of apparent weed-suppressive soils may lead to development of
specific management strategies for the establishment and persistence of native allelopathic bacteria directly in
soils conducive to annual weed infestations.
1. INTRODUCTION
Biological weed management is a system that incorporates the use of diverse biological
organisms and biologically-based approaches including allelopathy, crop competition,
and other cultural practices to significantly reduce weed densities in a manner that is
similar to use of chemical herbicides alone (Cardina, 1995). Interest in developing
effective biological weed management systems continues to increase because of a
growing awareness of problems associated with the constant and intensive use of
chemical herbicides, which include surface- and groundwater contamination,
detrimental impacts on nontarget organisms, development of weeds resistant to
herbicides (including those that are used in transgenic herbicide-resistant crops), and
consumer concerns for residues on food (Gliessman, 2002). A component of biological
weed management involves biological control, the intentional use of living organisms
(insects, nematodes, fungi, and bacteria) to reduce the vigor, reproductive capacity,
density, or impact of weeds (Quimby and Birdsall, 1995). A number of reviews are
143
Inderjit and K.G. Mukerji (eds.),
Allelochemicals: Biological Control of Plant Pathogens and Diseases, 143– 155.
© 2006 Springer. Printed in the Netherlands.