Table Of ContentNatural Resistance of Plants
to Pests
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ACS S Y M P O S I UM SERIES 296
Natural Resistance of Plants
to Pests
Roles of Allelochemicals
1 Maurice B. Green, EDITOR
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6.f Independent Consultant
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6- Paul A. Hedin, EDITOR
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k- Boll Weevil Research Laboratory
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6 | Developed from a symposium sponsored by
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1 the Division of Pesticide Chemistry
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Dat April 28-May 3, 1985
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American Chemical Society, Washington, DC 1986
Library of Congress Cataloging in Publication Data
Natural resistance of plants to pests.
(ACS symposium series, ISSN 0097-6156; 296)
"Developed from a symposium sponsored by the
Division of Pesticide Chemistry at the 189th Meeting of
the American Chemical Society, Miami Beach, Florida,
1 April 28-May, 1985."
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w Includes indexes.
96.f 1. Allelopathic agents—Congresses. 2. Pests—
02 Biological control—Congresses. 3. Insect-plant
6- relationships—Congresses.
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1 I. Green, Maurice B. (Maurice Berkeley) II. Hedin,
bk- Paul A. (Paul Arthur), 1926- . III. American
1/ Chemical Society. Division of Pesticide Chemistry.
02 IV. American Chemical Society. Meeting (189th: 1985:
0.1 Miami Beach, Fla.) V. Series.
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doi: QISKB8N9 80.A-84431N2-3089 50-21 986 58l.5'249 85-28748
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n Copyright © 1986
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ati American Chemical Society
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bli All Rights Reserved. The appearance of the code at the bottom of the first page of each
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PRINTED IN THE UNITED STATES OF AMERICA
ACS Symposium Series
M. Joan Comstock, Series Editor
Advisory Board
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96.f Harvey W. Blanch Donald E. Moreland
02 University of California—Berkeley USDA, Agricultural Research Service
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k-1 Alan Elzerman W. H. Norton
1/b Clemson University J. T. Baker Chemical Company
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0. John W. Finley James C. Randall
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oi: Nabisco Brands, Inc. Exxon Chemical Company
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8 Marye Anne Fox W. D. Shults
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6, 1 The University of Texas—Austin Oak Ridge National Laboratory
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ar Martin L. Gorbaty Geoffrey K. Smith
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an Exxon Research and Engineering Co. Rohm & Haas Co.
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D Roland F. Hirsch Charles S.Tuesday
on U.S. Department of Energy General Motors Research Laboratory
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ubli Rudolph J. Marcus Douglas B. Walters
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FOREWORD
The ACS SYMPOSIUM SERIES was founded in 1974 to provide a
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00 medium for publishing symposia quickly in book form. The
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6.f format of the Series parallels that of the continuing ADVANCES
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2 IN CHEMISTRY SERIES except that, in order to save time, the
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6- papers are not typeset but are reproduced as they are submitted
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1 by the authors in camera-ready form. Papers are reviewed under
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1/b the supervision of the Editors with the assistance of the Series
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0 Advisory Board and are selected to maintain the integrity of the
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10. symposia; however, verbatim reproductions of previously pub
oi: lished papers are not accepted. Both reviews and reports of
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6 | research are acceptable, because symposia may embrace both
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PREFACE
INSECT PESTS AND PATHOGENIC FUNGI cause enormous losses of food and
fiber crops throughout the world. These losses tend to obscure the fact that
most plants are resistant to most pests and diseases, and that attack occurs
only when, as a result of coevolution, the pest or parasite has been successful
in overcoming the natural defenses of the host. These defenses may be
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0 morphological. For example, the leaf surface may not be conducive to
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6. feeding or oviposition by the insect or to spore germination or mycelial
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02 growth of the fungus. But, in many cases, the defense mechanism involves
6-
8 the production of endogenous chemicals that deter feeding or oviposition or
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k- inhibit spore germination or mycelial growth.
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1/ Until fairly recently, little was known about the chemical structures of
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1 these endogenous substances. Professor Louis Wain, the keynote speaker of
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oi: 1 the symposium upon which this book is based, pioneered work in this field
d at Wye College in England forty years ago. In the last few years, a surge of
86 | investigations worldwide has resulted in the elucidation of the chemical
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6, 1 structures of many of the endogenous substances that protect plants against
y 1 attack by fungi—the phytoalexins—and in some understanding of the
uar biochemistry of their modes of action. Much work has been done to isolate
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Ja and characterize the endogenous substances that deter insects. It was,
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at therefore, timely to organize this symposium to review the information
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n obtained so far and to consider current research findings and prospects for
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ati the future.
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bli The picture that emerged was a bewildering array of diverse chemicals
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with little, if any, common connection. So far, none of the natural
endogenous chemicals has proved to be useful for crop protection in
practical agriculture because many of the structures are too complex to
permit economical manufacture, and partly because the substances are
produced in nature at or near the site of action, and therefore are not
effective when applied topically. However, a knowledge of the chemical
structures may serve as a guide for the synthesis of analogous compounds
that may be, under appropriate conditions, even more effective than the
natural substances and more economical to manufacture. The feasibility of
this approach is substantiated by the great success that has been achieved in
producing useful agrochemicals based on the structure of the natural
insecticide, pyrethrum, but with much greater utility, higher activity, and
lower cost than the natural substance.
ix
Furthermore, an understanding of the biochemistry, and particularly the
genetic mechanisms of the natural resistance of plants to pests and diseases,
may open up the possibility of transferring this resistance from resistant to
susceptible species. This field has a very exciting future, some idea of which
can be envisaged from the chapters in this volume.
MAURICE B. GREEN
23 Brunswick Road
Withington, Manchester M2O 9QB
England
PAUL A. HEDIN
1 Boll Weevil Research Laboratory
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1
Developing Research Trends in the Chemistry of Plant
Resistance to Pests
Paul A. Hedin
Boll Weevil Research Laboratory, USDA, Agricultural Research Service, Mississippi State,
MS 39762
1
0 The development of crop plant varieties with
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h resistance to insects and diseases has several
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6. advantages compared with other approaches to pest
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02 control because of economics, environmental con
86- siderations, and relative efficiency. In recent
19 years, chemistry has begun to have an impact on
bk- selection of resistant lines. Growing amounts of
21/ information have been synthesized by chemists and
10 cooperating biologists on the presence and roles of
10. allelochemicals in resistant plants, suggesting that
oi: its application to selections may now be a realistic
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6 | strategy. Developing research trends in the che
8 mistry of plant resistance to pests are identified
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1 and reviewed.
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ar The development of crop plant varieties with resistance to pests
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n including insects and diseases has several advantages compared
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e: J with other approaches to pest control. The application of pesti
at cides may be decreased or eliminated, resulting in decreased costs
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n of production and environmental pollution. The use of resistant
atio varieties also does not require the adoption of complicated tech
c nologies by the user.
ubli Until now, resistant varieties have been selected from field
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evaluations by plant breeders, often in cooperation with entomolo
gists, plant pathologists, and/or other biologists. In recent
years, chemists have identified a number of compounds conferring
resistance that had previously or subsequently been shown to be
controlled by single genes or combinations of genes.
Investigations In which a relatively large number of available
susceptible and resistant lines or varieties have been analyzed to
determine whether correlations between the allelochemical and
resistance are statistically significant have only recently been
carried out on a substantive scale. It is therefore generally
accurate to state that the impact of chemistry (and chemists) on
the selection of resistant lines by plant breeders has been mini
mal. On the other hand, the growing amount of information that
This chapter not subject to U.S. copyright.
Published 1986, American Chemical Society
1. HEDIN Developing Research Trends 3
has recently been generated by chemists and cooperating biologists
on the presence ana roles of chemicals in resistant plants
suggests that its application to plant breeding may now be
realistic. Efforts to define the roles of these chemicals in
various plant-insect and plant-plant interactions governing plant
resistance have been reported in a succession of conferences, sym
posia, and their proceedings, especially during the last 10 years
(1-4),
This chapter is an effort to identify the various concepts
and approaches currently being used by scientists to chemically
define the parameters of plant resistance to pests. Of the thir
teen approaches that were identified, only three, each associated
with behavior, were unique to insects. The remaining 10 are
generally applicable to either insects or diseases, and were
therefore not separated. The listing of examples of these may
1 suggest emerging trends which are being successfully followed for
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0 the elucidation of the various chemical bases of plant resistance.
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6.c The examples include not only those presented in this symposium
9 book, but others recently reported.
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98 Origins and Actions of Allelochemicals
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1/ Identification and Roles of Plant Resistance Compounds including
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0 Phytoalexlns. Not all expressions of plant resistance are chemi
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0. cally mediated, but of those that are, the so called secondary
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oi: plant compounds appear to be dominant. Among those shown to
d mediate resistance are the various classes of phenolic compounds
6 | including flavonolds and aromatic acids, terpenoids including the
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19 sesquiterpene lactones and hellocldes, nitrogenous compounds
6, including amino acids and amides, proteinaceous compounds
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y including protease inhibitors, glycosidase inhibitors, and phyto-
uar hemagglutinlns, the lectins, toxic seed lipids including unusual
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a fatty acids, acetylenic and allenic lipids, the fluorolipids and
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e: cyanolipids, the saponins, the tannins, and lignins (1-4). The
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D roles of these compounds are difficult to elucidate for several
on reaeons. Not all compounds toxic to one insect or pathogen are
ati toxic to another. In evolutionary time, some pests have evolved
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Pu plants from which they derive energy and/or other resources
whereas others do not. Also, several resistance mechanisms may be
operative in the plant. To the extent that biosynthesis of these
compounds is an expression of genetic information, the elucidation
of these compounds and their roles can provide a guide to selec
tions by plant breeders. The description in this book of
several polyhydroxyl alkaloids from legumes that act as glycosi
dase inhibitors in insects and other animals (Fellows et al., 5_)
is an unique example. Byers (6) found that 3-nitropropionic acid
from crown vetch was a feeding deterrent, and also toxic to some
insects and non-ruminant animals. Although this compound serves
as a protectant against insects, its decrease or removal could
improve the use of crown vetch as a forage for some animals.
Cutler et al. (7) reported that several diterpenes and sucrose
esters were inhibitory to etiolated wheat coleoptiles and micro
bes, but oviposition stimulants for the tobacco budworm, Hellothis
