Plant Disease Control: Towards environmentally acceptable methods

354 Pages·1993·8.81 MB·English

by  Richard N. Strange (auth.)

Plant Disease Control
PLANT DISEASE
CONTROL
Towards environmentally
acceptable methods
Richard N. Strange
Department of Biology
University College London
London UK
D
111
I
SPRINGER-SOENCE+BUSINESS MEDIA, B.V.
First edition 1993
«©~ 1993 Richard N.. Strange
Originally published by Chapman & Hali in 1993
Softcover re print of the hardcover lst edition 1993
Typeset in 10/12pt Times by Columns Design & Production
Services Ltd, Reading
ISBN 978-1-4899-4634-8 ISBN 978-1-4899-4632-4 (eBook)
DOI 10.1007/978-1-4899-4632-4
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The publisher makes no representation, express or implied, with regard to
the accuracy of the information contained in this book and cannot accept any
legal responsibility or liability for any errors or omissions that may be made.
A catalogue record for this book is available from the British Library
Library of Congress Cataloging-in-Publication data available
The cover illustration shows control of papaya ringspot virus by cross
inoculation. Plants on the left are badly infected with the virus; plants on the
right were inoculated with a mild strain of the virus before transplantation, and
are fruiting abundantly. Photographs courtesy of Dr Shyi-Dong Yeh, National
Chung Sing University, Taichung, Taiwan.
To my dear wife, Lilian, and our children, Alison and Julian,
with love and appreciation.
Contents
Preface xi
1 The impact of plant disease on man 1
1.1 Introduction 1
1.2 Diseases causing losses of staple crops 2
1.3 Diseases causing losses of cash crops 13
1.4 Diseases causing losses of ornamental and
environmentally important plants 19
1.5 Diseases causing spoilage of food crops 23
1.6 Summary 27
PART ONE: PARASITE IDENTIFICATION, EPIDEMIOLOGY, DISEASE
MEASUREMENT AND THEIR IMPLICATIONS FOR CONTROL 29
2 Organisms that cause plant disease: their detection,
identification and proof of their role as pathogens 31
2.1 Introduction 31
2.2 Koch's postulates 31
2.3 The range of organisms that cause plant disease 32
2.4 Detection, diagnosis and quantitative assessment of
plant parasites 45
2.5 Summary 60
3 Epidemiology 63
3.1 Introduction 63
3.2 The development of epidemics: theoretical considerations 64
3.3 The role of the pathogen 69
3.4 The role of the host 78
3.5 The role of the environment 78
3.6 Summary 84
viii Contents
4 The measurement of plant disease and its effect on crop yields 85
4.1 Introduction 85
4.2 Parameters of disease and their measurement 86
4.3 Measurement of symptoms 92
4.4 Measurement of yield and quality 97
4.5 Establishing the relation between disease and yield 98
4.6 Summary 104
S Implications of parasite identity, epidemiology and disease
measurement for control measures 107
5.1 Introduction 107
5.2 The importance of control of inoculum 108
5.3 Reducing the sources of inoculum 108
5.4 Reducing inoculum multiplication 116
5.5 Reducing the effectiveness of inoculum in causing disease 117
5.6 The screening, development and application of
biological-control agents 125
5.7 Reducing the spread of inoculum 128
5.8 Summary 135
PART TWO: THE GENETICS AND BIOCHEMISTRY OF HOST-PARASITE
RELATIONS AND THEIR IMPLICATIONS FOR CONTROL 137
6 The genetics of host-parasite interaction 139
6.1 Introduction 139
6.2 Pioneering experiments 140
6.3 The gene-for-gene concept 141
6.4 Other gene-for-gene models 145
6.5 The effects of temperature and genetic background 147
6.6 Corroboration of the gene-for-gene concept by
experiments with transgenic pathogens 149
6.7 Some implications of the gene-for-gene concept 153
6.8 The genetics of pathogenicity and virulence factors 154
6.9 Genes that enable parasites to overcome host
resistance factors 160
6.10 Summary 162
7 Prepenetration and penetration events 163
7.1 Introduction 163
7.2 Chemotaxis 163
7.3 Stimulants of germination and growth of the
propagules of plant parasites 164
7.4 Preparation of the infection court 167
Contents ix
7.5 The formation of infection structures and their role
in establishing infection 168
7.6 Breaching the cell wall 171
7.7 Degradation of lignin 184
7.8 Membranlytic enzymes 184
7.9 Summary 185
8 Toxins 187
8.1 Introduction 187
8.2 Macroscopic symptoms 188
8.3 Bioassay 189
8.4 Structures and modes of action of host-selective toxins 190
8.5 Structures and modes of action of non-host-selective
toxins 198
8.6 Control of toxin biosynthesis 203
8.7 Evaluation of the role of toxins in disease 205
8.8 Summary 206
9 Constitutive barriers to infection 207
9.1 Introduction 207
9.2 Physical barriers to infection 207
9.3 Chemical barriers to infection 208
9.4 Summary 222
10 Induced resistance 225
10.1 Introduction 225
'
10.2 The hypersensitive response 225
10.3 Acquired resistance 226
10.4 Elicitors of defence responses 229
10.5 Phytoalexins 232
10.6 Lignification 242
10.7 Suberization 244
10.8 Hydroxyproline-rich glycoprotein (HRGP) synthesis 244
10.9 Papilla formation and callose deposition 245
10.10 Protein synthesis 246
10.11 Evaluation of the importance of defence mechanisms 247
10.12 Summary 247
11 Symptom expression 249
11.1 Introduction 249
11.2 Auxins 249
11.3 Cytokinins 251
11.4 Gibberellins 253
11.5 Ethylene 254
Contents
X
11.6 Abscisic acid 255
11.7 The role of altered hormone levels in symptom expression 256
11.8 Crown-gall 265
11.9 Summary 269
12 Exploiting knowledge of the genetics and biochemistry of
host-parasite interaction in order to control disease 271
12.1 Introduction 271
12.2 Genetic approaches to the control of plant disease 271
12.3 Control of prepenetration and penetration events 275
12.4 The use of toxins to select for resistance 278
12.5 Exploiting constitutive chemical barriers to infection 280
12.6 Biological control in planta 282
12.7 Amelioration of symptoms 285
12.8 Molecular biology techniques 285
12.9 Summary 290
References 293
Glossary 329
Index 335
Preface
The aim of this book is to provide some basic information about infectious
plant diseases and to focus attention on the development of methods for
controlling them that do not involve the use of broad-spectrum biocidal
chemicals. Although the most effective methods of control are the exclusion
or elimination of the causal parasites, such procedures are frequently not
possible. In these circumstances it becomes important to minimize the
occurrence of the pathogens and to optimize all factors that reduce their
effects on their host plants.
The book is divided into two parts which broadly reflect these two
approaches. In Part One, plant parasites are considered more or less
separately from their hosts. First, the range of organisms that cause disease
is introduced together with methods used for their detection, identification
and proof of their role as pathogens. This is followed by a consideration of
the factors governing epidemics and how diseases and the losses they cause
can be measured. Part One is completed by a discussion of the ways in
which the information given in the previous chapters may be used to derive
control measures.
Part Two is concerned with events that occur after an infectious agent has
arrived in the vicinity of a potential host and the factors that control their
interaction. First, the genetics of host-parasite relations are discussed and
this is followed by two chapters which describe the mechanisms by which
parasites attack plants. Conversely, the next two chapters deal with
mechanisms by which plants resist parasites. Finally, after a discussion of the
means by which symptoms are expressed, the subject matter of the previous
chapters is reviewed from the perspective of developing control methods.
Ignorance concerning the scale and consequences of crop losses caused by
plant disease is generally matched only by the scale of the diseases
themselves. I have therefore included an introductory chapter in which some
examples are given of catastrophic losses and the economic and social
impact that these have had.
Plant pathology is a broad discipline which has, at times, suffered from
over-specialization. One hope I have for the book is that it will bring