Table Of ContentF i f t h E d i t i o n
PLANT
PATHOLOGY
F i f t h E d i t i o n
PLANT
PATHOLOGY
GEORGE N. AGRIOS
Department of Plant Pathology
University of Florida
Amsterdam • Boston • Heidelberg • London • New York • Oxford
Paris • San Diego • San Francisco • Singapore • Sydney • Tokyo
Publisher Dana Dreibelbis
Associate Acquisitions Editor Kelly D. Sonnack
Project Manager Troy Lilly
Marketing Manager Linda Beattie
Cover Design Eric DeCicco
Composition SNP Best-set Typesetter Ltd., Hong Kong
Cover Printer RR Donnelley & Sons Company
Interior Printer RR Donnelley & Sons Company
Elsevier Academic Press
30 Corporate Drive, Suite 400, Burlington, MA 01803, USA
525 B Street, Suite 1900, San Diego, California 92101-4495, USA
84 Theobald’s Road, London WC1X 8RR, UK
This book is printed on acid-free paper.
Copyright © 2005, 1997, 1988, 1978, 1969 Elsevier Inc. All rights reserved.
No part of this publication may be reproduced or transmitted in any form or by
any means, electronic or mechanical, including photocopy, recording, or any
information storage and retrieval system, without permission in writing from the
publisher.
Permissions may be sought directly from Elsevier’s Science & Technology Rights
Department in Oxford, UK: phone: (+44) 1865 843830, fax: (+44) 1865 853333,
e-mail: [email protected]. You may also complete your request on-line
via the Elsevier homepage (http://elsevier.com), by selecting “Customer Support”
and then “Obtaining Permissions.”
Library of Congress Cataloging-in-Publication Data
Agrios, George N., 1936–
Plant pathology / George Agrios.—5th ed.
p. cm.
Includes bibliographical references and index.
ISBN 0-12-044565-4 (hardcover: alk. paper)
1. Plant diseases. I. Title.
SB731.A35 2004
571.9¢2—dc22
2004011924
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
For all information on all Elsevier Academic Press Publications
visit our Web site at www.books.elsevier.com
Printed in the United States of America
04 05 06 07 08 09 9 8 7 6 5 4 3 2 1
This, the 5th and probably the last edition of Plant Pathology by me, is dedicated:
To the memory of my parents, Nikolas and Olga, who, in spite of their limited
education, sacrificed everything to give me the most and best education possible.
To the memory of Dr. Walter F. Buchholtz, my major professor at Iowa State
University, who challenged me before I had even taught my first lecture to “write
my own textbook on Plant Pathology”.
To my sisters, Dimitra and Evangelia, who have been there for me forever and who
also sacrificed some of their interests for my benefit.
To my wife, Annette, whose love and support have been the most precious things to
me throughout our life together, and who helped me in many facets of preparation of
this and of previous editions of Plant Pathology.
To my daughters-in-law, Betsy and Vivynne, who, by joining our family, added beauty,
love, enjoyment, and four wonderful grandchildren.
Finally, to Mark and Maximos, our youngest grandchildren, who, someday, when
they read their names in the book, may be reassured of “Granpa’s” love for them,
and may feel proud of their grandfather.
C o n t e n t s
Preface xxi The Expanding Role of Fungi as Causes of Plant
Photo credits xxiii Disease 21
About the Author xxvi The Discovery of the Other Causes of Infectious
Diseases 23
part one Nematodes 23; Protozoan Myxomycetes 24;
Bacteria 24; Viruses Protozoa 25;
Mollicutes 26; Viroids 26; Serious Plant
GENERAL ASPECTS
Diseases of Unknown Etiology 26; Koch’s
Postulates 26; Viruses, Viroids, and Prions 27
Losses Caused by Plant Diseases 29
chapter one Plant diseases reduce the quantity and quality of
plant produce 29
INTRODUCTION
White, Downey, and Dry Vineyards—Bring on the
Prologue: The Issues 4 Bordeaux! 30
Plants and Disease 4 Plant diseases may limit the kinds of plants and
The Concept of Disease in Plants 5 industries in an area 32
Types of Plant Diseases 7 Familiar trees in the landscape: going, going, gone
History of Plant Pathology and Early (Box) 32
Chestnuts, Elms, and Coconut Palm Trees—Where have
Significant Plant Diseases 8
they gone? 32–35
Introduction 8
Plant diseases may make plants poisonous to
Plant Diseases as the Wrath of Gods—Theophrastus
humans and animals 37
(Box) 9; Mistletoe Recognized as the First Plant
Ergot, Ergotism, and LSD: a Bad Combination (Box) 37;
Pathogen (Box) 14; Plant Diseases as the Result of
Mycotoxins and Mycotoxicoses (Box) 39
Spontaneous Generation (Box) 16; Biology and
Plant Pathology in Early Renaissance (Box) 16; Plant diseases may cause financial losses 41
Potato Blight—Deadly Mix of Ignorance and Politics The Insect—Pathogen Connection: Multifaceted and
(Box) 19 Important (Box) 42
vii
viii CONTENTS
Plant Pathology in the 20th Century 45 Identification of a Preciously Unknown Disease:
Early Developments 45 Koch’s Postulates 74
The Descriptive Phase 45; The Experimental
Phase 46; The Etiological Phase 46; The Search
chapter two
for Control of Plant Diseases 46
The Main Areas of Progress 47 PARASITISM AND DISEASE
Chemical Control of Plant Diseases 47; Appearance DEVELOPMENT
of Pathogen Races Resistant to Bactericides and
Parasitism and Pathogenicity 77
Fungicides 48; Public Concern about Chemical
Pesticides 48; Alternative Controls for Plant Host Range of Pathogens 78
Diseases 49; Interest in the Mechanisms by Which Development of Disease in Plants 79
Pathogens Cause Disease 50; The Concept of
Stages in the Development of Disease:
Genetic Inheritance of Resistance and Pathogenicity 52;
The Disease Cycle 80
Epidemiology of Plant Disease Comes of Age 53
Plant Pathology Today and Future Inoculation 80
Inoculation 80; Types of Inoculum 80; Sources of
Directions 54
Inoculum 80; Landing or Arrival of Inoculum 81
Molecular Plant Pathology 54
Prepenetration Phenomena 82
Aspects of Applied Plant Pathology 56
Attachment of Pathogen to Host 82; Spore
Plant Biotechnology—The Promise and the Objections
Germination and Perception of the Host Surface 82;
(Box) 56; Food Safety (Box) 58; Bioterrorism,
Appressorium Formation and Maturation 85;
Agroterrorism, Biological Warfare, etc. Who, What,
Recognition between Host and Pathogen 86;
Why (Box) 59
Germination of Spores and Seeds 86; Hatching of
Worldwide Development of Plant Pathology as Nematode Eggs 87
a Profession 60 Penetration 87
International Centers for Agricultural Research 60; Direct Penetration through Intact Plant Surfaces 87;
Trends in Teaching and Training 61; Plant Disease Penetration through Wounds 88; Penetration
Clinics 62; The Practice and Practitioners of Plant through Natural Openings 88
Pathology 63; Certification of Professional Plant Infection 89
Pathologists 63; Plant Pathology as a Part of Plant
Infection 89; Invasion 91; Growth and
Medicine; the Doctor of Plant Medicine Program
Reproduction of the Pathogen (Colonization) 91
(Box) 64
Dissemination of the Pathogen 96
Plant Pathology’s Contribution to Crops
Dissemination by Air 96; Dissemination by Water 97;
and Society 65 Dissemination by Insects, Mites, Nematodes, and Other
Some Historical and Present Examples of Losses Vectors 97; Dissemination by Pollen, Seed,
Transplants, Budwood, and Nursery Stock 100;
Caused by Plant Diseases 65
Dissemination by Humans 100
Plant Diseases and World Crop Production 65
Overwintering and/or Oversummering of
Crop Losses to Diseases, Insects and
Pathogens 100
Weeds 66
Relationships between Disease Cycles and
Pesticides and Plant Diseases 69
Epidemics 102
Basic Procedures in the Diagnosis of Plant
Diseases 71
chapter three
Pathogen or Environment 71
EFFECTS OF PATHOGENS ON PLANT
Infectious Diseases 72
Parasitic Higher Plants 72; Nematodes 72; Fungi PHYSIOLOGICAL FUNCTIONS
and Bacteria: Fungi 72; Bacteria and
Effects of Pathogens on Photosynthesis 106
Mollicutes 72; Viruses and Viroids 73; More
than One Pathogen 73 Effect of Pathogens on Translocation of Water
Noninfectious Diseases 73 and Nutrients in the Host Plant 106
CONTENTS ix
Interference with Upward Translocation of Water Apparent Resistance 137
and Inorganic Nutrients 106 Disease Escape 137; Tolerance to Disease 139
Genetics of Virulence in Pathogens and of
Effect on Absorption of Water by Roots 108
Resistance in Host Plants 139
Effect on Translocation of Water through
the Xylem 108 The Nature of Resistance to Disease 142
Effect on Transpiration 108 Pathogenicity Genes in Plant Pathogens 142
Genes Involved in Pathogenesis and Virulence by
Interference with the Translocation of Organic
Pathogens 142
Nutrients through the Phloem 113
Pathogenicity Genes of Fungi controlling:
Effect of Pathogens on Host Plant
Production of Infection Structures 144
Respiration 115
Degradation of Cuticle and Cell Wall 144
Respiration of Diseased Plants 117
Secondary Metabolites 145
Effect of Pathogens on Permeability of Cell
Fungal Toxins 146
Membranes 118
Pathogenicity Signaling Systems 146
Effects of Pathogens on Transcription and
Pathogenicity Genes in Plant Pathogenic
Translation 118
Bacteria 146
Effect on Transcription 119; Effect on
Translation 119 Bacterial Adhesion to Plant Surfaces 146
Effect of Pathogens on Plant Growth 119 Secretion Systems 147
Effect of Pathogens on Plant Enzymes that Degrade Cell Walls 147
Reproduction 121 Bacterial Toxins as Pathogenicity Factors 148
Extracellular Polysaccharides as Pathogenicity
Factors 148
chapter four
Bacterial Regulatory Systems and
GENETICS OF PLANT DISEASE
Networks 148
Introduction 125 Sensing Plant Signaling Components 149
Genes and Disease 126 Other Bacterial Pathogenicity Factors 149
Variability in Organisms 128 Pathogenicity Genes in Plant Viruses 149
Mechanisms of Variability 128 Functions Associated with the Coat Protein 149
General Mechanisms: Mutation 129; Viral Pathogenicity Genes 150
Recombination 129; Gene and Genotype Flow
Nematode Pathogenicity Genes 150
among Plant Pathogens 130; Population Genetics,
Genetics of Resistance through the Hypersensitive
Genetic Drift, and Selection 130; Life Cycles —
Reproduction — Mating Systems — Out- Response 151
crossing 131; Pathogen Fitness 131; Specialized Pathogen-Derived Elicitors of Defense Responses in
Mechanisms of Variability in Pathogens 131; Plants 151; Avirulence (avr) Genes: One of the
Sexual-like Processes in Fungi Heterokaryosis 131; Elicitors of Plant Defense Responses 151;
Parasexualism 132; Vegetative Characteristics of avr Gene-Coded Proteins 153;
Incompatibility 132; Heteroploidy 132; Their Structure and Function Role of avrGenes in
Sexual-like Processes in Bacteria and Horizontal Pathogenicity and Virulence 154; hrpGenes and the
Gene Transfer 132; Genetic Recombination in Type III Secretion System 155
Viruses 133; Loss of Pathogen Virulence in Resistance (R) Genes of Plants 155
Culture 133
Examples of R Genes 156
Stages of Variation in Pathogens 134
How Do R Genes Confer Resistance? 157
Types of Plant Resistance to Pathogens 134
Evolution of R Genes 157
True Resistance: Partial, Quantitative, Polygenic, or
Other Plant Genes for Resistance to
Horizontal Resistance—R-Gene Resistance,
Monogenic, or Vertical Resistance 136 Disease 158
