PLANT PATHOLOGY. GEORGE N.AGRIOS Department of Plant Pathology University of Florida. twv.-nr.

Transcription

1 Fourth Edition PLANT PATHOLOGY GEORGE N.AGRIOS Department of Plant Pathology University of Florida lechnische Universitat Darmstadt FACHBEREICH 10 BIOLOGIE Bibliothek SchnittspahnstraGe Darmstadt twv.-nr. ACADEMIC PRESS ACADEMIC PRESS A Harcourt Science and Technology Company San Diego San Francisco New York Boston London Sydney Tokyo

2 Contents Preface part xv one GENERAL ASPECTS chapter one INTRODUCTION Plant Pathology: The Science 3 The Concept of Disease in Plants 4 Types of Plant Diseases 4 History of Plant Pathology 7 The Role of Fungi in Plant Disease 10 Discovery of Other Pathogens as Causes of Plant Disease 12 Serious Plant Diseases of Unknown Etiology 13 Early Development of Plant Pathology 13 The Search for Control of Plant Diseases 14 Interest in the Mechanisms by Which Pathogens Cause Disease 17 The Concept of Genetic Inheritance of Resistance and Pathogenicity 18 Epidemiology of Plant Disease Comes of Age 19 Molecular Plant Pathology 19 Development of Plant Pathology Worldwide 20 Trends in Teaching and Training in Plant Pathology 22 Education and Information Technology in Plant Pathology 23 Plant Disease Clinics 23 Plant Pathology: The Practice 23 Certification of Professional Plant Pathologists 25 Significance of Plant Diseases 25 Kinds and Amounts of Losses 25 Some Historical and Present Examples of Losses Caused by Plant Diseases 28 Plant Diseases and World Crop Production 28 Effects of Changes in Agricultural Methods and in Human Society on the Development and Spread of Plant Diseases 34 Basic Procedures in the Diagnosis of Plant Diseases 37 Pathogen or Environment? 37 Infectious Diseases 37 Noninfectious Diseases 39 Identification of a Previously Unknown Disease: Koch's Rules 39 vn

3 Vlll chapter two PARASITISM AND DISEASE DEVELOPMENT Parasitism and Pathogenicity 43 Host Range of Pathogens 44 Development of Disease in Plants 45 Stages in the Development of Disease: The Disease Cycle 45 Inoculation 45 Prepenetration Phenomena 46 Penetration 48 Infection 53 Invasion 54; Growth and reproduction of the pathogen (colonization) 54 Dissemination of the Pathogen 56 Overwintering and/or Oversummering of Pathogens 59 Relationships between Disease Cycles and Epidemics 61 chapter three HOW PATHOGENS ATTACK PLANTS Mechanical Forces Exerted by Pathogens on Host Tissues 63 Chemical Weapons of Pathogens 65 Enzymes in Plant Disease 65 Microbial Toxins in Plant Disease 73 Growth Regulators in Plant Disease 77 Polysaccharides 81 Suppressors of Plant Defense Responses 81 chapter four EFFECTS OF PATHOGENS ON PLANT PHYSIOLOGICAL FUNCTIONS Effects of Pathogens on Photosynthesis 83 Effect of Pathogens on Translocation of Water and Nutrients in the Host Plant 85 Interference with Upward Translocation of Water and Inorganic Nutrients 85 CONTENTS Interference with the Translocation of Organic Nutrients through the Phloem 86 Effect of Pathogens on Host Plant Respiration 87 Respiration of Diseased Plants 88 Effect of Pathogens on Permeability of Cell Membranes 89 Effects of Pathogens on Transcription and Translation 90 Effect on Transcription 90 Effect on Translation 91 chapter five HOW PLANTS DEFEND THEMSELVES AGAINST PATHOGENS Preexisting Structural and Chemical Defenses 93 Preexisting Defense Structures 93 Preexisting Chemical Defenses 94 Induced Structural and Biochemical Defenses 96 Recognition of the Pathogen by the Host Plant 96 Transmission of the Alarm Signal to Host Defense Providers: Signal Transduction 96 Induced Structural Defenses 96 Cytoplasraic defense reaction 97; Cell wall defense structures 97; Histological defense structures 98; Necrotic defense reaction: defense through the hypersensitive response 100 Induced Biochemical Defenses 100 The hypersensitive response 100; Active oxygen radicals, lipoxygenases, and disruption of cell membranes 103; Reinforcement of host cell walls with strengthening molecules 103; Production of antimicrobial substances in attacked host cells 104; Detoxification of pathogen toxins 108; Immunization of plants against pathogens 108; Local and systemic acquired resistance 108; Defense through genetically engineering disease resistant plants 112 chapter six GENETICS OF PLANT DISEASE Introduction 115 Genes and Disease 116

4 CONTENTS IX Variability in Organisms 117 Mechanisms of Variability 118 General Mechanisms of Variability 118 Specialized Mechanisms of Variability in Pathogens 119 Stages of Variation in Pathogens 121 Types of Plant Resistance to Pathogens 122 True Resistance 122 Apparent Resistance 124 Genetics of Virulence in Pathogens and of Resistance in Host Plants 125 The Gene-for-Gene Concept 126 The Nature of Resistance to Disease 128 Genetics of Resistance through the Hypersensitive Response 129 Breeding of Resistant Varieties 135 Natural Variability in Plants 135 Effects of Plant Breeding on Variability in Plants 135 Plant Breeding for Disease Resistance 136 chapter seven ENVIRONMENTAL EFFECTS ON THE DEVELOPMENT OF INFECTIOUS PLANT DISEASE Effect of Temperature 144 Effect of Moisture 146 Effect of Wind 148 Effect of Light 149 Effect of Soil ph and Soil Structure 149 Effect of Host-Plant Nutrition 149 Effect of Herbicides 151 chapter eight PLANT DISEASE EPIDEMIOLOGY The Elements of an Epidemic 153 Host Factors That Affect the Development of Epidemics 155 Pathogen Factors That Affect Development of Epidemics 156 Environmental Factors That Affect Development of Epidemics 158 Effect of Human Cultural Practices and Control Measures 158 Measurement of Plant Disease and of Yield Loss 159 Patterns of Epidemics 160 Comparison of Epidemics 162 Development of Epidemics 163 Modeling of Plant Disease Epidemics 165 Computer Simulation of Epidemics 166 Forecasting Plant Disease Epidemics 167 Assessment of Initial Inoculum and of Disease 167 Monitoring Weather Factors That Affect Disease Development 167 Examples of Plant Disease Forecast Systems 168 Disease-Warning Systems 170 Development and Use of Expert Systems in Plant Pathology 171 chapter nine CONTROL OF PLANT DISEASES Control Methods That Exclude the Pathogen from the Host 174 Quarantines and Inspections 174 Evasion or Avoidance of Pathogen 175 Use of Pathogen-Free Propagating Material 175 Control Methods That Eradicate or Reduce Pathogen Inoculum 177 Cultural Methods That Eradicate or Reduce the Inoculum 178 Biological Methods That Eradicate or Reduce the Inoculum 181 Physical Methods That Eradicate or Reduce the Inoculum 188 Chemical Methods That Eradicate or Reduce the Inoculum 190 Disease Control by Immunizing, or Improving the Resistance of, the Host 192 Cross Protection 193 Induced Resistance: Systemic Acquired Resistance 193 Plant Defense Activators 193 Improving the Growing Conditions of Plants 194 Use of Resistant Varieties 194 Direct Protection of Plants from Pathogens 195

5 CONTENTS Direct Protection by Biological Controls 195 Fungal antagonists 196; Bacterial antagonists 197 Biological Control of Weeds 199 Direct Protection by Chemical Controls 200 Methods of application of chemicals for plant disease control 203; Types of chemicals used for plant disease control 208; Inorganic chemicals used for plant disease control 208; Organic chemicals: contact protective fungicides 209; Organic compounds: systemic fungicides 210; Miscellaneous organic fungicides 212; Antibiotics 212; Plant oils and petroleum oils 213; Growth regulators 213; Nematicides 213; Mechanisms of action of chemicals used to control plant diseases 214; Resistance of pathogens to chemicals 215; Restrictions on chemical control of plant diseases 216 Integrated Control of Plant Diseases 216 Integrated Control in a Perennial Crop 217 Integrated Control in an Annual Crop 218 part two SPECIFIC PLANT DISEASES chapter ten ENVIRONMENTAL FACTORS THAT CAUSE PLANT DISEASES Introduction 225 General Characteristics 225 Diagnosis 225 Control 226 Temperature Effects 226 High-Temperature Effects 227 Low-Temperature Effects 228 Low-Temperature Effects on Indoor Plants 228 Mechanisms of Low- and High-Temperature Injury to Plants 230 Moisture Effects 230 Low Soil Moisture Effects 230 Low Relative Humidity Effects 231 High Soil Moisture Effects 231 Inadequate Oxygen 232 Light 232 Air Pollution 233 Air Pollutants and Kinds of Injury to Plants 233 Main Sources of Air Pollutants 234 How Air Pollutants Affect Plants 234 Acid Rain 236 Nutritional Deficiencies in Plants 236 Soil Minerals Toxic to Plants 238 Herbicide Injury 240 Other Improper Agricultural Practices 241 The Often Confused Etiology of Stress Diseases 242 chapter eleven PLANT DISEASE CAUSED BY FUNGI Introduction 245 Characteristics of Plant Pathogenic Fungi 245 Morphology 245 Reproduction 246 Ecology 246 Dissemination 248 Classification of Plant Pathogenic Fungi 248 Fungallike Organisms or Pseudofungi 248 The True Fungi 249 Identification 254 Symptoms Caused by Fungi on Plants 254 Isolation of Fungi (and Bacteria) 255 Preparing for Isolation 255 Isolating the Pathogen 257 Life Cycles of Fungi 258 Control of Fungal Diseases of Plants 259 Diseases Caused by Fungallike Organisms 260 Diseases Caused by Myxomycota (Myxomycetes) 260 Diseases Caused by Plasmodiophoromycetes 263 Clubroot of crucifers 263 Diseases Caused by the Chromistan Fungallike Oomycetes 266 Pythium Seed Rot, Damping-off, Root Rot, and Soft Rot 266

6 CONTENTS XI Phytophthora Diseases 270 Phytophthora root and stem rots 270; potatoes 274 The Downy Mildews 2 78 Downy mildew of grape 280 Diseases Caused by True Fungi 283 Diseases Caused by Chytridiomycota (Chytridiomycetes) 283 Late blight of Diseases Caused by Zygomycetes 283 Rhizopus soft rot of fruits and vegetables 285 Diseases Caused by Ascomycetes and Imperfect (Asexual) Fungi 286 Sooty Molds 289 Leaf Curl Diseases Caused by Taphrina 293 The Powdery Mildews 295 Powdery mildew of rose 297 Foliar Diseases Caused by Ascomycetes and Imperfect Fungi 298 Alternaria diseases 300; Rice blast disease 303; Black rot of grape 304; Needle casts and blights of conifers 304; Mycosphaerella diseases 307; Banana leaf spot, or Sigatoka disease 307; Cucurbit gummy stem blight 307; Cerospora diseases 309; Septoria diseases 310; Cochliobolus and Pyrenophora diseases of cereals and grasses 310 Stem and Twig Cankers Caused by Ascomycetes and Imperfect Fungi 317 Dothichiza canker of poplar 318; Black knot of plum and cherry 319; Chestnut blight 319; Nectria canker 319; Leucostoma canker 321 Anthracnose Diseases Caused by Ascomycetes and Imperfect Fungi 324 Black spot of rose 324; Glomerella diseases 325; Gnomonia anthracnose and leaf spot diseases 328; Colletotrichum (Gloeosporium) diseases 329 Fruit and General Diseases Caused by Ascomycetes and Imperfect Fungi 331 Ergot of cereals and grasses 332; Apple scab 334; Brown rot of stone fruits 336; Botrytis diseases 339 Vascular Wilts Caused by Ascomycetes and Imperfect Fungi 342 Fusarium wilts 343; Fusarium wilt of tomato 343; Vertidllium wilts 346; Ophiostoma (Ceratocystis) wilt of elm trees: Dutch elm disease 346 Root and Stem Rots Caused by Ascomycetes and Imperfect Fungi 350 Gibberella diseases 351; Fusarium root and stem rots of nongrain crops 352; Take-all of wheat 354; Sclerotinia diseases 355; Phymatotrichum root rot 358 Postharvest Diseases of Plant Products Caused by Ascomycetes and Imperfect Fungi 359 Postharvest decays of fruits and vegetables 361; Alternaria 361; Botrytis 362;. Fusarium, Geotrichum, Penicillium, Sclerotinia 363; Control of postharvest decays of fresh fruits and vegetables 364; Postharvest decays of grain and legume seeds 364; Mycotoxins and mycotoxicoses 365; Aflatoxins 365; Fusarium toxins 366; Other Aspergillus toxins and Penicillium toxins 366 Diseases Caused by Basidiomycetes 368 The Rusts 368 Cereal rusts 371; Stem rust of wheat and other cereals 371; Cedar-apple rust 375; Coffee rust 375; Rusts of forest trees 377; White pine blister rust 378; Fusiform rust 380 The Smuts 382 Corn smut 382; Kernel smuts of small grains 384; Loose smut of cereals 384; Covered smut, or bunt, of wheat 387 Root and Stem Rots Caused by Basidiomycetes 389 Root and stem rot diseases caused by the "sterile fungi" Rhizoctonia and Sclerotium 390; Rhizoctonia diseases 390; Sclerotium diseases 395; Root rots of trees 397; Armillaria root rot of fruit and forest trees 397 Wood Rots and Decays Caused by Basidiomycetes 399 Mycorrhizae 404 Ectomycorrhizae 404; Endomycorrhizae 404 chapter twelve PLANT DISEASES CAUSED BY PROKARYOTES: BACTERIA AND MOLLICUTES Introduction 407 Plant Diseases Caused by Bacteria 408 Characteristics of Plant Pathogenic Bacteria 409 Morphology 409 Reproduction 411 Ecology and Spread 412 Identification of Bacteria 412 Symptoms Caused by Bacteria 415 Control of Bacterial Diseases of Plants 415

7 Xll CONTENTS Bacterial Spots and Blights 416 Wildfire of tobacco 417; Bacterial blights of bean 418; Angular leaf spot of cucumber 419; Angular leaf spot of cotton 420; Bacterial leaf spots and blights of cereals and grasses 421; Bacterial spot of tomato and pepper 421; Bacterial speck of tomato 422; Bacterial spot of stone fruits 422 Bacterial Vascular Wilts 423 Bacterial wilt of cucurbits 424; Fire blight of pear and apple 426; Ring rot of potato 429; Bacterial canker and wilt of tomato 430; Southern bacterial wilt of solanaceous plants and Moko disease of banana 431; Black rot of crucifers 433 Bacterial Soft Rots 434 Bacterial soft rots of vegetables 435 Bacterial Galls 438 Crown gall 438 Bacterial Cankers 441 Bacterial canker and gummosis of stone fruit trees 442; Citrus canker 445 Bacterial Scabs 449 Common scab of potato 449 Root Nodules of Legumes 451 Plant Diseases Caused by Fastidious Vascular Bacteria 453 Pierce's disease of grape 455; Citrus variegated chlorosis 456; Ratoon stunting of sugarcane 456 Plant Diseases Caused by Mollicutes: Phytoplasmas and Spiroplasmas 457 Properties of True Mycoplasmas 457 Phytoplasmas 458 Spiroplasmas 460 Other Organisms That Resemble Mollicutes: L-Forms of Bacteria 462 Examples of Plant Diseases Caused by Mollicutes 462 Aster yellows 462; Lethal yellowing of coconut palms 464; Elm yellows (phloem necrosis) 465; Peach X-disease 465; Pear decline 467; Citrus stubborn disease 467; Corn stunt disease 469 chapter thirteen PLANT DISEASES CAUSED BY PARASITIC HIGHER PLANTS Introduction 471 Dodder 471 Witchweed 473 Broomrapes 475 Dwarf Mistletoes of Conifers, 475 True or Leafy Mistletoes 477 chapter fourteen PLANT DISEASES CAUSED BY VIRUSES Introduction 479 Characteristics of Plant Viruses 479 Detection 480 Morphology 480 Composition and Structure 480 Satellite Viruses and Satellite RNAs 484 The Biological Function of Viral Components: Coding 485 Virus Infection and Virus Synthesis 485 Translocation and Distribution of Viruses in Plants 488 Symptoms Caused by Plant Viruses 489 Physiology of Virus-Infected Plants 491 Transmission of Plant Viruses 491 Transmission of Viruses by Vegetative Propagation 492 Mechanical Transmission of Viruses through Sap 492 Seed Transmission 494 Pollen Transmission 494 Insect Transmission 494 Mite Transmission 495 Nematode Transmission 495 Fungus Transmission 496 Dodder Transmission 496 Epidemiology of Plant Viruses and Viroids 496 Purification of Plant Viruses 497 Serology of Plant Viruses 497 Nomenclature and Classification of Plant Viruses 500 Detection and Identification of Plant Viruses 503 Economic Importance of Plant Viruses 505 Control of Plant Viruses 505 Diseases Caused by Rigid Rod-Shaped Viruses 508

8 CONTENTS Xlll Diseases Caused by Tobamoviruses: Tobacco Mosaic Virus 508 Diseases Caused by Tobraviruses 510 Diseases Caused by Furoviruses 510 Diseases Caused by Hordeiviruses 511 Diseases Caused by Filamentous Viruses 512 Diseases Caused by Potexviruses 512 Diseases Caused by Carlaviruses 512 Diseases Caused by Capilloviruses and Trichoviruses' 512 Diseases Caused by Potyviridae 513 Diseases Caused by Potyviruses 513 Bean common mosaic and bean yellow mosaic 515; Lettuce mosaic 515; Papaya ringspot 516; Plum pox 517; Potato virus Y 517; Sugarcane mosaic 518; Tobacco etch 518; Turnip mosaic 519; Watermelon mosaic 519; Zucchini yellow mosaic 519 Diseases Caused by Rymoviruses and Bymoviruses 519 Diseases Caused by Closteroviruses 519 Beet yellows 519; Citrus tristeza 519; Lettuce infectious yellows 521 Diseases Caused by Isometric Single-Stranded RNA Viruses 523 Diseases Caused by Waikaviruses 523 Rice tungro 523; Maize chlorotic dwarf 525 Diseases Caused by Luteoviruses 525 Beet western yellows 525; Potato leafroll 525; Barley yellow dwarf 525 Diseases Caused by Comoviridae 527 Diseases Caused by Comoviruses 527 Diseases Caused by Nepoviruses 528 Tomato ring spot 528; Cherry leaf roll 528; Grapevine fanleaf 529; Raspberry yellow dwarf, raspberry ring spot, and raspberry leaf curl 529 Diseases Caused by Bromoviridae 530 Diseases Caused by Cucumoviruses 530 Cucumber mosaic 531 Diseases Caused by Ilarviruses 532 Prunus necrotic ring spot 533 Diseases Caused by Isometric Double-Stranded RNA Viruses 534 Diseases Caused by Reoviridae 536 Diseases Caused by Negative RNA [(-)ssrna] Viruses 538 Plant Diseases Caused by Rhabdoviruses 538 Plant Diseases Caused by Tospoviruses 539 Plant Diseases Caused by Tenuiviruses 541 Diseases Caused by Double-Stranded DNA Viruses 545 Diseases Caused by Caulimoviruses 545 Diseases Caused by Badnaviruses 546 Diseases Caused by Single-Stranded DNA Viruses 547 Plant Diseases Caused by Geminiviruses 547 Maize streak 551; Beet curly top r 551; African cassava mosaic 551; Bean golden mosaic 552; Squash leaf curl 553; Tomato mottle 553; Tomato yellow leaf curl 554 Plant Diseases Caused by Isometric Single- Stranded DNA Viruses 554 Banana bunchy top 555 Viroids 556 Plant Diseases Caused by Viroids 556 Potato spindle tuber 560; Citrus exocortis 560; Coconut cadang-cadang 561 chapter fifteen PLANT DISEASES CAUSED BY NEMATODES Introduction 565 Characteristics of Plant Pathogenic Nematodes 565 Morphology 565 Anatomy 565 Life Cycles 566 Ecology and Spread 566 Classification 568 Isolation of Nematodes 569 Isolation of Nematodes from Soil 569 Isolation of Nematodes from Plant Material 570 Symptoms Caused by Nematodes 571 How Nematodes Affect Plants 571 Interrelationships between Nematodes and Other Plant Pathogens 572 Control of Nematodes 573 Root-Knot Nematodes: Meloidogyne 574 Cyst Nematodes: Heterodera and Globodera 511 Soybean cyst nematode: Heterodera glycines 577; Sugar beet nematode: Heterodera schachtii 579

9 XIV CONTENTS The Citrus Nematode: Tylencbulus chapter sixteen semipenetrans 581 p LANT DISEASES CAUSED BY Lesion Nematodes: Pratylenchus 581 The Burrowing Nematode: Radopholus 583 FLAGELLATE PROTOZOA Stem and Bulb Nematode: Ditylenchus 586 Introduction 599 Seed-Gall Nematodes: Anguina 588 Phloem Necrosis of Coffee 601 Foliar Nematodes: Aphelenchoides 590 Hartrot of Coconut Palms 604 Pine Wilt and Palm Red Ring Diseases: Sudden Wilt (Marchitez) of Oil Palm 604 Bursaphelenchus, 592 Empty Root of Cassava 605 Pine wilt nematode: Bursaphelenchus xylophilus 592; Red ring nematode: Bursaphelencus cocophilus 593 Stubbly-Root Nematodes: Paratrichodorus Glossary 607 and Trichodorus 596 Index 619