Soilborne Microbial Plant Pathogens and Disease Management, Volume Two
Management of Crop Diseases

Crop disease management strategies revolve around the principles of exclusion, eradication and immunization. Cultural practices are aimed at preventing or reducing the accumulation of pathogen population (inoculum). Development of cultivars with genetic resistance by transgressing resistance gene(s) through traditional breeding procedures or biotechnological techniques is the most effective and acceptable strategy, as it is environment-friendly and does not need any additional cost to the grower. Assessment of different grades of resistance of cultivars or genotypes to soilborne microbial pathogens has been possible by quantifying pathogen populations or their DNA contents in the test plants by applying biological and molecular methods.

This second volume of a two-volume set focuses on the soilborne microbial plant pathogens and the diseases caused by them. The book provides information on ecology and epidemiology of soilborne microbial plant pathogens and various strategies applicable for effective management of diseases. Chapters cover exclusion and prevention strategies; improvement of host plant resistance; biological management; application of chemicals; and integration of these disease management strategies.

Features

• Discusses various aspects of soilborne microbial plant pathogens to develop effective methods of managing diseases.
• Presents information on epidemiology and ecology of soilborne microbial plant pathogens.
• Facilitates the application of management strategies alone or in combination with others for effective suppression of disease development.
• Features information on application of biotic and abiotic biological control agents (BCAs) to suppress pathogen development either by directly acting on the pathogen(s) or indirectly by enhancing host resistance to the pathogens.
• Employs biotic and abiotic biocontrol agents either to replace or reduce the use of chemicals is an achievable approach for managing the soilborne microbial pathogens.

Contents

Preface.......................................................................................................................................................................................... xi

Acknowledgment........................................................................................................................................................................xiii

Author.......................................................................................................................................................................................... xv

Chapter 1 Management of Soilborne Microbial Plant Pathogens – Exclusion and Prevention Strategies............................... 1

1.1 Exclusion of Microbial Plant Pathogens........................................................................................................ 1

1.1.1 Use of Disease-Free Seeds and Propagules..................................................................................... 1

1.1.2 Prevention of Pathogen Entry through Plant Quarantines............................................................... 2

1.1.3 Impact of Introduced Microbial Plant Pathogens............................................................................ 3

1.1.3.1 Potato Late Blight Disease............................................................................................... 3

1.1.3.2 Banana Fusarium Wilt Disease........................................................................................ 3

1.1.3.3 Potato Virus Diseases....................................................................................................... 4

1.1.4 Removal of Infected Plant Tissues................................................................................................... 4

1.2 Soil Health Management............................................................................................................................... 4

1.2.1 Cultural Practices............................................................................................................................. 5

1.2.1.1 Disposal of Infected Plants and Residues......................................................................... 5

1.2.1.2 Tillage Practices............................................................................................................... 5

1.2.1.3 Propagation Practices....................................................................................................... 7

1.2.1.4 Date of Planting/Sowing and Planting Density................................................................ 8

1.2.1.5 Canopy Management Practices........................................................................................ 9

1.2.1.6 Irrigation Practices......................................................................................................... 10

1.2.1.7 Crop Nutrition................................................................................................................. 12

1.2.1.8 Effects of Other Crops.................................................................................................... 21

1.3 Physical Techniques.................................................................................................................................... 28

1.3.1 Heat Treatments............................................................................................................................. 28

1.3.2 Radiation Treatments..................................................................................................................... 31

1.4 Chemical Techniques.................................................................................................................................. 31

1.4.1 Treatment of Irrigation Water........................................................................................................ 31

1.4.2 Treatment of Soil............................................................................................................................ 32

1.4.3 Treatment of Tools.......................................................................................................................... 32

References.............................................................................................................................................................. 32

Chapter 2 Management of Soilborne Microbial Plant Pathogens: Improvement of Host Plant Resistance........................... 39

2.1 Types of Disease Resistance........................................................................................................................ 39

2.1.1 Vertical Resistance......................................................................................................................... 39

2.1.2 Horizontal Resistance.................................................................................................................... 40

2.2 Host Plant Resistance to Soilborne Fungal Pathogens................................................................................ 41

2.2.1 Genetic Basis of Disease Resistance.............................................................................................. 41

2.2.1.1 Screening for Disease Resistance................................................................................... 41

2.2.2 Mechanisms of Resistance to Fungal Pathogens........................................................................... 73

2.2.2.1 Gene-for-Gene Interactions in Plant Host–Pathogen Systems....................................... 75

2.2.2.2 Nonhost Resistance to Fungal Pathogens....................................................................... 80

2.2.2.3 Enhancement of Resistance through Rootstocks............................................................ 81

2.2.2.4 Plant Defense Mechanisms............................................................................................. 82

2.3 Host Plant Resistance to Soilborne Bacterial Pathogens............................................................................. 95

2.3.1 Genetic Basis of Resistance to Bacterial Pathogens...................................................................... 95

2.3.1.1 Screening for Resistance to Bacterial Pathogens........................................................... 95

2.3.2 Mechanisms of Resistance to Bacterial Pathogens........................................................................ 99

2.4 Host Plant Resistance to Soilborne Viral Pathogens................................................................................. 103

2.4.1 Genetic Basis of Resistance to Viruses........................................................................................ 104

2.4.2 Mechanisms of Resistance to Soilborne Viruses......................................................................... 109

2.5 Transgenic Resistance to Soilborne Microbial Pathogens.........................................................................110

2.5.1 Transgenic Resistance to Fungal Pathogens.................................................................................111

2.5.1.1 Employing Genes from Wild Relatives for Transformation..........................................111

2.5.1.2 Targeting Structural Components of Fungal Pathogens................................................112

2.5.1.3 Employing Genes Expressing Antifungal Proteins.......................................................114

2.5.1.4 Use of Genes for Modifying Host Plant Metabolism....................................................115

2.5.2 Transgenic Resistance to Bacterial Pathogens..............................................................................116

2.5.2.1 Transfer of Genes from Nonhost Plants........................................................................116

2.5.2.2 Use of Genes Encoding Antibacterial Proteins of Diverse Origin................................116

2.5.3 Transgenic Resistance to Viral Pathogens....................................................................................117

2.5.3.1 Pathogen-Derived Resistance........................................................................................117

References.............................................................................................................................................................119

Chapter 3 Management of Soilborne Microbial Plan Pathogens: Biological Management of Crop Diseases..................... 135

3.1 Assessment of Biological Control Potential of Biotic Agents................................................................... 135

3.1.1 Fungal Biological Control Agents................................................................................................ 135

3.1.1.1 Assessment of Biocontrol Potential of Fungal Isolates................................................ 136

3.1.2 Mycorrhizal Biological Control Agents....................................................................................... 145

3.1.2.1 Assessment of Biological Control Potential................................................................. 146

3.1.3 Bacterial Biological Control Agents............................................................................................ 149

3.1.3.1 Assessment of Biological Control Potential of Bacterial Isolates................................ 150

3.1.4 Viral Biological Control Agents................................................................................................... 159

3.1.4.1 Viruses Infecting Fungal Pathogens............................................................................. 159

3.1.4.2 Viruses Infecting Bacterial Pathogens......................................................................... 160

3.1.4.3 Cross-Protection with Mild Strains of Plant Viruses................................................... 162

3.1.5 Mechanisms of Action of Biotic Biocontrol Agents.................................................................... 162

3.1.5.1 Fungal Biological Control Agents................................................................................ 162

3.1.5.2 Bacterial Biological Control Agents..............................................................................173

3.1.6 Formulations of Biological Products............................................................................................ 183

3.1.6.1 Development of Formulations...................................................................................... 183

3.2 Assessment of Biocontrol Potential of Abiotic Agents............................................................................. 187

3.2.1 Natural Products of Plant and Animal Origin............................................................................. 187

3.2.1.1 Effects of Composts...................................................................................................... 187

3.2.1.2 Effects of Plant Residues...............................................................................................191

3.2.1.3 Effects of Plant Products.............................................................................................. 193

3.2.1.4 Effects of Animal Products.......................................................................................... 194

3.2.2 Synthetic Organic Compounds.................................................................................................... 196

3.2.2.1 Salicylic Acid................................................................................................................ 196

3.2.2.2 Benzothiadiazole.......................................................................................................... 197

3.2.2.3 s-Aminobutyric Acid.................................................................................................... 198

3.2.2.4 Glycerol......................................................................................................................... 199

3.2.2.5 Ethanol.......................................................................................................................... 199

3.2.3 Inorganic Chemicals.................................................................................................................... 199

References............................................................................................................................................................ 201

Chapter 4 Management of Soilborne Microbial Plant Pathogens: Chemical Application....................................................217

4.1 Assessment of Activity of Chemicals Against Fungal Pathogens..............................................................217

4.1.1 Laboratory Tests............................................................................................................................218

4.1.1.1 Agar-Amended Assay....................................................................................................218

4.1.1.2 Microbioassay............................................................................................................... 221

4.1.1.3 Colorimetric Bioassay................................................................................................... 221

4.1.1.4 Nanoparticles Assay..................................................................................................... 221

4.1.2 Methods of Application of Chemicals......................................................................................... 222

4.1.2.1 Treatment of Seeds/Propagules.................................................................................... 222

4.1.2.2 Treatment of Aerial Plant Organs................................................................................. 224

4.1.2.3 Pre-Plant Dip Treatment of Crowns/Roots................................................................... 227

4.1.2.4 Treatment of Soil.......................................................................................................... 227

4.1.2.5 Fungicide Application Based on Weather-Based Advisories....................................... 232

4.1.2.6 Dissipation Dynamics of Fungicides............................................................................ 232

4.1.3 Resistance of Fungal Pathogens to Fungicides............................................................................ 234

4.1.3.1 In Vitro Assessment of Fungicide Resistance.............................................................. 235

4.1.3.2 Greenhouse Assessment of Fungicide Resistance in Pathogens..................................240

4.1.3.3 Field Assessment of Fungicide Resistance in Pathogens..............................................240

4.1.3.4 Distribution of Pathogen Isolates Resistant to Fungicides........................................... 241

4.1.3.5 Fungicide Resistance Induced by Mutation in Fungal Pathogens................................ 241

4.1.3.6 Molecular Characterization and Mechanisms of Fungicide Resistance...................... 243

4.1.3.7 Inheritance of Resistance to Fungicides.......................................................................244

4.1.4 Mechanisms of Action of Fungicides........................................................................................... 245

4.1.5 Effects of Chemical Application on Nontarget Organisms......................................................... 249

4.2 Assessment of Activities of Chemicals Against Bacterial Pathogens....................................................... 249

4.2.1 Use of Disinfectants..................................................................................................................... 249

4.2.2 Use of Bactericides....................................................................................................................... 250

References............................................................................................................................................................ 250

Chapter 5 Management of Soilborne Microbial Plant Pathogens: Development of Integrated

Disease Management Systems............................................................................................................................. 257

5.1 Components of Integrated Disease Management Systems........................................................................ 257

5.2 Management of Diseases of Agricultural Crops....................................................................................... 258

5.2.1 Wheat Diseases............................................................................................................................ 258

5.2.1.1 Wheat-Take-All Disease............................................................................................... 258

5.2.1.2 Rhizoctonia Bare Patch Disease................................................................................... 259

5.2.2 Rice Sheath Blight Disease.......................................................................................................... 259

5.2.3 Cotton Diseases............................................................................................................................ 260

5.2.3.1 Verticillium Wilt Disease............................................................................................. 260

5.2.3.2 Seedling Diseases......................................................................................................... 260

5.2.3.3 Root Rot Disease.......................................................................................................... 261

5.2.4 Soybean Diseases......................................................................................................................... 261

5.2.4.1 Damping-Off/Root Rot Disease................................................................................... 261

5.2.4.2 Sclerotinia Stem Rot Disease........................................................................................ 261

5.2.5 Chickpea Diseases........................................................................................................................ 261

5.2.5.1 Fusarium Wilt Disease................................................................................................. 261

5.2.5.2 Ascochyta Blight Disease............................................................................................. 262

5.2.5.3 Damping-Off Disease................................................................................................... 262

5.2.6 Peanut Diseases............................................................................................................................ 262

5.2.6.1 Root Rot Disease.......................................................................................................... 262

5.2.6.2 Sclerotinia Stem Blight Disease................................................................................... 263

5.2.6.3 Stem Rot Disease.......................................................................................................... 263

5.2.6.4 Collar Rot Disease........................................................................................................ 264

5.2.7 Canola Diseases........................................................................................................................... 264

5.2.7.1 Sclerotinia Stem Rot Disease........................................................................................ 264

5.2.7.2 Rhizoctonia Root Rot Disease...................................................................................... 264

5.2.7.3 Blackleg Disease........................................................................................................... 264

5.2.7.4 Clubroot disease........................................................................................................... 264

5.3 Management of Diseases of Horticultural Crops...................................................................................... 265

5.3.1 Tomato Diseases........................................................................................................................... 265

5.3.1.1 Damping-Off Diseases................................................................................................. 265

5.3.1.2 Fusarium Wilt Disease................................................................................................. 265

5.3.1.3 Late Blight Disease....................................................................................................... 266

5.3.1.4 Bacterial Wilt Disease.................................................................................................. 266

5.3.2 Potato Diseases............................................................................................................................. 267

5.3.2.1 Late Blight and Tuber Blight Disease........................................................................... 267

5.3.2.2 Verticillium Wilt Disease............................................................................................. 267

5.3.2.3 Stem Canker and Black Scurf Disease......................................................................... 267

5.3.2.4 Scab Diseases............................................................................................................... 268

5.3.2.5 Blackleg and Soft Rot Disease...................................................................................... 268

5.3.3 Pepper Diseases............................................................................................................................ 268

5.3.3.1 Verticillium Wilt Disease............................................................................................. 268

5.3.3.2 Crown and Root Rot Disease........................................................................................ 268

5.3.4 Cucurbit Fusarium Wilt Disease.................................................................................................. 268

5.3.5 Allium White Rot Disease........................................................................................................... 269

5.3.6 Sugar Beet Root and Crown Rot Disease..................................................................................... 269

5.3.7 Cabbage Diseases......................................................................................................................... 269

5.3.7.1 Yellows Disease............................................................................................................ 269

5.3.7.2 Damping-Off Disease................................................................................................... 270

5.3.7.3 Clubroot Disease........................................................................................................... 270

5.3.8 Lettuce Diseases........................................................................................................................... 270

5.3.8.1 Sclerotinia Rot Disease................................................................................................. 270

5.2.8.2 Verticillium Wilt Disease............................................................................................. 270

5.3.9 Banana Panama (Fusarium) Wilt Disease................................................................................... 270

5.3.10 Strawberry Diseases..................................................................................................................... 271

5.3.11 Tobacco Diseases......................................................................................................................... 272

5.3.11.1 Black Rot Disease......................................................................................................... 272

5.3.11.2 Black Shank Disease.................................................................................................... 272

References............................................................................................................................................................ 272

Index.......................................................................................................................................................................................... 277

Prof. P. Narayanasamy was awarded the B.Sc.(Ag.) (1958), M.Sc.(Ag.) (1960), and Ph.D. (1963) degrees by the University of Madras and later the Rockefeller Foundation Fellowship to pursue Postdoctoral research on Rice Virus diseases at the International Rice Research Institute, Philippines during 1966 – 1967. He served as the Virus Pathologist at the Indian Agricultural Research Institute, New Delhi during 1969 – 1970. He returned to his Alma Mater which was upgraded as the Tamil Nadu Agricultural University (TNAU), Coimbatore in 1971. He was appointed as the Associate Professor and promoted later as the Professor and Head of the Department of Plant Pathology. He was elected as the Fellow of Indian Phytopathological Society, New Delhi. He functioned as the Editor of the Madras Agricultural Journal published from the Tamil Nadu Agricultural University Campus and as member of editorial committees of the Plant Pathology Journals published in India. He was invited to participate as the lead speaker and chairman of sessions in the National Seminars held in India.

As a researcher in Plant Pathology, he was the leader of the projects on diseases of rice, legumes and oilseeds. He organized the National Seminar for the Management of Diseases of Oilseed Crops. His research on antiviral principles yielded practical solutions for the management of virus diseases affecting various crops. He published over 200 research papers in national and international journals. He was the Principal Investigator of several research projects funded by the Department of Science and Technology, Government of India, New Delhi and the International Crops Research Institute for Semi-Arid Tropics, Hyderabad, India. He continues to share his experience and knowledge with the staff and graduate students of the Department of Plant Pathology, TNAU, Coimbatore. As a teacher, he taught courses on Plant Virology, Molecular Biology, Physiopathology, and Crop disease management for