Seed Pathology in

Modern Agriculture

Mahendra Nath Khare

Former Professor & Dean

Department ofPlant PathologyJNKWJabalpur 482004

Mohan S. Bhale

Seed Technology Research

Department ofPlant Breeding & Genetics

JNKWJabalpur 482004

AGROBIOS (INDIA)

Contents

1 Significance of Seedborne Microorganisms in

Agriculture, Animal Husbandry and Human Welfare 1

Introduction 1

Role in Agriculture 1

Failure ofGermination 3

Seedling Blight and Rot 3

Disease Symptoms on Adult Plants 3

Association ofPathogens with Seeds 4

Ripening Phase ofthe Seed 4

Weather Condition 4

Species ofPathogen 4

Concomitant Contamination 4

Life Span ofPathogen 5

Type ofCrop and the Pathogen Involved 5

Role in Animal Husbandry 5

Role in Human Welfare 6

Out Breaks ofDiseases of Seedborne Nature 7

History of Seed Pathology 7

Organizations 9

International Seed Testing Association - ISTA 9

Danish Seed Health CentreforDeveloping Countries (DSHC) 10

References 10

2 Characteristics of Quality Seed 11

Basic Seed Testing 12

Physical Purity 12

Seed Viability 13

Germination and Vigour 13

Genetic Purity 14

Seed CultivarIdentification 15

Seed Health 18

Determining Seed Quality 19

Regerences 19

3 Seed Certification 20

Seed Certification 20

Phases ofSeed Certification 21

Seed Certification Procedures 22

Seed Testing 23

Capacity Building and Orientation 24

Organic Certification 24

References 24

4 Procedures for Sampling, Purity Analysis andGermination 25

Prescription 25

Sampling 25

Purity ojSeed 26

Germination Test 27

Germination and Seedling Evaluation 29

Classification ofSeedlings 29

Tetrazolium Testfor Viability 30

Vital Cobring Methods 32

Enzyme ActivityMethods 32

Conductivity Test 32

Excised Embryo Test 32

X-RayTest 32

Evaluation and Interpretation 33

References 33

5 Methods in Seed Health Testing 34

Examination of Seed without Germination or Incubation 34

Examination ofDry Seeds 34

Examination after Softening and Soaking 34

Examination ofSeed Washings 35

Incubation Methods 35

Blotter Method 35

Agar Plate Method 35

Ragdoll Method 35

2,4-D Method 36

Deep Freeze Blotter Method 36

PeptonePCNB Agar 36

Guaiacol Agar Method 36

Incorporation ofFungicides inAgarMedia 36

Growing on Test 37

Hiltner's Brick Stone Method 37

Sand Method 37

Standard Soil Method 37

Use ofother Media 37

Test Tube WaterAgarMethod 37

Cleared Whole Mount 38

References 38

6 Seedborne Fungi 40

Fungal Structures Mixed with the Seed 41

Phycomycetes 41

Ascomycetes 43

Basidio Mycetes 45

Deuteromycetes 51

Phomopsis 52

Other Fungi 69

Epicoccum 69

Nigrospora 69

Pestalotia 70

References 70

7 Seedborne Bacteria 71

Important Genera of Bacteria 71

Xanthomonas 71

Pseudomonas 76

Erwinia 77

Crynebacterium 78

Agrobacterium 78

Mechanism of Seed Infection 80

Survival 80

Dissemination 80

Host Pathogen Interactions 80

Symptomatology 81

Epidemiology 81

Molecular bases ofInteractions between Plant-Pathogenic Bacteria and

Plants 82

Pathways ofTransmission 82

References 83

8 Seedborne Viruses 85

Seedborne Viruses 88

Alfalfa Mosaic Virus (AMY) 88

Barley Stripe Mosaic Virus (BSMV) 89

Bean Common Mosaic Virus (BCMV) and Bean Common Mosaic

Necrosis Virus (BCMNV) 89

Cucumber Mosaic Virus (CMV) 90

Pea Seedborne Mosaic Virus (PSbMV) 91

Broad Bean Stain Virus (BBSV) 91

Cowpea Mild Mottle Carlavirus (CPMMV) 92

Cowpea Aphid-Borne Mosaic Virus (CABMV) 93

Cowpea Severe Mosaic Virus (CpSMV) 93

Southern Bean Mosaic Virus (SBMV) 93

Squash Mosaic Virus (SqMV) 94

Lettuce Mosaic Virus (LMV) 94

Pea Seedborne Mosaic Virus (PSbMV) 95

Bean Yellow Mosaic Virus (BYMV) 96

Pea Enation Mosaic Virus (PEMV) 96

Virus Diseases ofPepper 97

Soybean Mosaic Virus (SMV) 99

Tobacco Ring Spot Virus (TRSV) 99

Tobacco Mosaic Virus (TMV) 100

Tomato Mosaic Virus (ToMV) 101

Virus Transmission 102

Rate ofVirus Transmission through Seed 102

Mechanisms ofTransmission 102

Detection ofViruses, in Seed and Seed Stocks 103

Examination ofDry Seed Prior to Incubation 103

Electrophoresis 105

Serological Test (ELISA) 106

Elimination ofVirus from Seeds 106

References 107

9 Seedborne Nematodes 108

Seedborne Nematodes 109

Aphelenchoides besseyi 109

Anguina tritici 110

Ditylenchus angustus 112

Heterodera rostochiensis 113

Meloidogyne spp 114

References 115

10 Mechanism ofSeed Transmission ofPlant

Pathogens 117

Plant to Seed Infection 117

Infection Directlyfrom the Mother Plant. 118

Injectionfrom Outside US

Physical Environment and the Time ofSeed Infection 120

Infection Time and Flowering Period ofthe Host 120

Infection Time and Localization ofInfection in the Seed 121

Time ofInfection, Weather Conditions and Extent ofSeed Infection 121

Infected or Contaminated Parts of the Seed 122

Ovule Infection 122

Embryo Infection 122

Endosperm Infection 123

Seed Coat and Pericarp Infection 123

Seed Coat and Pericarp Contamination 123

Concomitant Seed Contamination 124

Factors Affecting Transmission of Pathogens from Plant to Seed

and Seed to Plant 124

References 125

11 Seed Health and Storage Conditions 127

Seed Storage 127

Objectives ofSeed Storage 128

Purpose ofSeed Storage 128

Factors Influencing Seed Storage 129

Seed Factors 131

Genetic Factors 131

Abiotic Factors 131

Methods ofSeed Storage 134

Storage at Ambient Temperature and Humidity 134

Dry Storage with Control ofMoisture Content but not Temperature 134

Dry Storage with Control ofBoth Moisture Content and Temperature 134

Dry StorageforLong-Term Gene Conservation 134

Moist Storage without Control ofMoisture Content and Temperature 135

Moist Cold Storage with Control ofTemperature 135

Cryopreservation 135

Storage Containers 136

Factors Affecting Seed Storage 136

Hard Seed 137

Seed Storage Sanitation or Godown Sanitation 138

Maintenance of Viability in Storage 140

Temperature 140

Major Losses to Seeds during Storage 140

Discobration ofSeed or Embryo 140

Reduction in Germination or Loss ofViability 141

Moisture Content ofSeed 141

Storage Temperature 141

Presence ofInsect Fauna 141

Grain Condition 142

Respiration and Heating. 142

Biochemical Changes in Seeds 142

Production ofToxins 142

Loss in Weight 142

Chemical Treatment 143

Benefits ofSeed Treatment 143

Types ofSeed Treatment 143

Conditions under which Seed must be Treated 143

Precautions in Seed Treatment 144

Seed Treatment for Cereal Crops 145

References 145

12 Seed Exudates and Seedborne Microorganisms 146

Chemical Nature of Seed Exudates 146

Factors Affecting Exudation 147

Site ofExudation 147

Seed Exudates vs. Seedborne Microorganisms 147

Methodologyfor Study ofRelease ofSeed Exudatesfrom the

Germinating Seeds 148

Method ofAgrawal and Khare (1974) 149

Method by Nairn et al. (1976) 149

References 150

13 Seed Dormancy 151

Classification ofDormancy 151

The Imposed Dormancy (Quiescence) 151

The Innate (Deep) Dormancy 151

Non Deep Physwbgical Dormancy 152

Intermediate Physiological Dormancy 153

Deep Physiological Dormancy 153

Causes ofDormancy 154

References 156

14 Seed to Plant and Plant to Seed Transmission of

Pathogens and their Management 157

Association of Pathogens with Seed Parts 157

Seed to Plant Transmission ofPathogens 160

Intraembryal Infections 160

Extraembryal Infection 161

Seed Contamination 161

Transmission as Inert Matter 162

Plant to Seed Transmission ofPathogens 162

Management 164

Crop Management 164

Plant to Seed Transmission of Pathogens 168

References 169

15 Seed Legislations Governing Seed Quality IncludingSeed Health 170

Destructive Insects and Pests Act 1914 170

ISTA 170

Seed Testing Laboratory 171

The Seeds Act 1966 171

The Seed Rules, 1968 172

Seed Certification Standards 172

The Seeds (Control) Order, 1983 180

New Policy on Seed Development, 1988 180

National Horticultural Board 180

Plants, Fruits and Seeds (Regulation ofImport into India) Order

1989 (Ministry ofAgriculture, Department ofAgriculture and

Cooperation, New Delhi dated 27* October, 1989) 181

Sanitary and Phytosanitary Measures under WTO 181

Determination ofCry 1AC Gene in Bt Cotton Seed 184

Plant Quarantine (Regulation ofImport into India) (SecondAmendment) Order, 2006 (September 2006pages 1-25) 186

The Seed Bill, 2004 188

The Seed Bitt 2010 188

16 Important Seedborne Diseases ofRice 190

Foot Rot 190

Brown Spot 191

Blast 193

Bacterial Leaf Blight 194

17 Important Seedborne Diseases ofWheat 197

Loose Smut 197

Hill Bunt 199

KarnalBunt 200

Flag Smut 202

Alternaria LeafBlight 204

Foot Rot, Leaf Spot and LeafBlight 205

Ear Cockle 206

Yellow Ear Rot 207

Reference 208

18 Important Seedborne Diseases ofMaize 209

Seedling Blight 209

LeafBlight (Helrninthosporium-LeafBlight) 210

Southern LeafBlight 212

Northern Corn Leaf Spot 214

Stalk and Ear Rot 215

Cephalosporium Ear Rot 217

Downy Mildew 218

19 Important Seedborne Diseases ofSorghum 220

Grain Smut 220

Loose Smut 221

Head Smut 222

Long Smut 222

Ergot 223

LeafBlight 224

Charcoal Rot and Seedling Blight 225

Seed Rot and Seedling Blight 227

Zonate Leaf Spot 228

Other Diseases 229

Black Rot 229

Stalk Rot and Red LeafSpot 229

20 Important Seedborne Diseases of Pearl Millet 230

DownyMildew (Green Ear Disease) 230

Ergot 233

Grain Smut 235

LeafSpots 237

21 Important Seedborne Diseases of Oat 239

LeafSpot and Seedling Blight 239

Covered Smut 240

Loose Smut 241

22 Important Seedborne Diseases ofBarley 243

Covered Smut 243

Loose Smut 245

Root and Foot Rot 246

LeafStripe 248

Barley Mosaic 249

23 Important Seedborne Diseases ofChickpea 251

Ascochyta Blight 251

Wilt 252

Botrytis Gray Mold 253

24 Important Seedborne Diseases ofLentil 255

Fusarium Wilt 255

Seedling Rot 257

Other Diseases 258

LeafBlight 258

Rust 258

Reference 258

25 Important Seedborne Diseases ofBlack Gram 259

Fusarium LeafSpot 259

Leaf Spot 259

Macrophomina Diseases 260

Anthracnose 260

Blight 261

Yellow mosaic (MungbeanYellow Mosaic Virus) 262

Urd Bean Leaf Crinkle 262

Reference 263

26 Important Seedborne Diseases of Greengram 264

Leaf Spot 264

Anthracnose 265

Seed Rot and Seedling Blight 266

Bacterial Leaf Spot 267

Halo Blight 267

Leaf Curl 269

27 Important Seedborne Diseases ofFrench Bean 272

Anthracnose 272

Ashy Stem Blight 273

Angular Leaf Spot 274

Bacterial Leaf Spot and Blight 275

Bean Yellow Mosaic Virus (Bean Common Mosaic Virus) 276

28 Important Seedborne Diseases ofCowpea 277

Anthracnose 277

Bacterial Blight 278

Leaf Spot 279

Dry Root Rot 280

Brown Blotch 280

Charcoal Rot 280

Cow Pea Mosaic (Cow Pea Mosaic Virus) 281

Reference 282

29 Important Seedborne Diseases of Soybean 283

Purple Stain of Seed 283

Charcoal Rot 285

Bacterial Pustule 286

Mosaic (Soybean Mosaic Virus) 287

References 288

30 Important Seedborne Diseases of Peanut 289

Seedling Disease 289

Aspergillus Crown Rot 290

Limb Rot 291

Charcoal Rot 292

Root Rot and Stem Rot 292

Black Hull 292

Aspergillus Blight 293

31 Important Seedborne Diseases ofSunflower 295

Downy Mildew 295

LeafSpot 296

Root Rot 297

"White Rot 299

32 Important Seedborne Diseases of Sesame 301

Root and Stem Rot 301

Bacterial Blight 302

Reference 303

33 Important Seedborne Diseases ofCastor 304

Alternaria Blight 304

Bacterial LeafSpot 305

34 Important Seedborne Diseases ofJute 307

Root and Stem Rot 307

Anthracnose 308

Jute Chlorosis 308

35 Important Seedborne Diseases ofEggplant 310

Phomopsis Blight and Fruit Rot 310

Certification Standards 311

LeafSpot and Fruit Rot 312

Anthracnose 312

36 Important Seedborne Diseases ofTomato 314

Damping Off 314

Seedling Blight 315

Early Blight 315

Buckeye Fruit Rot 317

Phoma Fruit Rot 318

Septoria LeafSpot 320

Bacterial LeafSpot 321

Stem and Fruit Canker 323

37 Important Seedborne Diseases ofCapsicum 325

Damping Off 325

Anthracnose and Die back. 326

Blight and Fruit Rot 328

Bacterial Leaf Spot 329

38 Important Seedborne Diseases of Cauliflower 331

Seed Rot and LeafSpot 331

Black Rot 332

Black Leg 334

Bacterial Soft Rot 335

39 Important Seedborne Diseases of Cabbage 337

LeafSpot and Seedling Blight 337

Black Rot 338

Black Leg 339

40 Important Seedborne Diseases ofPea 340

Leaf, Stem and Pod Spot 340

Powdery Mildew 341

Wilt 342

41 Important Seedborne Diseases ofCarrot 344

LeafBlight and Black Rot 344

Cercospora Blight 345

42 Important Seedborne Diseases ofOkra 347

Seedling Blight 347

Fusarium Blight 347

Pod Spot 347

43 Important Seedborne Diseases ofRadish 348

Seedling Blight and LeafSpot 348

White Rust 348

44 Important Seedborne Diseases ofGuar 350

Seed Rot and Seedling Blight : 350

Seed Rot and Leaf Spot 350

Anthracrose 350

Species Index 351