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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