Horticultural Nematology

N.G. Ravichandra

Horticultural Nematology

ISBN 978-81-322-1840-1 ISBN 978-81-322-1841-8 (eBook) DOI 10.1007/978-81-322-1841-8 Springer New Delhi Heidelberg New York Dordrecht London

Library of Congress Control Number: 2014934835

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N.G. Ravichandra Professor and Scheme Head, AICRP (Nematodes)Department of Plant Pathology University of Agricultural Sciences Bangalore, Karnataka , India

Dedicated to My Mother

vii

Horticulture is an integral and important component in an agrarian economy like India. Horticultural crops constitute a signifi cant segment of the total agricultural production of the nation. The importance of horticulture in improving the productivity of land, generating employment, improving economic conditions of the farmers and entrepreneurs, enhancing exports, and, above all, providing nutritional security to the people is widely acknowl-edged. Horticulture has and will always exist as a matrix of interrelated areas with overlapping and complex relationships. Describing its importance in the physiological, psychological, and social activities of people is the key to expanding understanding of horticulture.

Controlling phytonematodes is of great economic importance, when it comes to successful cultivation of horticultural crops cultivated either in open fi elds or polyhouse conditions. Worldwide, they cause signifi cant damage and yield loss. The paradox is that much of the loss can be prevented with a little care. There is clearly a lot that needs to be done to expand our knowl-edge on plant-parasitic nematodes and our ability to deal with them.

These “hidden enemies” are diffi cult to manage as they are soilborne and their populations vary mainly with soil type, soil moisture/temperature, and genotype. Complex diseases involving nematodes and other soilborne fungi and bacteria complicate the problem. Most insidiously, phytonematodes evolve, often overcoming the resistance that is many a time hard-earned achievement of the plant breeder. Major horticultural crops worldwide are subject to nematode attack in the nursery, fi eld, protected cultivation, or even during postharvest stage, which affects both the quantity and quality of the produce, resulting in loss to the grower.

The book entitled Horticultural Nematology authored by Dr. N.G. Ravichandra is an attempt to provide a detailed information on nematodes of important horticultural crops and their management. The book is written with the objective of providing a comprehensive and latest information on phyto-nematodes. An exclusive chapter on novel methods of managing phytonema-todes in horticulture without dealing with usual nematode management practices provides a new dimension to nematode management using latest, novel molecules. The book also throws light on the potential and future novel nematode management strategies.

I congratulate the author Dr. N.G. Ravichandra, Nematologist, AICRP (Nematodes), Department of Plant Pathology, Agricultural College,

Foreword

viii

University of Agricultural Sciences, GKVK campus, Bangalore, Karnataka, India, for providing details of essential topics pertaining to phytonematodes associated with horticultural crops. I am sure that its readers will fi nd it very useful and informative.

Bangalore

12 Jan 2014 Director of Research

Foreword

ix

Recent advances have shown that horticulture could become an environmen-tally benign technology. Horticulture causes much less degradation of the natural resources than agriculture. It is well known that phytonematodes are of major concern to a wide range of horticultural crops grown worldwide, which cause suffi cient crop damage and severe loss in the yield. Plant- parasitic nematodes pose an enormous problem for global horticultural security. In the fi rst instance, there is a lack of complete knowledge on precise identity/ diagnosis of strains of few damaging nematode pathogens that currently exist. Potentially most dangerous phytonematodes are genetically variable, which stands as a warning that genetic uniformity of even a small part of the genome of a widely grown crop risks the hazard of a major epidemic of a nematode with the ability to exploit the trait(s) that it governs.

However, detailed and latest information on major aspects of phytonema-todes associated exclusively with horticultural crops is lacking. Hence, it was thought to present a comprehensive book that covers some major nematode topics of relevance to horticulture. The purpose of this book is to highlight the signifi cance of phytonematodes in horticulture. It also provides basic informa-tion on plant-parasitic nematodes since it is required for a better understanding of advanced topics. Several popular topics, information on which is already available in plenty, have been avoided. Thus, this book explicates both the essential fundamental and advanced aspects pertaining to nematodes associ-ated with horticultural crops.

The book is conveniently divided into 13 chapters, which cover the latest information on the major fundamental and advanced aspects related to phyto-nematodes including the role of phytonematodes in horticultural industry, phylogenetic and evolutionary concepts in nematodes, major phytonema-todes associated with horticultural crops and their diagnostic keys, symptoms caused by phytonematodes and disease diagnosis, nematode population threshold levels, crop loss assessment, nematode diseases of horticultural crops and their management, nematode disease complexes, genetics of nema-tode parasitism, important nematological techniques, and nematodes of quar-antine importance. One chapter in particular can be singled out for special comment. An exclusive chapter on novel methods of nematode management has been included mainly to provide information on the latest molecules and novel modes of managing nematodes attacking horticultural crops. Routine nematode management aspects, information on which is already available,

Pref ace

x

have not been discussed; instead, this topic refl ects the changing scenario of future nematode management.

This comprehensive book can serve as a friendly guide to meet the require-ments of the students, teachers, and researchers interested in these “hidden enemies” of the grower, apart from the research and extension personnel working under public organizations, offi cials of state departments of horticul-ture and forestry, fi eld workers, and all those concerned and working with plant-parasitic nematodes. Appropriate diagrams, convincing tables, and suit-able graphs/illustrations have been furnished at the right places. A bibliogra-phy providing the list of references cited has also been included at the end.

The author appreciates receiving suggestions and constructive criticism that would improve the quality of the book (e-mail: ravichandrang_3@yahoo.co.in).

Bangalore, Karnataka, India N. G. Ravichandra2014

Preface

xi

I am grateful to Dr. M. A. Shankar, Director of Research, University of Agricultural Sciences, Bangalore, Karnataka, India, who was kind enough to write the foreword for this book, which I greatly acknowledge with thanks.

My sincere thanks to Dr. K. Narayana Gowda, Hon’ble Vice Chancellor, University of Agricultural Sciences, Bangalore, for his support.

I extend my thanks to Dr. R. K. Jain, Project Coordinator, AICRP (Nematodes), and Dr. (Mrs.) A. L. Umarao, Principal Scientist and Head, Division of Nematology, Indian Agricultural Research Institute, New Delhi, India, for their encouragement and concern. My special thanks to Dr. B. N. Sathyanarayana, Professor and Head, Department of Horticulture, UAS, GKVK, Bangalore, for his moral support.

I acknowledge with thanks the assistance rendered by Prof. B. M. R. Reddy, Professor and University Head; Dr. T. Narendrappa, Professor and Head; the faculty of the Department of Plant Pathology, UAS, GKVK, Bangalore; and Mr. B. R. Nagendra, AICRP (Nematodes).

I would like to express my deep sense of gratitude to my beloved parents Sri. N. Gurushankaraiah and Smt. Parvathamma to whom I affectionately dedicate this book.

I wish to record my appreciation and affectionate thanks to my wife Deepthi and daughter Anusha for their affection, patience, keen interest, and follow-up throughout the preparation of the manuscript. Mere words fail to acknowledge their support and cooperation. I am grateful to my in-laws for their encouragement.

I remain ever grateful to my brother-in-law Sudesh Kumar and sister Tara for their special care, affection, and moral support. I fondly acknowledge their keen interest and continued encouragement being showered on me.

I also take this opportunity to thank M/s. Springers Publications, New Delhi, for their help in processing the manuscript and getting the book published.

Acknowledgment

xiii

1 Horticulture and Its Role in the National Economies ................ 1

2 Phytonematodes: Threat to Horticulture.................................... 5 2.1 Ten Economically Important Genera of Phytonematodes

Associated with Horticultural Crops .................................. 9 2.2 Less Widely Distributed Phytonematodes ......................... 11 2.3 General Characteristics of Phytonematodes ...................... 12 2.3.1 Body Size ......................................................... 13 2.3.2 Body Shape ...................................................... 13 2.3.3 Reproduction in Nematodes ............................. 13 2.3.4 Males ................................................................ 13 2.3.5 Females ............................................................ 14 2.3.6 Major Types of Reproduction .......................... 14 2.4 Common Names of Major Phytonematodes

of Horticultural Crops .......................................................... 15 References ....................................................................................... 16

3 Phylogenetic and Evolutionary Concepts in Nematodes ........... 17 3.1 Nematode Relationships to Other Animals ........................ 18 3.2 Phylogenetic Concept ........................................................ 19 3.3 Criteria for Inferring Phylogenetic Tree ............................ 20 3.4 Common Terminologies Used ........................................... 24 3.5 Features Shared by Nematoda with Related Groups ......... 24 3.6 Unique Features to Nematoda ............................................ 25 3.7 Evolutionary Trends of Nematoda ..................................... 27 3.8 Morphological Characters of Nematode in the Light

of Evolution........................................................................ 28 3.9 Evolutionary Concepts ....................................................... 29 3.10 Evolutionary Relationships of Root-Knot Nematodes....... 30 3.11 Nematode Genome Evolution ............................................ 32 3.12 The Range of Genome Size Across the Nematoda ............ 33 3.12.1 Genome Size and Gene Count ......................... 34 3.13 Ancient Linkage Groups .................................................... 35 3.14 The Nematode HOX Gene Cluster .................................... 36 3.15 Evolution of X and Y Chromosomes in Nematodes .......... 37 3.16 Evolution of Gene Content ................................................ 40 3.17 Proliferation and Loss of Gene Families ........................... 41 3.18 Species-Specifi c Genes ...................................................... 42

Contents

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3.19 Horizontal Gene Transfer in the Nematoda ....................... 42 3.20 Identifying Parasitism Genes ............................................. 43 3.21 Phylogeny and Introns ....................................................... 44 3.22 Intron Losses ...................................................................... 45 3.23 Changes in Splice Donor Sites ........................................... 46 3.24 Evolution of Parasitism in Nematodes ............................... 48 3.24.1 Mode and Tempo of the Evolution

of Parasitism ..................................................... 48 3.25 Nematode Mating Systems and Evolution ......................... 49 References ....................................................................................... 50

4 Major Phytonematodes Associated with Horticultural Crops and Their Diagnostic Keys ................................................ 55

4.1 Potato Rot Nematode ( Ditylenchus destructor ) ................. 55 4.1.1 Scientifi c Classifi cation .................................... 55 4.2 Stem and Bulb Nematode ( Ditylenchus dipsaci ) ............... 56 4.2.1 Scientifi c Classifi cation .................................... 56 4.3 Awl Nematode ( Dolichodorus spp.) .................................. 57 4.3.1 Scientifi c Classifi cation .................................... 57 4.4 Golden Cyst Nematode of Potato

( Globodera rostochiensis ) .................................................. 58 4.4.1 Scientifi c Classifi cation .................................... 58 4.5 Pale Cyst Nematode of Potato ( Globodera pallida ) .......... 60 4.5.1 Scientifi c Classifi cation .................................... 60 4.6 Spiral Nematode ( Helicotylenchus spp.) ............................ 63 4.6.1 Scientifi c Classifi cation .................................... 63 4.7 Sheath Nematode ( Hemicycliophora thienemanni ) ........... 63 4.7.1 Scientifi c Classifi cation .................................... 63 4.8 Sugar Beet Cyst Nematode ( Heterodera schachtii ) ........... 64 4.8.1 Scientifi c Classifi cation .................................... 64 4.9 Lance Nematode ( Hoplolaimus gaelatus ) ......................... 65 4.9.1 Scientifi c Classifi cation .................................... 65 4.10 Needle Nematode ( Longidorus spp.) ................................. 66 4.10.1 Scientifi c Classifi cation .................................... 66 4.11 Southern Root-Knot Nematode

( Meloidogyne incognita ) .................................................... 67 4.11.1 Scientifi c Classifi cation .................................... 67 4.12 Javanese Root-Knot Nematode

( Meloidogyne javanica ) ..................................................... 68 4.12.1 Scientifi c Classifi cation .................................... 68 4.13 Peanut Root-Knot Nematode

( Meloidogyne arenaria ) ..................................................... 69 4.13.1 Scientifi c Classifi cation .................................... 69 4.14 Northern Root-Knot Nematode

( Meloidogyne hapla ) .......................................................... 70 4.14.1 Scientifi c Classifi cation .................................... 71 4.15 False Root-Knot Nematode ( Nacobbus spp.) .................... 71 4.15.1 Scientifi c Classifi cation .................................... 71 4.16 Stubby-Root Nematode ( Trichodorus spp.) ....................... 72 4.16.1 Scientifi c Classifi cation .................................... 72

Contents

xv

4.17 Pin Nematode ( Paratylenchus spp.) ................................... 73 4.17.1 Scientifi c Classifi cation .................................... 73 4.18 Lesion Nematode ( Pratylenchus coffeae ) .......................... 74 4.18.1 Scientifi c Classifi cation .................................... 74 4.19 Burrowing Nematode ( Radopholus similis ) ....................... 75 4.19.1 Scientifi c Classifi cation .................................... 75 4.20 Reniform Nematode ( Rotylenchulus reniformis ) ............... 75 4.20.1 Scientifi c Classifi cation .................................... 76 4.21 Yam Nematode ( Scutellonema spp.) .................................. 76 4.21.1 Scientifi c Classifi cation .................................... 76 4.22 Stunt Nematode ( Tylenchorhynchus spp.).......................... 77 4.22.1 Scientifi c Classifi cation .................................... 77 4.23 Dagger Nematode ( Xiphinema americanum ) .................... 78 4.23.1 Scientifi c Classifi cation .................................... 78 4.24 Strawberry Foliar Nematode

( Aphelenchoides fragariae ) ................................................ 78 4.24.1 Scientifi c Classifi cation .................................... 78 4.25 Chrysanthemum Foliar Nematode

( Aphelenchoides ritzemabosi ) ............................................ 79 4.25.1 Scientifi c Classifi cation .................................... 79 4.26 Mushroom Nematode ( Aphelenchoides composticola ) ..... 80 4.26.1 Scientifi c Classifi cation .................................... 80 4.27 Mushroom Spawn Nematode

( Ditylenchus myceliophagu s) ............................................. 80 4.27.1 Scientifi c Classifi cation .................................... 80 4.28 Bent Grass Nematode/Purple Nematode

( Anguina agrostis ) .............................................................. 81 4.28.1 Scientifi c Classifi cation .................................... 81 4.29 Sting Nematode ( Belonolaimus longicaudatus ) ................ 82 4.29.1 Scientifi c Classifi cation .................................... 82 4.30 Coconut Red Ring Nematode or Palm Nematode

( Rhadinaphelenchus/Bursaphelenchus cocophilus ) .......... 82 4.30.1 Scientifi c Classifi cation .................................... 83 4.31 Ring Nematode ( Criconema spp.) ..................................... 84 4.31.1 Scientifi c Classifi cation .................................... 84 4.32 Ring Nematode ( Criconemoides spp.) ............................... 85 4.32.1 Scientifi c Classifi cation .................................... 85 4.33 A Summarized Diagnostic Key to Major Genera

of Phytonematodes ............................................................. 86 References ....................................................................................... 88

5 Symptoms Caused by Phytonematodes and Disease Diagnosis ................................................................... 89

5.1 Damage .............................................................................. 89 5.2 General Aboveground Symptoms ...................................... 91 5.3 Abnormalities Resulting from Injury to Buds,

Growing Points, and Flower Primordia ............................. 92 5.3.1 Dead or Devitalized Buds ................................ 92 5.3.2 Crinkled and Distorted Stems

and Foliage/“Crimp” ........................................ 93 5.3.3 Seed Galls ........................................................ 93

Contents

xvi

5.4 Abnormalities Resulting from Internal Injury to Stems and Foliage .......................................................... 93

5.4.1 Necrosis and Discoloration .............................. 93 5.4.2 Leaf Spots and Lesions .................................... 94 5.4.3 Leaf Galls ......................................................... 94 5.4.4 Twisting of Leaves and Stem ........................... 94 5.4.5 Crinkled and Distorted Stem and Foliage ........ 95 5.5 Symptoms Due to Belowground Feeders........................... 95 5.5.1 Symptoms on Aboveground Plant Parts .......... 95 5.6 Symptoms on Belowground Plant Parts ............................. 96 5.6.1 Root Galls/Root Knots ..................................... 96 5.6.2 Rhizobium Nodules/Nematode Galls ............... 97 5.6.3 Other Root Swellings ....................................... 97 5.6.4 Rotting of Fleshy Parts ..................................... 97 5.6.5 Surface Necrosis .............................................. 98 5.6.6 Lesions ............................................................. 98 5.6.7 Excessive Root Branching ............................... 98 5.6.8 Injured/Reduced/Devitalized Root Tips ........... 99 5.6.9 Abbreviated Root Systems ............................... 99 Reference ........................................................................................ 100

6 Nematode Population Threshold Levels ..................................... 101 6.1 Threshold Levels ................................................................ 101 6.1.1 Pathogens ......................................................... 105 6.1.2 Soil Type .......................................................... 105 6.1.3 Vigor ................................................................ 106 6.1.4 Antagonism ...................................................... 106 6.1.5 Temperature ..................................................... 106 6.2 Population Dynamics ......................................................... 107 6.2.1 Synergy ............................................................ 110 6.2.2 Sampling .......................................................... 111 6.2.3 Extraction ......................................................... 111 6.2.4 Host .................................................................. 111 6.3 Economic Threshold Based on Initial Nematode

Population (Pi) ................................................................... 112 6.3.1 Population Change over Time .......................... 113 6.3.2 Economics ........................................................ 113 References ....................................................................................... 113

7 Crop Loss Assessment .................................................................. 115 7.1 Crop Losses Due to Nematodes ......................................... 115 7.2 Sampling for Nematodes .................................................... 116 7.3 Damage by Nematodes ...................................................... 117 7.3.1 Components of Damage ................................... 117 7.3.2 Mechanical Disturbance ................................... 117 7.3.3 Physiological Disturbance ............................... 117 7.3.4 Molecular Events ............................................. 118 7.3.5 Mechanisms of Interactions ............................. 119 7.3.6 Damage Models ............................................... 119 7.3.7 Mechanisms of Damage and Environmental

Effects on Damage ........................................... 121 7.3.8 Methods of Estimating Yield Losses ............... 123

Contents

xvii

7.4 Types of Interactions .......................................................... 124 7.4.1 Quantifying Nematode Stress .......................... 125 7.5 Distributional Aspects ........................................................ 125 References ....................................................................................... 126

8 Nematode Diseases of Horticultural Crops ................................ 127 8.1 Fruit Crops ......................................................................... 127 8.1.1 Banana .............................................................. 127 8.1.2 Citrus ................................................................ 132 8.1.3 Grapes .............................................................. 135 8.1.4 Papaya .............................................................. 138 8.1.5 Strawberry ........................................................ 139 8.2 Temperate Fruits ................................................................ 142 8.2.1 Apple ................................................................ 142 8.2.2 Peach ................................................................ 143 8.2.3 Plum ................................................................. 144 8.3 Tree Fruits and Small Fruits ............................................... 145 8.3.1 Cherry .............................................................. 145 8.4 Vegetable Crops ................................................................. 147 8.4.1 Economic Loss ................................................. 147 8.4.2 Major Nematode Parasites of Vegetables ......... 147 8.4.3 Endoparasitic Plant-Parasitic Nematodes ........ 148 8.4.4 Ectoparasitic Nematodes .................................. 152 8.5 Onion and Garlic ................................................................ 157 8.5.1 Major Symptoms .............................................. 157 8.5.2 Onion ................................................................ 157 8.6 Sugar Beet .......................................................................... 159 8.6.1 Symptoms and Damage ................................... 159 8.6.2 Management ..................................................... 159 8.7 Medicinal and Aromatic Plants .......................................... 160 8.7.1 Mints ( Mentha spp.) ......................................... 160 8.7.2 Basils ( Ocimum spp.) ....................................... 160 8.7.3 Henbane ( Hyoscyamus sp.) .............................. 162 8.7.4 Davana ( Artemisia pallens ) .............................. 162 8.7.5 Yam ( Dioscorea spp.) ...................................... 162 8.7.6 Patchouli ( Pogostemon cablin, P. patchouli ) ... 163 8.7.7 Geranium ( Pelargonium graveolens ) ............... 164 8.7.8 Coleus ( C. forskohlii, C. aromaticus ) .............. 164 8.7.9 Vanilla ( V. planifolia ) ....................................... 165 8.8 Ornamental Crops .............................................................. 165 8.8.1 General Symptoms ........................................... 165 8.8.2 Crossandra ( Crossandra undulaefolia L.) ........ 167 8.8.3 Tuberose ( Polianthes tuberosa ) ........................ 168 8.8.4 Chrysanthemum ( Chrysanthemum spp.) .......... 169 8.8.5 Rose ( Rosa spp.) .............................................. 170 8.8.6 Gladiolus ( Gladiolus spp.) ............................... 170 8.8.7 Jasmine ( Jasminum spp.) ................................. 171 8.8.8 Carnation ( Dianthus caryophyllus )

and Gerbera ( Gerbera jamesonii ) .................... 171 8.8.9 Tulips ( Tulipa spp.) .......................................... 172 8.8.10 Lilies ( Lilium spp.) ........................................... 172 8.8.11 Dahlia ( Dahlia spp.) ......................................... 172 8.8.12 China Aster ( Callistephus chinensis ) ............... 172

Contents

xviii

8.9 Plantation Crops ................................................................. 172 8.9.1 Coconut ( Cocos nucifera ) ................................ 172 8.9.2 Areca Nut ( Areca catechu ) ............................... 175 8.9.3 Coffee ( Coffea arabica, C. canephora ) ........... 175 8.9.4 Tea ( Camellia sinensis ) .................................... 176 8.9.5 Betel Vine ( Piper betle L.) ............................... 177 8.9.6 Cocoa ( Theobroma cacao L.) .......................... 179 8.10 Spices and Condiments ...................................................... 179 8.10.1 Black Pepper ( Piper nigrum L.) ....................... 179 8.10.2 Cardamom ( Elettaria cardamomum ) ............... 181 8.10.3 Ginger ( Zingiber offi cinale ) ............................. 182 8.10.4 Turmeric ( Curcuma longa ) .............................. 183 8.10.5 Other Spices ..................................................... 184 8.11 Tuber Crops ........................................................................ 184 8.11.1 Sweet Potato ( Ipomea batatus ) ........................ 184 8.11.2 Yam ( Dioscorea alata ) ..................................... 184 8.11.3 Cassava ( Manihot esculenta ) ........................... 185 8.11.4 Colocasia ( Colocasia esculenta ) ...................... 186 8.12 Polyhouse Crops/Crops Grown Under

Protected Condition ........................................................... 186 8.12.1 Prominent Phytonematodes Associated

with Vegetable Crops ....................................... 186 8.12.2 Prominent Phytonematodes Associated

with Flower Crops ............................................ 186 8.12.3 Belowground Feeders ...................................... 187 8.12.4 Aboveground Feeders ...................................... 187 8.13 Landscape Plants ................................................................ 190 8.13.1 Symptoms ........................................................ 190 8.13.2 Management ..................................................... 190 8.13.3 Foliar Nematodes ............................................. 193 8.14 Nursery Crops .................................................................... 194 8.14.1 Important Phytonematodes of Nurseries .......... 194 8.14.2 Sanitation and Preventive Maintenance ........... 195 8.15 Noncommercial Vegetable Garden .................................... 196 8.15.1 Damage and Symptoms by Nematodes ........... 196 8.15.2 Root-Knot Nematodes ..................................... 197 8.15.3 Ectoparasites .................................................... 198 8.16 Home Lawns ...................................................................... 199 8.16.1 Symptoms ........................................................ 199 8.16.2 Management ..................................................... 199 8.17 Bedding Plants ................................................................... 200 8.17.1 Management ..................................................... 200 8.18 Mushrooms ........................................................................ 202 8.18.1 Symptoms ........................................................ 202 8.18.2 Management ..................................................... 202 References ....................................................................................... 202

Contents

xix

9 Nematode Disease Complexes ...................................................... 207 9.1 Interactions in the Soil Ecosystem ..................................... 209 9.2 Mechanisms Involved in Interaction Between

Nematodes and Other Microorganisms.............................. 210 9.2.1 Host Modifi ers ................................................. 210 9.2.2 Vectors of Fungal Pathogens ............................ 211 9.2.3 Mechanical Wounding Agents ......................... 211 9.2.4 Rhizosphere Modifi ers ..................................... 212 9.2.5 Resistance Breakers ......................................... 214 9.3 Lectin-Mediated Nematode–Fungus Interaction ............... 216 9.4 Indirect Effects of Complexes

on Associated Organisms ................................................... 217 9.5 Nematode–Fungal Interactions .......................................... 217 9.6 Nematode–Bacterial Interactions ....................................... 218 9.7 Nematode–Virus Interaction .............................................. 222 9.7.1 The Transmission Process ................................ 225 9.7.2 The Nematode–Virus–Plant Interaction ........... 226 9.7.3 Specifi city of Transmission .............................. 227 9.7.4 Factors Affecting Specifi city, Exclusivity,

and Complementarity in Vector Transmission ..... 228 9.8 Nematode–Rhizobia Interaction ........................................ 229 9.8.1 Nematodes Versus Rhizobial Population

and Infection .................................................... 229 9.9 Nematode–Mycorrhiza Interactions ................................... 231 9.9.1 Benefi cial Effects of AMF ............................... 231 9.9.2 Mechanisms Adopted During Interaction ........ 233 References ....................................................................................... 235

10 Genetics of Nematode Parasitism ................................................ 239 10.1 The Role of Various Secretions in Parasitism .................... 239 10.1.1 Amphidial Secretions ....................................... 240 10.1.2 Esophageal Glands Secretions ......................... 242 10.1.3 Cuticular Secretions ......................................... 242 10.2 Niches Occupied by Phytonematodes ................................ 243 10.3 Convergent Specializations of Feeding Modes .................. 243 10.4 Cellular Changes ................................................................ 246 10.5 Physiological Variation ...................................................... 247 10.5.1 Pathotype .......................................................... 247 10.5.2 Biotype ............................................................. 247 10.5.3 Race .................................................................. 248 10.5.4 Nematode–Host Interaction ............................. 248 10.6 Genetic Models of Plant Parasitism by Nematodes ........... 248 10.7 Parasitism Genes ................................................................ 250 10.8 Genetic Analysis of Nematode Parasitism ......................... 252 10.8.1 Cell Wall-Digesting Enzyme ........................... 254 10.8.2 Expansins ......................................................... 255 10.8.3 Metabolic Enzymes .......................................... 257 10.8.4 Ubiquitination/Proteasome Functions .............. 257 10.8.5 Venom Allergen Proteins ................................. 257 10.8.6 Calreticulin ....................................................... 259 10.8.7 Annexin ............................................................ 260 10.8.8 Avirulence Genes ............................................. 262

Contents

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10.9 Defense Signaling .............................................................. 267 10.10 Molecular Basis for Nematode Resistance ........................ 267 10.10.1 Gene-for-Gene Hypothesis .............................. 268 10.10.2 Steps Involved .................................................. 268 10.11 Identifi cation of Resistance (R) Genes .............................. 268 10.12 Identifi ed R Genes Against Nematodes ............................. 269 10.13 Origin of Parasitism Genes ................................................ 269 10.14 Nuclear Localized Parasitism Proteins .............................. 271 10.14.1 RanBPM ........................................................... 271 10.14.2 Ubiquitination/Proteasome .............................. 272 10.14.3 The 14-3-3 Protein Family ............................... 272 10.14.4 Surface Defense ............................................... 273 10.14.5 Stealth Signals .................................................. 273 10.14.6 Bioactive Peptides ............................................ 274 10.14.7 Chorismate Mutase .......................................... 275 10.15 Genetic Analysis of Parasitism .......................................... 276 10.15.1 Molecular Analysis of Genes ........................... 276 10.16 Nematode Genomics .......................................................... 277 10.17 RNA Interference in Phytonematodes ............................... 278 10.18 Evolution of Parasitism ...................................................... 279 10.19 Horizontal Gene Transfer (HGT) in Nematodes ................ 280 10.20 Identifying “Parasitism Genes” .......................................... 284 10.21 Mechanisms Involved ........................................................ 285 10.21.1 Gene–Gene Relationship ................................. 286 10.21.2 Changes in Gene Expression ........................... 287 References ....................................................................................... 287

11 Nematological Techniques ............................................................ 293 11.1 Sampling for Phytonematodes ........................................... 293 11.1.1 Suitable Time to Collect Soil Samples ............ 294 11.1.2 Where to Look for Sample? ............................. 294 11.1.3 How to Collect Soil Sample? ........................... 295 11.1.4 How to Decide the Number of Soil Cores? ...... 295 11.1.5 Sampling Tools ................................................ 296 11.1.6 Care of Samples After Collection .................... 296 11.1.7 Considerations to Design Sampling

Procedures ........................................................ 296 11.1.8 Field Mapping .................................................. 296 11.1.9 Sampling in Different Crops ............................ 297 11.2 Techniques of Nematode Extraction .................................. 300 11.2.1 Techniques of Nematode

Extraction from Soil ......................................... 300 11.2.2 Techniques to Extract Cyst Nematodes ........... 307 11.2.3 Technique to Enhance Extraction

of Nematodes from Clayey Soils ..................... 308 11.2.4 Techniques of Extraction of Nematodes

from Plant Tissues ............................................ 308 11.2.5 Techniques for the Extraction of Eggs

from Cysts ........................................................ 310

Contents

xxi

11.3 Precautions to Be Taken While Extracting Phytonematodes ................................................................. 311

11.4 Techniques of Handling, Killing, Fixing, Staining, and Mounting of Phytonematodes ..................................... 312

11.4.1 Examination of Nematode Suspensions ........... 312 11.4.2 Transferring Nematodes ................................... 312 11.4.3 Technique of Picking Nematodes .................... 312 11.4.4 Technique of Anesthetizing Nematodes .......... 313 11.4.5 Technique of Sterilization and Inoculation

of Nematodes ................................................... 313 11.4.6 Techniques of Killing and Fixing

Nematodes ........................................................ 313 11.4.7 Technique for Killing and Preserving

Nematodes in Soil Samples Before Extraction ......................................................... 314

11.4.8 Fixatives and Preservatives Used for Nematode Fixing ........................................ 315

11.4.9 Formalin–Glycerin Technique (FG Fixation) for Fixing Nematodes ........................................ 315

11.4.10 Techniques of Staining Nematodes .................. 316 11.4.11 Technique of Mounting Nematodes ................. 317 11.4.12 Mounting Nematodes in Temporary Slides ..... 317 11.4.13 Technique of Mounting Nematodes

in Permanent Slides .......................................... 318 11.4.14 Major Steps for Preparation

of Nematode Mounts ........................................ 319 11.4.15 Mounting Nematodes ....................................... 319 11.4.16 Technique to Prepare Permanent Mounts

of Nematodes Within Plant Tissues Stained with Cotton Blue or Acid Fuchsin ................... 320

11.4.17 Technique of Remounting ................................ 320 11.4.18 Techniques of Preservation and Staining of

Nematodes in Plant Tissues ............................. 321 11.4.19 Technique for Retaining Green Color

of the Plant Material ......................................... 321 11.4.20 Technique to Preserve Juveniles

of Meloidogyne spp. . ....................................... 321 11.4.21 Technique to Preserve Infected Roots .............. 321 11.4.22 Technique for Killing and Preserving

Nematodes in Soil Samples Before Extraction ......................................................... 321

11.4.23 Staining Techniques ......................................... 322 11.5 Histopathological and Histochemical Techniques

(Microtome Techniques/Microtomy) ................................. 325 11.5.1 Types of Sections ............................................. 326 11.5.2 Spectroscopic Sections ..................................... 326 11.5.3 Microtechniques in Phytonematology ............. 326

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11.6 Techniques to Evaluate Botanicals Against Phytonematodes .................................................... 331

11.6.1 Technique to Screen Plants for Their Effi cacy Against Nematodes............. 331

11.6.2 Effect on Nematode Mortality ......................... 331 11.6.3 Effect on Egg Hatching .................................... 331 11.6.4 Techniques to Study the Effects of Few

Physicochemical Factors on the Nematicidal Property of Botanicals ...................................... 332

11.6.5 Preparation of the Plant Leaf Extract ............... 333 11.6.6 Effi cacy of Chopped and Finely Ground

Plant Leaves Mixed in Soil Under Green House Conditions ............................................. 333

11.6.7 Field Evaluation of Nematicidal Plants Against Phytonematodes ....................... 333

11.6.8 Technique to Isolate and Characterize the Active Principles of Nematicidal Plants ...... 333

11.6.9 Identifi cation of Constituents ........................... 334 11.7 Techniques of Remote Sensing .......................................... 334 11.7.1 Remote Sensing Techniques

Used in Plant Protection ................................... 335 11.7.2 Aerial Photography .......................................... 335 11.7.3 Aerial Videography .......................................... 335 11.7.4 Multispectral Sensing (MSS) ........................... 336 11.7.5 Radar ................................................................ 336 11.7.6 Sodar ................................................................ 337 11.8 Technique of Soil Solarization ........................................... 337 11.8.1 Points to Consider ............................................ 337 11.8.2 Plastic Tarp ....................................................... 338 11.8.3 Other Benefi ts .................................................. 339 11.8.4 Factors Infl uencing the Success ....................... 339 11.9 Technique of Soil Fumigation ............................................ 339 11.9.1 Methyl Bromide ............................................... 340 11.9.2 Soil Preparation Schedule ................................ 340 11.9.3 Fumigant Application ...................................... 341 11.9.4 Methyl Bromide Fumigation

of Polyhouse Soils............................................ 341 11.9.5 Safety Precautions ............................................ 342 11.10 Microplot Techniques ........................................................ 343 11.10.1 Types of Microplots ......................................... 344 11.10.2 Preparation and Infestation of Microplots ....... 344 11.10.3 Major Limitations of Microplots ..................... 345 11.11 Techniques of Evaluating Nematicides .............................. 345 11.11.1 Procedure for Measuring the Root- Knot

Infestation by Using the “Indicator Plants” .......... 346 11.11.2 General Methods .............................................. 346 11.11.3 Publicity to the Farmers ................................... 347 11.11.4 Collection of Data ............................................ 348 11.11.5 Types of Specifi c Techniques ........................... 348 11.11.6 Points to Remember ......................................... 350

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11.11.7 Preliminary Screening of Nematicides ............ 350 11.11.8 Techniques to Test the Effi cacy

of Nematicides ................................................. 351 11.12 Crop Loss Assessment Due to Nematodes ........................ 354 11.12.1 Strategies for Loss Assessment ........................ 355 11.12.2 Quantifi cation of Nematode/Disease ............... 356 11.12.3 Collection of Data to Measure

the Disease–Loss Relationship ........................ 356 11.12.4 Mathematical Models for Crop

Damage Assessment ........................................ 358 11.12.5 Types of Models ............................................... 358 11.12.6 Modeling of the Disease–Loss

Relationship ..................................................... 361 11.12.7 Model Validation and Prediction ..................... 362 11.12.8 Parameter Measurement and Estimation.......... 363 11.12.9 Development and Use of Regional

Crop Loss Databases ........................................ 364 11.12.10 Nematode Damage Models .............................. 364 11.12.11 Approaches of Estimating Yield Losses .......... 365 References ....................................................................................... 366

12 Nematodes of Quarantine Importance ........................................ 369 12.1 Biosecurity Implications .................................................... 371 12.2 Nematodes Under Quarantine Act ..................................... 372 12.2.1 Potato Cyst Nematodes .................................... 372 12.2.2 Golden Cyst Nematode of Potato

( Globodera rostochiensis ) ................................ 373 12.2.3 Pale/White Cyst Nematode of Potato

( Globodera pallida ) ......................................... 373 12.2.4 Stem and Bulb Nematode

( Ditylenchus dipsaci ) ....................................... 376 12.2.5 Potato Rot Nematode

( Ditylenchus destructor ) .................................. 378 12.2.6 The Burrowing Nematode ( Radopholus

similis/R. citrophilus ) on Citrus ....................... 379 12.2.7 Procedure for Quarantine Inspection

for Nematodes .................................................. 381 12.2.8 Molecular Aids to Nematode Diagnosis .......... 382 12.2.9 Avoiding Infi ltration

of Nematodes/Restricting the Spread ............... 383 12.2.10 Some Requirements and Solutions .................. 384 12.2.11 Future Thrusts .................................................. 384 References ....................................................................................... 384

13 Novel Methods of Nematode Management ................................. 387 13.1 Plant Nematode Resistance Genes ..................................... 388 13.2 Manipulation of Natural Resistance Genes ........................ 390 13.3 Application of Recombinant DNA Technology ................. 390 13.3.1 Broad Classes of Transgenic

Nematode Control Strategies ........................... 391 13.3.2 Targets for Novel Transgenic Resistance ......... 391

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13.3.3 Targeting Feeding Cells Required by Nematodes ................................................... 392

13.3.4 Targeting the Nematode Directly ..................... 392 13.3.5 Molecules for Transgenic Expression .............. 393 13.3.6 Plantibodies ...................................................... 393 13.3.7 Proteinase Inhibitors ........................................ 394 13.3.8 Promoters ......................................................... 396 13.4 Nematode Ecdysteroids ..................................................... 397 13.5 Inhibition of Sterol Metabolism ......................................... 399 13.6 Phytoecdysteroid ................................................................ 400 13.7 Juvenile Hormone (JH) in Nematode Management ........... 401 13.8 Vertebrate Steroid Hormones ............................................. 402 13.9 DAPG (2,4-Diacetylphloroglucinol) .................................. 402 13.10 Avermectins ....................................................................... 403 13.10.1 Mechanism of Action ....................................... 403 13.11 Lectins ................................................................................ 404 13.12 Endotoxins of Bacillus thuringiensis (Bt).......................... 406 13.13 Bio-fumigation ................................................................... 407 13.13.1 General Procedure of Bio-fumigation .............. 409 References ....................................................................................... 410

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Dr. N. G. Ravichandra obtained his Ph.D. degree in plant pathology with plant nematology as specialization, in 1988 from the University of Agricultural Sciences, Gandhi Krishi Vignan Kendra Campus, Bangalore, Karnataka, India. He is presently working as Professor & Scheme Head, AICRP (Nematodes), Department of Plant Pathology, a nematologist and head, All India Coordinated Research Project on Plant Parasitic Nematodes, Department of Plant Pathology, University of Agricultural Sciences, GKVK Campus, Bangalore, Karnataka, India, and is involved in teaching, research, and extension activities in plant nematology. He has been a major advisor to the postgraduate students majoring in plant nematology for M.Sc. (Agri.) and Ph.D. degree programs.

Dr. N. G. Ravichandra has over 152 scientifi c publications to his credit in national and international journals. He has authored three textbooks entitled Plant Nematology , Methods and Techniques in Plant Nematology , and Fundamentals of Plant Pathology published by the reputed publishers and contributed chapters to several textbooks and authored ten books in Kannada on various aspects of plant protection including nematology. He has also edited books and chapters related to plant nematology.

He has participated and presented original papers on various aspects related to phytonematodes in several national and international conferences. He has undergone advanced training programs on nematodes sponsored by the Department of Biotechnology and Indian Council of Agricultural Research, New Delhi, India. He has operated research projects pertaining to phytonematodes funded by the Department of Biotechnology and Indian Council of Agricultural Research, New Delhi, India, as principal investigator and coprincipal investigator.

He was involved in developing six technologies for the management of root-knot nematodes infecting tomato, brinjal, and rice which have been included in the Package of Practices of University of Agricultural Sciences, Bangalore, Karnataka, India, for the use by the farmers. He is an active life member for several professional societies including Nematological Society of India, Indian Phytopathological Society, Society of Mycology and Plant Pathology, National Environmental Science Academy, and Institute of Agricultural Technology.

About the Author