Plant Disease Caused by Nematode

by Asst. Prof. Pornsuk Chaisuk

Kingdom : AnimaliaPlylum : Nematoda

- free living- plant/animal parasite

Types of nematode>100,000,000 species but only 20,000 species were named

Animal nematode 15%

Plant nematode 10%

Marine nematode 50%

Free-living nematode 25%

Animal and human nematodes

- Ascaris lumbricoides พยาธิในลาํไส/้พยาธิไสเ้ดือน- Trichinella spiralis พยาธิเนื�อหมู - Gnathostoma spiningenum พยาธิตวัจิ�ด- Ancylostoma duodenale พยาธิปากขอ (hookworm)- Wuchereria bancrofti สาเหตุโรคเทา้ชา้ง

Important plant nematodes

- Globodera rostochinensis : potato -> stunt

- Ditylenchus dipsaci : oat, rye, rice, onion, sugar beet

and other bulb plants -> bloat/

swollen

- Meloidogyne spp. : tomato, chilli, potato, caroot, okra,

soybean, grass and other plants ->

gall

History of nematode discovery

A.D.1656 : Nematode was first discovered after the invention of a microscope by P. borellus. First nematode was Turbatrix aceti (vinegar eel) that free living nematode lived in vinegar.A.D. 1743 : First plant nematode was discovered J.T. Needham. It was Anguina trtiici that lived in the swollen wheat seed.

History of important plant nematodes

Nematode Plant Discoverer Year

Anguina tritici wheat J.T. Needham 1743

Meloidogyne spp. cucumber M.J. Berkeley 1855

Ditylenchus dipsaci fuller’s teasel Julius Kuhn 1857

Heterodera schachtii sugar beet H. Schacht 1859

Globodera rostochiensis potato Julius Kuhn 1881

Father of nematology

Nathanial A. Cobb (1859-1932) is an important person for the study of nematodes in terms of discovering various types of nematodes. The invention of methods for the study of nematodes And being the creator of various words for use in nematology

Morphology of Plant Nematode

- Small size cannot be seen with the naked eye (approximately 250-1,200 micrometres in length, 15 micrometres in width) except in the cyst stage- The appearance is filiform liked eel shaped worms, except some genus in adult females stage- The body is unsegment and without appendages- Bilateral symmetry- Female cyst and some adult female have many shapes

Male

Female

Sedendtary endoparasites : Appearance1. Globodera sp. : body spherical,

forming cyst2. Heterodera sp. : body lemon-

shaped, forming cyst3. Meloidogyne sp. : body pear-

shape, no cyst4. Rotylenchulus sp. : body kidney-

shaped, no cyst

1

4

3

2

Sedentary endoparasites : Appearance

1. Cyst form (Globodera sp., Heterodera sp.) : dead female But there is still eggs inside2. Root knot nematode (Meloidgyne sp.) : lays eggs on the buttom outside the body, eggs are covered with gelatin “egg mass”

ovary

ovary

spicule

annules Lateral linestylet

anus

vulva

median bulb

excretory pore

esophagusintestine

Morphology of plant nematodes

Feeding of nematode

- free living : intracorporeal digestion

- plant parasite : extracorporeal digestion

Free living

Plant parasite

Nematode life cycle

1st molting

1st juvenile

egg

fertilization adult 4th molting

3rd molting

2nd molting

4th juvenile

3rd juvenile

Inside egg outside egg

2nd juvenile

Taxonomy of nematodes by Chitwood (1950)

Kingdom AnimaliaPlylum Nematoda : 2 class

1. Class Secernentea : phasmid present (phasmid is sensory organs at posterior)

2. Class Adenophorea : phasmid absent

Plant nematode- 95% in Class Secernentea

Order Tylenchida- 5% in Class Adenophorea

Order Dorylaimida

Classification of nematodes based on behavior

- classification of nematodes by host- classification of nematodes by feeding habits- classification of nematodes by movement

Classification of nematodes by host

1. Phytophages : plant2. Microbivore : bacteria3. Fungivore : fungi4. Omnivore : vertebrates, invertebrates5. Predators : other nematode6. Animal parasite : vertebrates, invertebrates7. Saprophyte

Classification of nematodes by feeding habits

1. Ectoparasitic nematode 2. Endoparasitic nematode3. Semi-endoparasitic nematode

Classification of nematodes by movement

1. Migratory parasitic nematode2. Sedentary parasitic nematode

Ectoparasitic nematode

Hoplolaimus

Criconemella

Helicotylenchus

Ditylenchus

Helicotylenchus spp. (Spiral nematode)

Hoplolaimus spp. (Lance nematode)

Criconemella spp. (Ring nematode)

Maize

Xiphinema spp. (Dagger nematode)

Endoparasitic nematode

Meloidogyne

Heterodera

Rotylenchulus

Male

Female

Meloidogyne spp. (Root knot nematode)

Female

Egg mass

Meloidogyne spp. (Root knot nematode)

Rotylenchulus reniformis (Reniform nematode)

Maize

Heterodera zeae (Cyst Nematode)

Soybean

Heterodera glycines (Cyst Nematode)

cyst

Potatocyst

Globodera rostochiensis (Gloden nematode)

Classification of nematodes by feeding habits movement and position

- Below ground migratory ectoparasites : Helicotylenchus spp., Hoplolaimus spp., Criconemella spp.,

Xiphinema spp., Longidorus spp., Trichodorus spp., Paratylenchus spp.- Below ground migratory endoparasites :

Pratylenchus spp., Radopholus spp.- Below ground sedmentary semi-endoparasites and endoparasites :

Rotylenchulus spp., Tylenchulus spp., Heterodera spp., Globodera spp., Meloidogyne sp., Nacobbus spp.

- Above ground endoparasites : Anguina spp., Ditylenchus spp., Aphelenchoides sp.

Pratylenchus penetrans

Trichodorus christiciHemicycliophora arenaria

Heterodera spp.Meloidogyne spp.

Nematode parasitism

1. Direct- wound- lack water and mineral- change plant physiology

2. Indirect- open the way for other microorganisms- nematode vectors of plant viruses

Mechanical for plant cell damage

1. Removal of cell contents2. Cell lysis3. Iduction of specialized feeding cells4. Systemic effects

Mechanisms for host disturbance by nematodes

1.1. No visible destructive effect

Migratory ectoparasites (short stylet): Root hair- Tylenchorhynchus spp.- Paratylenchus spp.

1.2. Immediate removal of cell contents

Migratory ectoparasites: Epidermis- Aphelenchoides spp.

1.3. Delayed removal of cell contents

Migratory and sedentary ectoparasites.: Cortex & Endodermis- Helicotylenchus spp.- Trichodorus spp.- Paratrichodorus spp.-Hemicycliophora spp.- Belonolaimus spp.- Ditylenchus myceliophagus

2.1. Progressive penetration

Migratory endoparasites: Cortex- Pratylenchus spp.- Radopholus spp.

2.2. Cell lysis

: Root tip & Meristem- Ditylenchus spp.

3.1. Nurse cells of Tylenchulus

3.2. Syncytium of Nacobbus

3.3. Syncytium of Heterodera

3.4. Giant cells of Meloidogyne

Sedentary parasites : feeding cells

Nurse cell Syncytium Giant cell

Interaction of nematodes with other microorganisms

1. Be vector of the other microorganisms.2. Make physical wound that the way for the other microorganisms.3. Make the leakage of attractants or nutrients that attract other plant pathogens to infect the plant.4. When plant cells die, the other microorganisms attack them repeatedly.5. Change plant physiology/biochemistry then plant is weak.

synergism = เสริมกนัantagonism = หักล้างกนั

Interaction of nematodes with virus

Virus can be transmitted by nematodes must# be seed borne and pollen borne# transmit by mechanical method

Types of nematode transmitted viruss

1. NEPO Viruses = Nematode Transmitted Polyhedral Shaped Viruses => # arabis mosaic virus

# strawberry latent ring spot virus transmitted by juvenile+adult of Xiphinema sp. &

Longidorus sp.2. NETU Viruses = Nematode Transmitted Tubular Shaped

Virus => # tobacco rattle virus# pea early browning virustransmitted by juvenile+adult of Trichodorus sp.

Nematode vectors of plant viruses

- Viral transmission occurs after the release of enzymes while the nematodes feed nutrients from plants.- virus don’t transmit to the nematode eggs.- No increase the amount of virus in the nematode.- After the molting, the virus will come out of the cuticle or in the small intestine.

Plant nematode diseases

1. Root galls or Root knots : Meloidogyne sp. induces root cells to begiant cells by hypertrophy and hyperplasia.

2. Root lesion : Pratylenchus sp. penetrates and migrates inside root tissue.

3. Stubby roots : Trichodorus sp. penetrates meristematic tissue of corn root then root is necrosis and stubby

4. Spring dwarf or Crimp : Aphelenchoides fragariae makes strawberry has many shoots; make lychee stunts; begonia leaf is brown and necrosis.5. White tip : Aphelenchoides besseyiinfects rice leaf tip.

6. Seed gall : ของขา้วสาลีและขา้วไรย์ เกิดจากไสเ้ดือนฝอย Anguina tritici infect wheat and rye seeds and live in infected seed for many year. One seed can have 800-32,400 nematodes.

7. Chrysanthemum leaf blight : Aphelenchoides ritzema-bosi is endoparasitic nematode, infect plant through guard cell.

Important plant nematode

Disease cycle of root-knot nematode Meloidogyne sp.

Life cycle 25 days

Disease cycle of the lesion nematode Pratylenchus sp.

Nematodes in root cortex

Lesions on peanut pods, Florida.

Disease cycle of the stem and bulb nematode Ditylenchus dipsaci

Life cycle 19-25 days

Ditylenchus dipsaci (Stem and bulb nematode)

Ditylenchus angustus

Rice Stem nematode

Disease cycle of the foliar (chrysanthemum) nematode Aphelenchoides ritzema-bosi

Life cycle 2weeks

Disease cycle of the stubby-root nematode Trichodorus christii

Life cycle 20 days

Nematode damage to corn roots

Plant nematode control

1. Cultural control- release flooding- soil solarization - leave the fields fallow- sanitation- crop rotation- applying manure, compost or green manure- using sterile seeds and seedlings- using resistant or tolerant varieties and rootstocks

2. Biological control- using nematode-toxic plants- using natural predators or pathogens of nematodes • antagonistic fungi : Purpureocillium lilacinum

(Paecilomyces lilacinus)• antagonistic bacteria : Pasteuria penetrans

3. Chemical control

Fumigants Non-fumigants

Methyl bromide Furadan

Dazomet Vydate

Mocap

Rubby

Nemacur