Phytonematodes

1. Introduction to
Phytonematodes: Biology,
Ecology, and Management
Dr Showkat Ahmad
Wani

2. Introduction
• Definition: Phytonematodes are microscopic, non-
segmented roundworms that parasitize plants.
• Importance: Cause significant crop losses globally—
estimated to be over $80 billion annually.
• Host range: Affect a wide range of crops including cereals,
vegetables, fruits, and ornamentals.

3. Classification
and Types
Phylum: Nematoda
• Tylenchida (most important plant
parasites)
• Dorylaimida
Major Orders of
Phytonematodes:
• Meloidogyne (Root-knot nematodes)
• Heterodera, Globodera (Cyst nematodes)
• Pratylenchus (Lesion nematodes)
• Radopholus, Rotylenchulus, Nacobbus
Common Genera:

4. Meloidogyne
Heterodera

5. Pratylenchus
Rhadopholus
Rotylenchulus
Nacobbus

6. Morphology and Biology
Body shape: Cylindrical, elongated, unsegmented
Size: 0.3 to 3 mm in length
Feeding structures:
• Stylet: Needle-like structure for piercing plant cells
Life cycle:
• Egg Four juvenile stages (J1–J4) Adult
→ →
• Life cycle duration: 3–4 weeks under ideal conditions

7. Life Cycle

8. Symptoms of Infestation
• Above-ground symptoms:
• Stunting, yellowing, wilting
• Poor yield and growth
• Below-ground symptoms:
• Root galls (e.g., Meloidogyne)
• Root lesions (Pratylenchus)
• Stubby roots, excessive root branching

9. Host-Parasite Interactions
• Ectoparasites: Feed from outside the root (e.g., Xiphinema)
• Endoparasites:
• Migratory (e.g., Pratylenchus)
• Sedentary (e.g., Meloidogyne, Heterodera)
• Mechanism of damage:
• Disruption of water/nutrient uptake
• Formation of giant or syncytial cells
• Facilitation of secondary infections (e.g., fungi, bacteria)

10. Management Strategies
A. Cultural Methods
• Crop rotation
• Deep ploughing
• Fallowing and soil solarization
B. Biological Control
• Pasteuria penetrans (bacterial parasite)
• Fungi like Paecilomyces lilacinus, Trichoderma spp.
C. Chemical Control
• Nematicides: Carbofuran, Fenamiphos
• Limitations: Environmental risk, cost
D. Resistant Varieties
• Use of nematode-resistant cultivars (e.g., tomato varieties resistant to
Meloidogyne)
E. Integrated Nematode Management (INM)
• Combining cultural, biological, and chemical methods

11. Emerging Approaches
• Molecular diagnostics: PCR-based detection of nematodes
• RNA interference (RNAi) for gene silencing in nematodes
• Biotechnological tools: Transgenic crops expressing anti-
nematode genes

12. Conclusion
• Phytonematodes are serious hidden enemies of crops.
• A multidisciplinary approach is essential for sustainable
management.
• Awareness and training of farmers and extension workers
can significantly reduce losses.

13. • Thank You