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Lesion Nematodes

Lesion Nematodes. Etymology. Pratylenchus First described species was named Tylenchus pratensis Tyenchus pra tensis = Pratylenchus Lesion nematode Characteristic symptom produced on roots Meadow nematode First species recorded in meadows (grasslands). Historical.

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Lesion Nematodes

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  1. Lesion Nematodes Walia CCSHAU

  2. Etymology • Pratylenchus • First described species was named Tylenchus pratensis • Tyenchuspratensis = Pratylenchus • Lesion nematode • Characteristic symptom produced on roots • Meadow nematode • First species recorded in meadows (grasslands) Walia CCSHAU

  3. Historical • De Man (1880) described the first species, Tylenchuspratensisfrom Netherlands on meadows • Filipjev (1936) erected the genus Pratylenchus • Associated with Peach Replant Problem in Canada. First proof of nematode pathogenicity as per Koch’s postulates • Mayne & Subramanian (1933) reported first lesion nematode, Pratylenchuscoffeaeon coffee in Karnataka Walia CCSHAU

  4. Systematic Position Walia CCSHAU

  5. Diagnostic Characters • Female • Length 0.3 – 0.9 mm, vermiform; body gradually tapering posteriorly; head continuous with body, truncate with strong cephalic sclerotization. Stylet strong, 15-20 µm, with well-developed knobs; oesophageal glands overlap ventral. Female genital tract monodelphic, prodelphic, vulva posterior. Tail conoid/cylindrical. • Male • Bursa extending up to tail tip. Walia CCSHAU

  6. Diagnosis Walia CCSHAU

  7. Adult Female Walia CCSHAU

  8. Economically Important Species, Hosts and Distribution Walia CCSHAU

  9. Biology & Life Cycle • Migratory endoparasites • All stages infective • Zone of active growth preferred penetration site • Movement intra- and intercellular in cortex only • Eggs laid scattered in cortex • Entire life cycle stages in cortex • At sowing soil population is more, root population increases till crop reaches reproductive phase, population tends to move out into soil at crop maturity • After infection in feeder roots, nematodes spread to main roots also • In tropical areas, life cycle is completed in 4-5 weeks Walia CCSHAU

  10. Infection Walia CCSHAU

  11. Intercellular migration Walia CCSHAU

  12. Damage to cortical cells Walia CCSHAU

  13. Intracellular migration Walia CCSHAU

  14. Intracellular Walia CCSHAU

  15. Intracellular Walia CCSHAU

  16. Stained nematodes in cortex Walia CCSHAU

  17. Egg laying in cortex Walia CCSHAU

  18. Symptoms • Above-ground • Stunting, yellowing of leaves, defoliation, poor fruiting, dieback • Below-ground • Discrete elliptical lesions which coalesce as infection spreads, extensive necrosis leads to girdling • Overall root system reduced, necrotic roots colonised by secondary pathogens • Infection spreads to pods, tubers etc also Walia CCSHAU

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  23. Root symptoms - Comparative Walia CCSHAU

  24. Histopathology • Infection confined to cortical parenchyma cells • Extensive cavity formation in cortex due to feeding and migration • No special feeding areas like RKN, cyst nematodes Walia CCSHAU

  25. Mechanism of lesion formation • Peach Replant Problem in Canada studied by Mountain & Patrick during 1950’s • Nematode (P. penetrans) pathogenicity on peach proved according to Koch’s postulates • Koch’s postulates • Constant association of suspect organism with diseased condition • Isolation of suspect organism in pure culture • Inoculation and production of symptoms under aseptic conditions • Re-isolation of same organism from inoculated plants Walia CCSHAU

  26. Mechanism of lesion formation Amygdalin β Glucosidase Sugar + Hydrogen cyanide + Benzaldehyde (Toxic) (Toxic) Walia CCSHAU

  27. Interaction with other pathogens • Nematodes provide not only provide infection courts to fungus but also bring physiological changes in plants which favour fungus colonisation • First proved on P. penetrans+ Verticillium wilt on peppermint Walia CCSHAU

  28. Damage potential Walia CCSHAU

  29. P. coffeaeon Coffee in Karnataka • Losses • Rs 20 million per year in 4000 ha only (1971) • Control • In nursery • Should be raised in nematode-free soil, away from established coffee estates • Site should be free from weeds • Avoid using soil from old coffee plantations • Estate • Dig out sick plants and burn them • New and old plantation sites should be ploughed and soil exposed to drying for at least one season • Apply phenamiphos to young plants @ 3 g per plant every 3 months for at least one year • Grafting of arabica (susceptible) on robusta (resistant) root-stock Walia CCSHAU

  30. Grafting techniqueRoot-stockRobusta CoffeacanephoraScionCoffeaarabica Walia CCSHAU

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