Practical 9: Nematode: Morphology, Life cycle and Disease Symptoms

INTRODUCTION
Nematode is belongs to the kingdom Animalia. Nematode have similar appearances with worm but distinguish taxonomically from the worms. Some species of nematode feed on living plants causing variety of plant diseases worldwide which causes economic losses every year. All plant parasitic genera belong to the order of Tylenchida but some belongs to the order of Dorylaimida. The morphology of plant parasitic nematodes can be differentiated in shape and size but generally they are eel shaped, unsegmented bodies and without legs or other appendages. They are too small for naked eye but easily observed under microscope. All nematode have four juvenile stages. At the first molt, nematodes differentiate into males and females. The female can produce fertile eggs either after mating with a male or in the absence of males,parthenogenetically. Nematode infections of plant results in appearance of abnormal shape of root or symptoms on root as well on the aboveground. Root symptoms include root lesion, root knots or root galls, excessive root branching and injured root tips. The damage to the roots resulting in the appearance of reduced growth, symptoms of nutrient deficiencies such as yellowing of foliage, excessive wilting on hot dry weather, reduced yields and poor quality of products.
OBJECTIVES
  1. To observe the morphology of nematode under slide preparations.
  2. To differentiate between male and female nematodes.

METHOD
  1. Observe the following slide preparations:
  1. General shape of nematode (worm shape)
  1. Spherical-shaped adult nematode
  1. Kidney-shaped adult nematode
  1. i) Parasitic nematode

      4. ii) Non-parasitic nematode
  1. i) Stomatostylet
    5. ii) Odontostylet
  1. i) Dorylaimid




    6. ii)Tylenchid
  1. i) Female nematodes
  1. i) Sphere-shaped
    8. ii) Semi-sphere shaped




    8. iii) Cone shaped
B) Observe the following slide preparations:
  1. Adult female Meloidogyne with eggs in the root.

  1. Stage 3 Meloidogyne larvae in the root.

  1. Adult male Meloidogyne


  1. Adult female Rotylenchulus with eggs outside of the root
  1. Adult female Rotylenchulus in the root
  1. Adult male Rotylenchulus 





C) Observe the demonstration of symptoms of diseases caused by nematode
  1. Okra root that has been attacked by Meloidogyne sp.

  1. Rice root that has been attacked by Hirschmaniella oryzae











  1. Chili root that has been attacked by Meloidogyne sp. 

  1. Tomato root has been attacked by Meloidogyne sp.

  1. Cucumber root that has been attacked by Meloidogyne sp. 

  1. Guava root that has been attacked by Meloidogyne sp.
D) A diagrammatic example of a life cycle of plant parasitic nematode.

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