Characteristics of Nematodes

AGR154

Chapter Overview

Characteristics of nematode

Reproduction of nematodes

How nematodes affect plant

Isolation of nematodes from soil

Introduction

Kingdom = Animalia

Phylum = Nematoda

Important genus:

Heterodera = cyst nematodeMeloidogyne = root-knot nematodeLive in fresh or salt water or in the soil

Morphology of Plant Pathogenic Nematodes

Small , 300 to 1000 micrometers long

15-35 micrometers wide (invisible to naked eyes)

Eel shape and round in cross section

Smooth, unsegmented bodiesWithout legs or other appendages

Anatomy

More or less transparent (covered by a colorless cuticle)

The cuticle is produced by the hypodermis

The cuticle will extend to the body cavities as four chords

The four chords will separating into four bands of muscles

The muscles enable the nematode to moveBody cavity contains a fluid – circulation and respiration take place)

Anatomy

Hollow tube digestive systems- starting from mouth- esophagus- intestine – rectum and anus.

6 lips surround the mouth

Have a hollow stylet or spear (use to puncture holes in plant cells and take the nutrients from cell)

Reproduce through eggsMay be sexual or parthenogenetic (development of embryos occurs without fertilization by a male)

1. Female reproductive system One or two ovariesFollowed by oviduct and uterus terminating in a vulva

2. Male reproductive systemHas testis and seminal vesicleHas a pair of protrusible and copulary spicules

Reproduction

Cross Section of Female Nematodes

Nematodes Lips

Life Cycle

4 steps/phases

Eggs

4 juvenile stages

Adult

Egg produced

Eggs hatch into juvenileJuveniles will enlargeThere are 4 stages of juvenileEach stages will be ended with molting processThe first molt occurs in the eggsAfter the final moult, the nematodes will differentiate into males or females.The female can then produce fertile eggs

Life Cycle

The life cycle may be completed within 2-4 weeks under optimum environmental

Usually the first and second juvenile still could not infect the plantOnce infective stages are produced, they must feed the host

Without host, they might die due to starvation.

HabitatMostly all of plant pathogenic nematodes spend their life in the soil

1. Feeding habitEctoparasite : do not enter into the host tissue

feed only on the host surfaces

Endoparasite : enter and feed the host tissue

2. Feeding sites• Migratory : Moves through plant tissue• Sedentary : establish specialised feeding sites

& stay there until they die.

Location of Feeding

Location of feeding

Feeding habit Example

Endoparasite Migratory Root knot, cyst, citrus

Sedentary Lesion, stem, bulb

Ectoparasite Migratory Ring

Sedentary Stubby root

How Nematodes Affect Plant

Because of feeding process

Puncture a cell wall

Inject saliva- contain enzymesTake the cell contentsAnd moves on within a few seconds

Isolation of Nematodes From Soil

Baermann Funnel method:

Extract live nematodes from soil

Nematodes move out from the soil into the water,

Then, they will fall to the bottom of the funnel

Baermann Funnel Set Up

Soil sample over wire mesh

Funnel

Beaker

Clamp

Rubber tubing

Clamp to hold funnel

Put a wire mesh into the funnel. Add a water into the funnelA piece of rubber tube is attached to the funnel . A clamp is used to hold the funnelPut a beaker below the rubber tubeAdd soil sample into the porous paperPlace the sample onto the funnel. Cover the tissue over the soilIncubate for 48 hours and collect the nematodesThe nematodes moves actively from the porous paper into the water and sink at the bottom of rubber tubing.