Lab Tuesday: Lab Tuesday: NematodesNematodes

• Quiz for Electron Microscopy (pp.21) and Nematode Extraction from Soils (p. 84 week #1). And intro sections of Nematodes (pp. 83-90).

• Nematodes lab – learn to key out the little critters!

• Observe tomato plants and record data from ‘Biocontrol of Crown Gall’ experiment. One last look at virus inoculations.

• REMINDER: Lab Final is Thursday. The test takes 1 hour; the test is available between 9 and 5 pm.

NEMATODES LIVE IN DIVERSE HABITATSNEMATODES LIVE IN DIVERSE HABITATS- Over 15,000 species described- 200,000 - 500,000 species estimated- Exist in nearly every habitat- From mountain tops to ocean depths- From hot deserts to cold Antarctic soils- 50% marine- 25% “free-living” in soil and freshwater- 15% animal parasites- 10% plant parasites

NEMATODES HAVE DIVERSE DIETSNEMATODES HAVE DIVERSE DIETS

- Algae, bacteria, fungi, yeasts, diatoms- Predators of protozoa and nematodes- Parasites of invertebrates- Parasites of vertebrates (including man)

- Parasites of all parts of plants

IMPORTANT ROLES OF NEMATODES- Model organisms for biological concepts

Genetics, medicine, aging- Diseases of man & domestic animals = worming- Soil health, decomposition and nutrient cycling- Insect parasites for biocontrol of insects- Plant Pathogens

$100 billion annual loss worldwide$ 6 Billion annual yield loss U.S.$10+ million control costs in OregonCan be major obstacles to trade

NEMATODE STRUCTURENEMATODE STRUCTURE

- Invertebrate animals- Unsegmented roundworms “tube within a tube”- Bilaterally symmetrical- Well developed digestive, reproductive,

nervous systems- No circulatory or respiratory system- Longitudinal muscles, but no circular muscles- Lengths range from 0.003 in. to 27 feet!

- Plant-pathogenic nematodes are 0.01-0.22 in.

NEMATODE MORPHOLOGYNEMATODE MORPHOLOGY

- Important to learn basics- Used to identify nematodes- Identification necessary for diagnosing disease

- Touch on most important points- Bring notes to lab tomorrow- Lots of new terms, Don’t panic

Cuticle = outside cover, flexible, semipermeable

Transverse markings = “striae”

Areas between striae = “annules”

Raised area along side of nematode = “lateral field”

No No AnnulationAnnulation Coarse Coarse AnnulationAnnulation

Lateral field with 3 lateral lines

Spicules

MouthMouth

Lips (6 total)Lips (6 total)

Papillae (touch, taste)Papillae (touch, taste)

AmphidAmphid(taste)(taste)

StyletMedianBulb

Intestine

Testis

Egg

Tail

Anus

Postuterine Sac(Present in species with 1 ovary)

Vulva

Intestine

Ovary

Lobe of esophagus glandoverlapping intestine

Spicules in cloaca

Bursa

LipsProcorpus

LateralLines

NEMATODE REPRODUCTION

Amphimixis = males fertilize females

Parthenogenesis = “Females beget females”males unnecessarymales rare or do not exist

A SIMPLIFIED KEY TO SELECTED GENERAOF SOIL-DWELLING PLANT-PARASITIC

NEMATODES

1a. Stylet present (plant-parasitic nematodes) ….…..2(algal and fungal-feeders, predators, etc.)

1b. Stylet absent (Non-parasitic nematodes)(feed on bacteria, algae, yeasts, predators)

2a. Esophagus with median bulb;stylet with basal knobs …………………...………3

2b. Esophagus without median bulb; stylet without basal knobs ………...….…...........13

StyletStylet Without KnobsWithout Knobs StyletStylet With KnobsWith Knobs

Median Bulb

Rhabditida Tylenchida Dorylaimida

Stoma

Procorpus

Isthmus

BasalRegion

Intestine

BarbShaft

Basal knobsStomatostylet

ProcorpusMedian bulb(Metacorpus)

Isthmus

BasalRegion

Intestine

Stylet

StyletExtension

Odontostylet

Replacement Stylet

Procorpus

BasalRegion

NoStylet

Bacterial feeder

Plant pathogen

Plant pathogen and virus vector

ESOPHAGEAL TYPES OF COMMON SOIL NEMATODESESOPHAGEAL TYPES OF COMMON SOIL NEMATODES

LIFE STRATEGIES OF NEMATODES ROOT PATHOGENS

Ectoparasites = body remains outside of plant tissueEndoparasites = whole nematode enters plant tissue

Migratory = move around throughout lifeSedentary = feed in one location only

All combinations of life style exist

LIFE STRATEGIES OF NEMATODES ROOT PATHOGENS

Migratory Ectoparasites - feed outside of root, movecell-to-cell but do not enter root. e.g., dagger nematode

StyletHead

LIFE STRATEGIES OF NEMATODES ROOT PATHOGENS

Sedentary Ectoparasites - head enters root but body remains outside, no movement after this. e.g., citrus nematode

LIFE STRATEGIES OF NEMATODES ROOT PATHOGENS

Migratory Endoparasites - tunnel inside root butmove back to soil and new roots at will.e.g., root-lesion nematode

LIFE STRATEGIES OF NEMATODES ROOT PATHOGENS

Sedentary Endoparasites - tunnel into root and establish feeding site, females do not move but may rupture root as they enlarge e.g., root-knot & cyst nematodes

Root-knot - gall forms around nematode, eggs laid outside

Cyst - no gall, nematode pops out of root, eggs retained in body

LIFE STRATEGIES OF ABOVEGROUND NEMATODES

Nematodes crawl up plant in film of water and/ormigrate inside plant to reach destination

Feeding strategies vary at different points of their life cycles:Migratory ecto→ migratory endo→ sedentary endo

Examples:stem and bulb nematode foliar nematode seed gall nematode

ROOT-LESION NEMATODEPRATYLENCHUSPRATYLENCHUS SPP.SPP.

ROOTROOT--KNOT NEMATODE KNOT NEMATODE MELOIDOGYNEMELOIDOGYNE SPP.SPP.

J1 → J2 in eggJ2 migrate in soil and invade root

J2 find feeding site in root

J2 J2 →→ J3 J3 →→ J4 J4

Feeding causes giant cells

Root forms gall around female Female ruptures root, lays eggs

Growth and moltingGrowth and molting

WORLD’S MOST IMPORTANTPLANT-PATHOGENIC NEMATODES

WeightedImportance

Common Name Genus Life Cycle Strategy RankingRoot-knot Meloidogyne Sedentary Endoparasite 1375Root-lesion Pratylenchus Migratory Endoparasite 782Cyst Heterodera Sedentary Endoparasite 606Stem & Bulb Ditylenchus Diverse Strategies 251Golden Cyst Globodera Sedentary Endoparasite 244Citrus Tylenchulus Sedentary Ectoparasite 233Dagger Xiphinema Migratory Ectoparasite 205Burrowing Radopholus Migratory Endoparasite 170Reniform Rotylenchulus Sedentary Ectoparasite 142Spiral Helicotylenchus Migratory Ectoparasite 122

Nematode Signs and Symptoms

Root-lesion NematodeMigratory endoparasite

Root-knot & Cyst NematodesSedentary endoparasite

NematodesNematodesentering entering rootsroots

= Sign= Sign

LesionsLesions

= Symptom= Symptom

Cysts from soil Cysts from soil = Sign= Sign

Galls on roots Galls on roots = Symptom= Symptom

Questions?

Nematode Management StrategiesFumigant nematicides (Telone, metam sodium)Non-fumigant nematicides (Vydate, Mocap, TemikCrop rotation to poor or non-host cropsPlant resistanceGreen manure cover cropsHeat treatment of propagating material (roots, bulbs)Timing of planting and harvestSolarizationFallowFlooding

SYMPTOMS OFNEMATODE DISEASES

Root Lesion Nematode

Eggs

Symptoms of Root lesionNematode onStrawberry

Symptoms of Root LesionSymptoms of Root LesionNematode in PeppermintNematode in Peppermint

Symptoms of Root LesionSymptoms of Root LesionNematode on ParsnipNematode on Parsnip

Female root knonematode with egg mass

Symptoms of Root Knot NematodeOn Mint

Healthy

Symptoms of Root Knot Nematode

Symptoms of Root Knot Nematode on tomato

Symptoms of Root Knot Nematode

External Symptoms ofColumbia Root Knot Nematode

Internal Symptoms of Root Knot Nematode

Nematode transmitted virus disease:Corky Ringspot of potato

Nematode damage in mint caused by the needle nematode, Longidoriusspp., a migratory ectoparsite

Symptoms of Foliar Nematode on PhloxAphelenchoides spp.