Nematodes David Bird 515-6813 david_bird@ncsu.edu

1. NematodesDavid Bird515-6813david_bird@ncsu.edu • Lecture 1: Nematodes as plant parasites • 4 case studies • Lecture 2: Model systems and the phylum Nematoda • Lecture 3: Nematode anatomy • Lecture 4: Reproduction and development • Lecture 5: Nervous system and behavior • Lecture 6: Adaptations for plant-parasitism 1 • morphology and behavior • Lecture 7: Adaptations for plant-parasitism 2 • genes, genomes and evolution of plant-parasitism • Lecture 8: The world of plant-parasitic nematodes and their control • Exam: November 5 Nematology

2. What are nematodes? • Nematodes are worms Nematology

3. What are nematodes? • Nematodes are worms • Entire animal phylum: Nematoda • (lecture 2) Nematology

4. What are nematodes? • Nematodes are worms • Entire phylum: Nematoda • Formal definition: • Pseudocoelomic • Aquatic • Un-segmented • Molting • Round-worms Nematology

5. What are nematodes? • Pseudocoelomic, aquatic, un-segmented, molting, round-worms • round in transverse section • posterior cross section through adult: • (h) hypodermis: secretes the cuticle • (m) 4 longitudonal muscle blocks • (nc) nerve cord. • (g) gonad • (i) intestine • cylinder within a cylinder Nematology

6. What are nematodes? • Pseudocoelomic, aquatic, un-segmented, molting, round-worms • round in transverse section • posterior cross section through adult. (g) gonad; (h) hypodermal ridge; (i) intestine; (m) muscle; (nc) nerve cord. • Pseudocoelome • Fluid-filled body cavity • “pseudo” not full lined with cells of mesodermal origin Nematology

7. What are nematodes? • Pseudocoelomic, aquatic, un-segmented, molting, round-worms • round in transverse section • posterior cross section through adult. (g) gonad; (h) hypodermal ridge; (i) intestine; (m) muscle; (nc) nerve cord. • pseudocoelome = body cavity not full lined with cells of mesodermal origin • molting • all nematodes have: • egg (embryonic development) • 4 larval (juvenile) stages: L1-L4 (J1-J4) • adult (males, females, hermaphrodites) Nematology

8. What are nematodes? • Elastic cuticle + pseudocoelomic fluid (hydroskeleton) + longitudinal muscles > sinusoidal swimming motion Nematology

9. Nematodes as plant-pathogens • A major problem on many (all?) crops: • banana: 19.7% • citrus: 14.2% • coffee: 15% • corn: 10.2% • soybean: 10.6% • sugar beet: 10.9% • legume forages: 8.2% • Many species ubiquitous & cosmopolitan • some have broad host-range; some are generalists • Chemical control is ineffective and dangerous • many “nematicides” do not kill nematodes Nematology

10. Crop damage: A market analysis Nematode Damage in Billions of Dollars 0 1 2 3 4 5 6 7 8 9 10 Rice ($35B, 10% of $354B) Maize ($21B, 10.2% of $210B) Potato ($5.9B, 12.2% of $48.5B) Wheat ($5.8B, 7% of $82.3B) Tomatoes ($5.5B, 20.6% of $26.5B) Grapes ($4.8B, 12.5% of $38.6B) Sugarcane ($4.0B, 15.3% of $26.3B) Yams ($3.8B, 17.7% of $21.2B) Soybeans ($3.9B, 10.6% of $36.6B) Bananas ($3.2B, 19.7% of $16.0B) Cotton Lint ($2.5B, 10.7% of $23.0B) Oranges ($2.5B, 14.2% of $17.5B) Tobacco ($1.8B, 14.7% of $12.3B) Coconut Palm ($1.6B, 17.1% of $8.5B) Cassava ($1.5B, 8.4% of $22.0B) Sweet Potato ($1.4B, 10.2% of $12.5B) Green Coffee ($1.3B, 15% of $8.9B) Sugarbeet ($1.3B, 10.9% of $11.4B) Barley ($1.2B, 6.3% of $19.6B) Watermelon ($1.1B, 13.8% of $8.0B) Carrot ($1.0B, 22% of $4.5B) Pepper ($0.9, 12.2% of $7.5B) Melon ($0.9B, 13.8% of $6.5B) Strawberry ($0.6B, 10% of $6.1B) Sorghum ($0.5B, 6.9% of $7.9B) Crops 26-40 Combined ($4.2B, 10.5% of $39.9B) 17 species of nematode impact rice production worldwide Nematology

11. Nematodes:The major pathogen of some crops http://aes.missouri.edu/delta/research/soyloss.stm Nematology

12. Nematodes are different plant-pathogens(compared tobacteria, fungi, viruses) • Animals: • nervous system • behavior • environmental sensing • nematicide targets Nematology

13. Nematodes are different(compared tobacteria, fungi, viruses) • Animals: • nervous system • development • coupled to host • coupled to environment Nematology

14. Nematodes are different(compared tobacteria, fungi, viruses) • Animals: • nervous system • development • many protein-coding genes • nematode (C. elegans): 20,170 (ws187: January 2008) • (plant parasitic nematodes? Lecture7) • bacterium (M. genitalium): 483 • yeast (S. cerevisiae) 6,186 • fungal pathogen (M. grisae) 11,108 • insect (Drosophila): 14,108 (R5.8: May 2008) • mammal (human): ~20,500 (January, 2008) • plant (Arabidopsis): 27,235 (TAIR8: June, 2008) Nematology

15. Plant-parasitic nematodes:4 case studies • Sedentary endo-parasites: • Root-knot nematode • Meloidogyne spp. • Cyst nematode • Heterodera and Globodera spp. • Migratory endo-parasite: • Lesion nematode • Pratylenchus spp. • Insect vectored nematode • Pine wilt nematode • Bursaphelenchus • Lecture 8: The world of plant-parasitic nematodes. Nematology

16. Root-knot nematode (RKN) Meloidogyne spp. • Classic root galling phenotype • Galls • 3-7 giant cells at the core • expansion/division of surrounding cells Nematology

17. RKN • ~ 80 described species, distributed worldwide in temperate and tropical agriculture • obligate parasites of essentially all vascular plants • but individual spp./isolates may have restricted host range • duration of life-cycle depends on spp. and temp. • M. incognita on tomato @ 29°C: • adult females develop ~13–15 days after root penetration • egg laying ~ 6 days later; continues 2–3 months Nematology

18. RKN life cycle Nematology

19. Symptoms… • Amount of galling… • host plant species/cultivar: • Carrots typically undergo severe forking with galling predominantly found on lateral roots • RKN galls on lettuce are beadlike • On grasses and onions, galls usually small and barely noticeable Resistant and susceptible lettuce Nematology

20. Symptoms… • Amount of galling depends on: • host plant species/cultivar • nematode population density • more worms > more galls • more worms > larger galls (multiple nematodes/gall) • Meloidogyne species/race • e.g., M. hapla produces galls less than half the size of those produced by M. incognita on the same plant hosts. Nematology

21. Symptoms… Galls on cucumber roots Galls on ligustrum roots Galled potato Carrots Nematology

22. Symptoms… • Stunted or decline symptoms occur in patches rather than as a overall decline of plants within an entire field Nematology

23. Case study 2: Cyst nematodes • Two important genera • Heterodera • Heterodera avenae: Cereal cyst nematode • Heterodera glycines: Soybean cyst nematode (SCN) • Heterodera schachtii: Beet cyst nematode • etc • Globodera • Globodera pallida: Potato cyst nematode (PCN) • Globodera rostochiensis: Potato cyst nematode • Globodera tabacum: Tobacco cyst nematode • etc • Restricted host ranges • Major pathogens • SCN infests every soybean-producing state in the U.S. • total soybean yield loss estimates approaching $1 billion per year • PCN recently discovered in Idaho Nematology

24. Nematology

25. Cysts Nematology

26. Cyst nematode life cycle Nematology

27. SCN symptoms • Termed “soybean yellow dwarf” disease • Responsible for ~50% of all pathogen related yield loss • Resistant cultivars available (but not stable) • feeding females obvious on roots Nematology

28. Case study 3: Lesion nematode • Pratylenchus spp. • ~70 species attack >400 host plants • potato, peanut, monocots, fruits • Migratory endoparasites • Herbivores: cause massive physical damage • Population density of 3,000 worms/gram of root possible • Overwinter in root debris as J4 Nematology

29. Symptoms Corn roots Peanut • “destructive” feeders cause lesions • predispose the plant to fungal infection • disease typically in patches • control • pre-plant fumigation • post-plant nematacides • good sanitation to avoid infestation Nematology

30. Case study 4: Bursaphelenchus • Causative agent of pine wilt disease • kills trees in less than a month • mechanism: • worms feed on cells surrounding resin ducts • resin to leak into the tracheids • tracheid cavitation (air pockets) ensues • transpiration cannot be sustained • nematodes vectored by pine sawyer beetles • Monochamus spp. Nematology

31. Pine wilt disease • Scots pine is the most susceptible tree species • Distribution • US • especially mid-west • discovered 1979 • Asia • especially Japan • Control • Choice of unsusceptible trees, including: • balsam fir, eastern red cedar, piñon pine, lodgepole pine, limber pine, ponderosa pine, Balkan pine, Virginia pine, Douglas fir, eastern hemlock, etc. • Destruction of infected trees • Sanitation to avoid infestation • B. xylophilus is a quarantine organism in the EU • Chemical control of beetles not practical Nematology

32. PPN identification Nematology

33. Nematology

34. Nematology

35. Fumigant nematacides Nematology

36. Non-fumigant nematacides Nematology

37. “Natural” nematacides Nematology

38. Future control??? • New nematacides • traditional screens • rational design from genomic approaches • Identification/introgression of natural resistance • marker assisted breeding • Transgenic resistance • move natural R-loci across species boundaries • e.g., Tomato Mi confers RKN resistance in eggplant (but not tobacco) • mimic natural resistance • induce death of giant cells/syncytia • use the feeding site to deliver an anti-nematode agent • RNAi a nematode gene Nematology