DISEASE CAUSING ORGANSIMS Reading Text: Chapter 10. tomvolkfungi forestpathology/fungi.html

1. DISEASE CAUSING ORGANSIMS Reading Text: Chapter 10. http://tomvolkfungi.net http://www.forestpathology.org/fungi.html

2. Pathogens • Fungi and fungal-like organisms • Viruses, viroids, and prions • Bacteria • Phytoplasmas • Nematodes • Parasitic plants • Protozoans

5. DOMAINS AND KINGDOMS

6. Tree of Life

7. FEATURES OF FUNGI AND FUNGAL-LIKE ORGANISMS Kingdom Phyla Features Hyphae Cell walls Spores Sexual Asexual Straminipila Oomycota no septa glucans/cellulose Oospores zoospores (Chromista) (fungal-like) Mycota (Fungi) (True fungi) Zygomycota no septa glucans/chitin Zygospores sporangiospores Glomeromycota no septa None yes Ascomycota septa glucans/mannans Ascospores conidia Basidiomycota septa glucans/mannans Basidiospores conidia, (with (rarely) clamps) Deuteromycota septa glucans/mannans None conidia

8. Phyla Role Oomycota Damping off, feeder (fine) root diseases Zygomycota Saprophyte, endomycorrhizal fungi, few pathogens (storage molds) Glomeromycota Arbuscular (endomycorrhizal fungi) Ascomycota Saprophyte, ectomycorrhizal fungi, (Deuteromycota) foliage diseases, cankers, vascular wilts, fine root diseases, powdery mildews, stain fungi Basidiomycota Saprophytes, ectomycorrhizal fungi, stem and branch decays, structural root diseases, rusts

9. Out of the 80,000 -120,000 described fungal species only about 10% are plant pathogens. There may be as many as 1.5 million fungal species.

10. Features of fungi The vegetative body of fungi is the mycelium (made up of thread-like hyphae) which grow through or on substrates. Fungi disperse widely by spores which can be either asexual or sexual. The most commonly produced spores are asexual conidia or conidiopsores. Other asexual spores are sporangiospores. Sexual spores include zygospores, ascospores and basidiospores; they are produced in fruiting bodies. Spores can be airborne, spread by rain splash or water or by insects, other animals and humans. Oomycota were once included in the Fungi but are now in the Kingdom Straminipila (Chromista). Oomycota have asexual spores (zoospores) and sexual spores (Oospores). Many fungi have resting stages - chlamydospores or sclerotia

13. Nectria perithecia Peziza apothecia Ascomycota

15. Rhytisma tar spot on maple – Ascospore production

16. Nectria Canker – Ascomycota

17. Basidiomycete hyphae showing clamp connections. Also associated yeast cells and bacteria Basidiomycete hyphae decaying wood cells – clamp connections and Ca oxalate crystals

18. Different Basidiomycota

19. White Pine Blister Rust – Basidiomycota

20. OOMYCOTA LIFE CYCLE

21. Pathogens other than fungi Viruses, viroids, and prions Bacteria Phytoplasmas Nematodes Parasitic plants Protozoans

22. Viruses – protein coat and nucleic acid Viroid – low MW RNA Prion – infectious protein molecule Viruses, viroids andprions

23. Viruses and viroids • Need a vector • Insects • Nematodes • Grafting or vegetative propagation • Can move through plant in phloem or xylem, or stay localized in foliage • Can become part of plant genome

24. Camelia mosaic virus

25. Bacteria • 1-celled prokaryotes with a cell wall • Rods (bacilli), spirals, or spherical (cocci) • Easily exchange genetic material on plasmids

26. Symptoms • Bacteria cause disease by enzymes that digest cell walls, toxins, or tumors • Typical symptoms are: • Water soaking • Wetwood • Shoot blight • Bleeding cankers • Galls

27. Phytoplasmas • Also called MLO’s, or Mycoplasm-like organisms • Like bacteria without cell walls • Cannot be cultured apart from the host

28. Nematodes • Worm-likeanimals in Phylum Nemahelminthes • Various parasitic habits • Usually in the soil or on roots, more of an issue in agriculture " If all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable..."-N.A. Cobb, 1914

29. Pine Wilt Nematode • Bursaphelenchus xylophilus, vectored by Monochamus sp. (Cerambycidae) • Introduced to Asia from North America

30. Parasitic Plants Evolution towards parasitism has occurred at least 8 times in the flowering plants. Many are in the order Santalales: • Loranthaceae – leafy mistletoes • Santalaceae – root and stem hemiparasites • Viscaceae • Phoradendron – leafy mistletoes • Arceuthobium – dwarf mistletoes

31. True Mistletoes • Phoradendron spp. - • Common on oaks • South of 40-45 lat. • Cause water stress, usually not lethal • Spread by birds

32. Dwarf Mistletoes • Arceuthobium spp. • Host-specific • Conifer hosts • Dioecious • Sticky seeds spread by birds or forcefully ejected from plant

33. Symptoms • Parasitic plants are usually visible • Brooming • Galls • Reduced growth

34. Protozoans such as phytoflagellates can parasitize milkweed, tomato, onion and chive plants.