1. Abiotic Plant Problems Biotic Plant Problems (Plant Diseases) Disease Triangle Plant Pathogens: Bacteria, Fungi, Oomycota, Viruses, Viroids, Nematodes Abiotic vs. Biotic Plant Problems Discuss: Photos used from various UF/IFAS Extension Publications or provided by UF/IFAS faculty and staff, unless otherwise stated 1

2. Abiotic Plant Problems Abiotic plant problems are caused by environmental factors, either natural or man-made non-infectious, non-living (abiotic = without life) Unfavorable soil properties or structure Nutrient imbalances Moisture extremes Temperature extremes Light extremes Physical injuries Chemical toxicity And in Florida, lightning strikes! 2

3. Abiotic Human Problems Vitamin deficiencies Cholesterol imbalances Mercury or lead poisoning Broken bones Burns Allergic Reaction Others? 3

4. Abiotic Plant Problems Can kill plants Can predispose plants to infection by plant pathogens Can be natural, such as temperature extremes Can be due to human activity, such as improper use of fertilizers or pesticides It is common to have both biotic and abiotic problems affecting plant at same time, independently! 4

5. Lightning strikes Car or lawn equipment exhaust Animals - moles, armadillos, urine Abiotic: Physical Injuries 5

6. Abiotic: Cold Temperatures 6

7. Abiotic: Plants can be sunburned too – not just tourists! 7

8. Abiotic: Excess Water Oedema: little pimples form on leaf; roots taking up water faster than plant can use or transpire T. Broschat, UF/IFAS/FLREC 8

9. Abiotic: Low Soil Moisture 9

10. Abiotic: Nutrient Deficiency Tomato: Calcium Sunflower: Iron Palm: Potassium Celosia: Manganese Citrus: Zinc Palm: Manganese Photos from various UF/IFAS Extension Publications 10

11. Abiotic: Chemical Damage Herbicide damage Excessive iron chelete applied to soil Herbicide damage 11

12. Biotic Plant Problems Biotic plant problems or diseases require a second organism that will infect the plant and disrupt its normal appearance and growth – infectious, living 12

13. Plant Disease Triangle Susceptible Host Immunity or resistance is the rule for plants Some plant pathogens are very host specific; others have a wide host range Pathogen Pathogens are not found “everywhere” Favorable Environment All the environmental factors surrounding the host and pathogen may help the pathogen infect the host and determine the severity of disease development. 13

14. Plant Disease Triangle Susceptible Host DISEASE Pathogen Favorable Environment 14

15. Plant Disease Triangle Pathogen Susceptible Host Favorable Environment X Pathogen Favorable Environment X Pathogen Favorable Environment X NO Disease 15

16. Plant Pathogens Fungi Oomycetes Bacteria (including fastidious bacteria) Viruses and Viroids Nematodes 16

17. Fungi and Oomycetes Oomycetes used to be considered a family within the Kingdom Fungi Fungi now considered more closely related to animals than Oomycetes Oomycetes now considered more closely related to plants and algae Both fungi and Oomycetes are eukaryotes that digest food externally and absorb nutrients directly through their cell walls 17

18. Heterotroph: obtain carbon and energy from other organisms Biotroph: obtain nutrients from living host Saprotroph (saprophyte, saprobe): obtain nutrients from dead host Nectrotroph: infect a living host, then kill host cells to obtain nutrients Obligate: can only grown in association with its host plant (can’t grow on artificial media) Fungi and Oomycetes Life styles: 18

19. CharacterOomycotaTrue Fungi Sexual reproduction Heterogametangia; Fertilization of oospheres by nuclei from antheridia forming oospores. Oospores not produced; Sexual reproduction results in zygospores, ascospores or basidiospores Nuclear state of vegetative mycelium DiploidHaploid or dikaryotic Cell wall compositionBeta glucans, cellulose Chitin; cellulose rarely present Type of flagella on zoospores, if produced Two types; one whiplash, directed posteriorly; the other fibrous, ciliated, directed anteriorly If flagellum produced, usually of only one type: posterior, whiplash MitochondriaWith tubular cristaeWith flattened cristae Fungi and Oomycota From: Why are Phytophthora and other Oomycota not true Fungi? By Amy Y. Rossman and Mary E. Palm http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/Oomycetes.aspx Also see: http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/IntroOomycetes.aspxhttp://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/IntroOomycetes.aspx19

20. https://www.youtube.com/watch?v=lB4QYN7dlgc https://www.youtube.com/watch?v=PxF8OwDtJh0&ebc=ANyPxKr- XPjQG4MBmaGz5uf5WqgjD3b5370YlqKjvvIxp1IOGGJso3YgDPyd2RI 8niluJ1hxA-ALaRk9ZdlDQk2P3tGWEQXIkw Phytophthora: Zoospores emerging from sporangium Zoospores attracted to root exudates and infecting the root Oomycota 20

21. Diseases caused by Oomycetes: Root rots of numerous plants Pythium spp. Late blight of potato and tomato Phytophthora infestans Downy mildew of grape and impatiens Plasmopara viticola – grapes Plasmopara obducens – impatiens Sudden oak death (Ramorum blight) killing oak species in CA Phytopthora ramorum 21

22. True Fungi Fun Fungal Factoids: About 99,000 known fungal species, and we add about 1,200 each year Most plant diseases (70%) are caused by fungi But, fewer than 10% of the known fungi cause plant diseases 22

23. True Fungi Fun Fungal Factoids: Plant pathogenic fungi are parasites, but not all plant parasitic fungi are pathogens!! Parasite obtains nutrients from a living host plant If causes disease with symptoms (disrupts normal growth and appearance of plant), parasite is a pathogen If simply depends on plant host for nutrition, parasite is either a beneficial symbiont or an endophyte 23

24. True Fungi Fun Fungal Factoids: Endophyte example: Neotyphodium (Ascomycota) – beneficial for landscape grasses (heat and water stress) but not beneficial for pasture grasses as fungus produces alkaloids that are bad for animals Beneficial symbiont examples: Mycorrhizae – root/fungal association Lichen – algal/fungal association 24

25. True Fungi http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages /IntroFungi.aspx Main fungal groups (phyla): Ascomycota Basidiomycota Chytridiomycota Zygomycota Glomeromycota (arbuscular mycorrhizae) Sixth one may be added 25

26. True Fungi Four phyla with plant pathogens: Ascomycota – most plant pathogens Basidiomycota – Rusts, Smuts and Rotters Chytridiomycota – pathogens and vectors of plant viruses Zygomycota – Mucor, Rhizopus – post-harvest diseases of fleshy fruits and vegetables 26

27. Ascomycota Fungi and Sex and Names If a fungus is reproducing without sex, spores produced are asexual spores = conidia, which come in all different sizes, shapes and colors If fungus is reproducing with sex, spores produced are sexual spores = ascospores Ascospores are produced in a saclike structure called an ascus Fungi often have two Latin names – one for the asexual stage and one for the sexual stage Some fungi only produce conidia; some fungi only produce ascopsores; some fungi produce both 27

28. Ascomycota: Sexual Spores By CarmelitaLevin - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=41198837 By CarmelitaLevin - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=41198109 Sordaria asci and ascosporesSerenomyces asci and ascospores 28 By Beth Des Jardin, UF/IFAS, FLREC

29. Ascomycota: Asexual Spores Lasiodiplodia Fusarium Exserohilum Cylindrocladium Pestalotiopsis Phomopsis 29 All photos by Beth Des Jardin, UF/IFAS, FLREC

30. Basidiomycota (Rusts, Smuts and Wood Rotters) can produce up to 5 different spore types can complete life cycle on one host, or some complete their life cycle on two hosts devastating diseases that humans have dealt with since they started cultivating crops (wheat, etc.) we are still trying to manage these diseases, primarily by breeding for resistance https://www.youtube.com/watch?v=AeuP5IYP5HA Life cycle of wheat stem rust Rusts 30

31. By Boom10ful (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/ by-sa/4.0)], via Wikimedia Commons By Rasbak (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons Jim Plaskowitz, USDA/ARS, Public Domain Tilletia indica Karnal Bunt basidiospore Ustilago maydis Corn Smut Huitlacoche Ustilago nuda Loose Smut Basidiomycota (Rusts, Smuts and Wood Rotters) Smuts 31

32. Basidiomycota (Rusts, Smuts and Wood Rotters) Wood Rotters Ganoderma zonatum Ganoderma Butt Rot Armillaria tabescens Armillaria Root Rot 32

33. Chytridiomycota By USDA-APHIS-PPQ - USDA-APHIS-PPQ Agence canadienne d'inspection des aliments, Public Domain, https://commons.wikimedia.org/w/index.php?curid=5603175 Synchytrium endobioticum Black Wart Disease of Potato Olpidium brassicae transmits a virus that causes Lettuce Big Vein include pathogens and a vector of a plant virus obligate fungi Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org 33

34. Bacteria  Bacteria do not cause nearly as many diseases as fungi or viruses plant pathogens include both gram-positive and gram-negative bacteria easily grow on artificial media many species are subdivided into pathovars, indicating distinctive pathogenicity to one or more plant hosts http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/Bacteria.aspx34

35. Bacteria  Fastidious Bacteria all are vascular colonizers vectored by insects very difficult to grow artificially, if at all group without cell walls: phytoplasma – phloem-limited; Candidatus Phytoplasma palmae spiroplasma – phloem-limited; Spiroplasma kunkelii group with cell walls: phloem-limited bacteria - Candidatus Liberobacter asiaticum (=Huanglongbing pathogen) xylem-limited bacteria - Xylella fastidiosa http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/Fastidious.aspx35

36. Bacteria Fastidious bacteria are very small Spiroplasma Xylella Phytoplasma 36

37. Viruses http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/PlantViruses.aspx http://plantpath.ifas.ufl.edu/plant-virus-profiles/# are non-cellular; assemble themselves mature virus particles are dormant they come “alive” and reproduce only inside infected cells – obligate parasites virus particles (virions) composed of: genome (nucleic acid) – ss+RNA, ss-RNA, dsDNA protein protective shell (capsid) some enveloped within lipoprotein membrane 37

38. Viruses range from 30 nm diameter (spherical viruses) to 2 µm (filamentous viruses) 38 McGraw-Hill Concise Encyclopedia of Bioscience. S.v. "Plant viruses and viroids." Retrieved May 21 2016 from http://encyclopedia2.thefreedictionary.com/Plant+viruses+and+viroids http://encyclopedia2.thefreedictionary.com/Plant+viruses+and+viroids

39. Viruses immobile – rely on other organisms to be moved around from plant to plant passive transmission – mechanically, vegetative propagation (cuttings) or seed active transmission requires vector plant-feeding arthropods, especially aphids and whiteflies nematodes plant-parasitic fungi 39

40. Viroids naked, infectious RNA – no protein coat genomes between 246-375 nucleotides do not produce any proteins when they infect a plant cell use the host cell RNA polymerase to reproduce their RNA and move into other plant cells spread through vegetative propagation, mechanical contamination, pollen and seed; vectors not necessary http://www.apsnet.org/publications/apsnetfeatures/Pages/Viroids.aspx40

41. Viroids They may be small, but the diseases can still be devastating! Cadang-Cadang is a viroid disease of coconut palms that has destroyed over 30 million palms in the Philippines Potato spindle tuber viroid is model pathogen http://www.apsnet.org/edcenter/intropp/lessons/viruses/Pages/PotatoSpindleTuber.aspx 41

42. Nematodes http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/IntroNematodes.aspx are roundworms (multicellular animals) most are free-living (40%) – feed on bacteria, fungi, protozoans and other nematodes but, many are parasites of animals (44%) and plants (15%) need water (even if minimal) Caenorhabditis elegans – bacterial- feeding nematode (not plant parasitic) http://www.apsnet.org/EDCENTER/K-12/NEWSVIEWS/Pages/Nematodes.aspx42

43. Nematodes Plant Parasitic Nematodes: have a hollow mouth spear called a stylet stylet connected to pharynx, which is connected to the intestine stylet used to puncture plant cells, withdraw food, and secrete protein and metabolites that aid the nematode in parasitizing the plant Endoparasitic Ectoparasitic Nematode Human Hair 43

44. YOU Which Plant Pathogen Are YOU? Bacteria, Fungi, Oomycota, Viruses, Viroids, Nematodes 4444

45. 45 This is based on the American Society for Microbiology's educational activity, What Microbe Are You? A full lesson plan for the ASM activity can be found online: www.asm.org/index.php/educators/k-12-classroom- activities/23-education/k-12-teachers/8214-what-microbe- are-you Which Plant Pathogen Are You? is a "personality quiz" aimed at engaging audiences and creating awareness about plant pathology. It can also be used as an ice- breaker or classroom activity.

46. YOU Which Plant Pathogen Are YOU? 46 #16 I am... Phytophthora capsici Spots, rots and blights I am a fungus-like pathogen (oomycete) that loves my fruits and veggies - except lima beans. Wet, humid conditions help me thrive. I can cause seed rots, seedling blights, leaf spots, fruit rots – look at this zucchini: Photo: UF/IFAS, PP176 Oomycota Electronic Data Information System (EDIS) http://edis.ifas.ufl.edu 46

47. YOU Which Plant Pathogen Are YOU? 47 #16 I am... Phytophthora capsici Spots, rots and blights I am a fungus-like pathogen (oomycete) that loves my fruits and veggies - except lima beans. Wet, humid conditions help me thrive. I can cause seed rots, seedling blights, leaf spots, fruit rots – look at this zucchini: Photo: UF/IFAS, PP176 Oomycota 47 30 cards, each with a different pathogen Many, but not all, have an EDIS document that a you can refer to for more information EDIS publications are reviewed at least every 3 years to keep the information up to date Photos can be used from EDIS documents, but please acknowledge the source.

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