2. Summary Success of pathogen:survival structures, saprotrophic ability,host-specialization, phylogenetic distance, similar ecology of hosts Severity of epidemic: density of hosts, environment, genetics of host Resistance in host: present/absent, metapopulation structure

3. Summary-2 RED QUEEN HYPOTHESIS Genetic variability/genetic structure. Population size Generation time Increased virulence linked to trade offs

4. Summary-3 SIGNS SYMPTOMS

5. And of course… fungi Fungi: saprophytic, symbionts, and pathogens Polyphyletic group in evolutionary terms –Basidiomycetes Ascomycetes Zygomycets Animals Plants Red algae Brown algae Myxomycetes

7. Diversity of fungi, but all have ideal structure for plant infection: –hypha/cord/rhizomorph/infection peg/appressorium –Sexual vs. asexual reproduction: can do both –Do not photosynthesize –Chitin in cell wall –Exogenous digestion –Indefinite growth –Phenotypic plasticity and pleomorphisms

10. Fungi do not photosynthesize Biotrophic: mycorrhyzae, rusts Endophites: clavicipetaceae, Necrotrophic; most pathogens Saprobes: primary (involved in litter decomposition)

11. Septa Pores CELLS

12. Thanks to their web-like indefinite growth in soil and plant substrates and their way of digesting nutrients fungi play a critical role in recycling nutrients which can then be reutilized by plants

14. Fungi like this one will actually decay the woody matter and physically free space for new generations of trees, besides recycling the nutrients

15. The weblike structure of fungi, usually immersed in the soil or in plant matter is involved in an essential symbiosis that greatly enhances the ability of plants to grow The weblike structure of fungi, usually immersed in the soil or in plant matter is involved in an essential symbiosis that greatly enhances the ability of plants to grow piant fungus

16. The visible part of root tips of most trees is actually a mantle of fungal hyphae fused with the plant tissue

17. What is the deal of this mutualism? Fungus absorbs nutrients for plants Plant gives fungus carbohydrates it produces via photosynthesis

18. There are thousands of mycorrhzial fungal species, and only at times do they produce the classical fruit body (e.g.mushrooms) above ground In absence of fruit body: how can we identify them?

19. DNA can be extracted from any part of an organism, like the web-like hyphae emanating from this root tip DNA sequence identified these threads as Tricholoma matsutake

20. Fungi… again! ASCOASCOMYCETES BASIDIOBASIDIOMYCETES OOMYCETES (fungus-like, water molds)

21. ASCO ASCOMYCETES Yeasts (fermentation, human mycoses)Yeasts (fermentation, human mycoses) Truffles, morelsTruffles, morels Penicillia (penicillin), Fusaria (potent toxins, damping off of seedlings), molds

22. Ascus is the sack in which the spores are contained

23. Asci can be placed on a disk (apothecium), many apothecia can be together in a fruitbody Morel fruitbody

25. Asci can be carried inside a flask (perithecium) Nectria

26. Ploidy is mostly n

27. BASIDIO BASIDIOMYCETES Mushrooms. mycorrhizalMushrooms. mycorrhizal Wood decay organismsWood decay organisms Rusts, Smuts Yeasts and damping off

28. Toadstools and huitacochle are both basidiomycetes

29. Basidium means “club”, it carries the basidiospores (dispersion propagules) naked

32. Most of their life, they are n+n (dikaryons), some rare ones are diploid

33. Oomycetes Belong to the kingdom Stramenopila, used to be called Chromista Phytophthora, Pythium, Saprolegnia H20H20

34. Oomycetes are not fungi Cellulose in cell wall Ploidy is 2n Result of sexual activity is oospore (2n) Meiosis, somatogamy, caryogamy all occur at the same time Water adapted biology, flagellate phase No septa, holocoenocytic hyphae Chitin in cell wall Ploidy is n, or n+n Result of sexual activity is a spore n Meiosis, somatogamy,caryogamy are usually interupted by vegetative (somatic phase) Better adapted for aerial transmission Septate hyphae

35. Phytophthora Some important plant pathogens, with very well known history –Phytophthora infestans and the Irish potato famine –Phytopthora cinnamomi and the Jarrah dieback in Australia

36. The Irish Potato Famine From 1845 to 1850 Phytophthora infestans Resulted in the death of 750,000 Emigration of over 2 million, mainly to the United States.

37. Phytophthora: “plant destructor” Best known pathogen whose long-distance transport linked to agriculture. –Infected root-stocks –Infested soil –Infected plants

38. 70 species of Phytophthora 60 until a few years ago, research accelerated, especially by molecular analyses Differentiated on basis of: –Type of sexual intercourse –Type of sexual activity –Number of hosts –Ideal temperature –Type of biology –Evolutionary history (Waterhouse-Cooke)

39. Hyphae, sporangia, and zoospores of P. ramorum

40. Zoospore

41. Most of their lifecycle they are 2n Have cellulose in cell wall Not fungi!!, but look like them because of convergent evolution

42. Human activities affecting disease incidence in forests Introduction of exotic pathogens Planting trees in inappropriate sites Changing stand density, age structure, composition, fire frequency Wound creation Pollution, etc.

44. Effects of fire exclusion

45. Effects of diseases on host mortality, growth and reproduction Young plants killed before reaching reproductive age Affect reproductive output Directly affect flowers and fruits

46. WGR

47. Complexity of forest diseases At the individual tree level: 3 dimensional At the landscape level” host diversity, microclimates, etc. At the temporal level

48. Complexity of forest diseases Primary vs. secondary Introduced vs. native Air-dispersed vs. splash-dispersed, vs. animal vectored Root disease vs. stem. vs. wilt, foliar Systemic or localized

49. Progression of cankers Older canker with dry seep Hypoxylon, a secondary sapwood decayer will appear

50. Root disease center in true fir caused by H. annosum

53. Categories of wild plant diseases Seed decay Seedling diseases Foliage diseases Systemic infections Parasitic plants Cankers, wilts, and diebacks Root and butt rots Floral diseases

54. Seed diseases Up to 88% mortality in tropical Uganda More significant when seed production is episodic

55. Stress cone cropBS on DF

56. Seedling diseases Specific diseases, but also diseases of adult trees can affect seedlings Pythium, Phytophthora, Rhizoctonia, Fusarium are the three most important ones Pre- vs. post-emergence Impact: up to 65% mortality in black cherry. These diseases build up in litter Shady and moist environment is very conducive to these diseases

57. Foliar diseases In general they reduce photosynthetic ability by reducing leaf area. At times this reduction is actually beneficial Problem is accentuated in the case of small plants and in the case other health issues are superimposed Often, e.g. with anthracnose,needle cast and rust diseases leaves are point of entry for twig and branch infection with permanent damage inflicted

60. Systemic infections Viral? Phytoplasmas Peronospora and smuts can lead to over 50% mortality Endophytism: usually considered beneficial

61. Grass endophytes Clavicipetaceae and grasses, e.g. tall fescue Mutualism: antiherbivory, protection from drought, increased productivity Classic example of coevolutionary development: Epichloe infects “flowers” of sexually reproducing fescue, Neotyphodium is vertically transmitted in species whose sexual reproductive ability has been aborted

62. Parasitic plants True (Phoradendron) and dwarf mistletoe (Arceuthobium) Effects: –Up to 65% reduction in growth (Douglas-fir) –3-4 fold mortality rate increase –Reduced seed and cone production Problem accentuated in multistoried uneven aged forests

66. Cankers, wilts, and die-backs Includes extremely aggressive, often easy to import tree diseases: pine pitch canker, Dutch elm disease, Chestnut blight, White pine blister rust Lethal in most cases, generally narrow host range with the exception of Sudden Oak Death

67. Root diseases Extremely common, probably represent the most economically damaging type of diseases Effects: tree mortality (direct and indirect), cull, effect on forest structure, effect on composition, stand density, growth rate Heterobasidion, Armillaria, Phellinus weirii, Phytophthora cinnamomi

72. Floral diseases Pollinator vectored smut on silene offers an example of well known dynamic interaction in which pathogen drives genetic variability of hosts and is affected by environmental condition Puccinia monoica produces pseudoflowers that mimic real flowers. Effects: reduction in seed production, reduction in pollinators visits

74. POPULATION DYNAMICS Species interactions and diversity

75. Density-dependence Most diseases show positive density dependence Negative dependence likely to be linked to limited inoculum: e.g. vectors limited If pathogen is host-specific overall density may not be best parameter, but density of susceptible host/race In some cases opposite may be true especially if alternate hosts are taken into account

76. Counterweights to numerical effects Compensatory response of survival can exceed negative effect of pathogen “carry over” effects? –NEGATIVE: progeny of infected individuals less fit; –POSITIVE; progeny more resistant (shown with herbivory)

77. Disease and competition Competition normally is conducive to increased rates of disease: limited resources weaken hosts, contagion is easier Pathogens can actually cryptically drive competition, by disproportionally affecting one species and favoring another

78. Diseases and succession Soil feedbacks; normally it’s negative. Plants growing in their own soil repeatedly have higher mortality rate. This is the main reason for agricultural rotations and in natural systems ensures a trajectory towards maintaining diversity Phellinus weirii takes out Douglas fir and hemlock leaving room for alder

79. Janzen-Connol Regeneration near parents more at riak of becoming infected by disease because of proximity to mother (Botryosphaeria, Phytophthora spp.). Maintains spatial heterogeneity in tropical forests Effects are difficult to measure if there is little host diversity, not enough host-specificity on the pathogen side, and if periodic disturbances play an important role in the life of the ecosystem