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DISEASES AND TREES

DISEASES AND TREES. What exactly is a disease? It is the outcome of an interaction between a plant and the environment, resulting in an altered physiology of the host Sustained interaction=biotic Single event= abiotic. What is a pathogen?.

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DISEASES AND TREES

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  1. DISEASES AND TREES • What exactly is a disease? It is the outcome of an interaction between a plant and the environment, resulting in an altered physiology of the host • Sustained interaction=biotic • Single event= abiotic

  2. What is a pathogen? • Strictly speaking a pathogen is the causal agent of disease • Bacteria • Viruses • Nematodes • Stramenopiles • Algae • Phytoplasmas • Higher plants

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

  4. Fungi… again! • Filamentous somatic (vegetative body) • High surface, good for extrogenous digestion • Good infection structures, infection peg, appressoria, rhizomorphs Chitin in cell wall Nuclear ploidy very unique Reproduction by spores: asexual mode very well represented Small nuclei, but with a lot of plasticity

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

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

  7. Some pathogen roles in natural plant communities • Selection of individuals best suited for the site • Maintenance of genetic diversity and stability in host plant populations • Establishment or maintenance of host geographic ranges • Natural succession • Regulation of stand density, structure, and composition

  8. DISEASE!! • Symptoms vs. signs; e.g. chlorosis vs. fruit-body • The disease triangle

  9. host-pathogen-environment • Susceptibility of individuals or of portions of individuals • Genetic variability • Basic compatibility (susceptibility) between host and pathogen • Ability to withstand physiological alterations

  10. Genetic resistance in host

  11. host-pathogen-environment • Basic compatibility with host (virulence) • Ability to maintain diversity: sex vs. no sex • Size of genetic pool • Agressiveness (pathogenicity) towards hosts • Ability to survive without host

  12. Chlamydospores of P. ramorum

  13. Pr75 Qa Monterey Pr87 Am Marin Pr86b Am Marin Pr86a Am Marin Pr84 Soil Marin Pr82 Vo Marin Pr80 Vo Marin Pr72 Rh Alameda Pr65 Qp Santa Cruz Pr58 Vo Marin Pr50 Qa Sonoma Pr201b Rh Santa Cruz Pr201a Rh Santa Cruz Pr47b Qa Sonoma Pr47a Qa Sonoma Pr35 Qa Sonoma Pr28 Ld Sonoma Pr24 Qa Sonoma Pr22 Qa Sonoma Pr20 Qa Sonoma Pr19 Qa Napa Pr16 Qa Santa Cruz Clone group Pr13 Qa Santa Cruz Pr11b Qa Monterey Pr11a Qa Monterey Pr10 Ld Monterey Pr08 Qa Napa Pr06 Qa Marin Pr05 Ld Marin Pr04 Qk Marin Pr03 Ld Marin Pr88 Uc Sonoma Pr89 Uc Sonoma Pr90 Qa Marin Pr91 Uc Sonoma Pr97 Qa Napa Pr102 Qa Marin Pr103 Ld Marin Pr104 Ld Marin Pr107 Uc Sonoma Pr110 Uc Marin Pr112 Uc Marin Pr113 Uc Marin Pr114 Uc Marin Pr115 Uc Marin Pr116 Uc Marin Pr136 Uc Marin Pr156 Ld Oregon Pr157 Ld Oregon Pr158 Ld Oregon PrJL3.1 Ss Sonoma PrSDC21.6 Ss Sonoma Pr36 Qa Sonoma Pr27 Qa Marin Pr57 Ld Santa Clara Pr70 Vo Marin Pr159 Ld Oregon 67 Pr52a Rh Santa Cruz Pr52b Rh Santa Cruz 89 PrCoen Rh Santa Cruz PrJL3.5.3 Ss Sonoma 96 Pr106 Uc Sonoma 93 Pr71 Qa Sonoma Pr01 Qa Marin PrE9/95 Rh Germany PrE16/99 Vb Germany 100 European group PrE12/98 Rh Germany PrE104 Water Germany PrE69082 Rh Germany PrE9/3 Water Germany PrE14/98-a Rh Germany Pl33 Cl Del Norte P. lateralis (outgroup) Pl16 Soil Josephine 0.1 Pl27 Tb Del Norte

  14. West Coast Europe P. lateralis

  15. host-pathogen-environment • Temperatures • Shading • Relative humidity • Free standing water • pH and any potentially predisposing factors • Nutrient status

  16. Colony diameter (mm) at 13 days

  17. Presence of free water Between 6 and 12 hours required for infection of bay leaves

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