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1st Quiz, Name, date

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1st Quiz, Name, date

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  1. 1st Quiz, Name, date • 1 Pick one of the following two: • A)What are some ecological roles played by native diseases? • B)What are the elements of the disease triangle? • 2 Pick one of the following two: • A) In the Gilbert review, several categories of forest diseases are described: can you name and briefly describe three? • B)- Pick one category of forest diseases and write a paragraph about it

  2. Summary of 1st class • Emergent diseases different from native diseases • Disease triangle • DNA information useful to track microbes

  3. “Roles of native diseases”: • Thin natural populations of trees • Optimal allocation of resources • Selection for a genetically diverse host population • Maintain tree ranges • Succession: nutrient cycling

  4. “Emergent diseases”:diseases on the rise • New introduced, exotic, organisms • Good gone bad: e.g. climate change or human activities trigger excessive pathogenicity of native organism

  5. DISEASE TRIANGLE Pathogen Host Environment

  6. “Emergent diseases”:1: host • New host-pathogen combinations: exotic hosts hosts planted off site

  7. Cypress canker by Seiridium cardinale • Pathogen was first described in California in the 20s. Later it was described in Italy where it started a serous epidemic of Italian cypress • Belief that pathogen is native to California: is that true and why is it then causing a significant disease in our state?

  8. Conidia of Seiridium cardinale observed by optical microscope and SEM

  9. Use of molecular genetics to resolve issue of origin of pathogen • Used a technique similar to the one used in human forensics • Native populations should comprise many different individuals genetically • Introduced populations should be genetically simpler because of bottleneck related to introduction events

  10. RESULTS: CA vs. Europe • California population diverse genetically= native to the state • European population show no diversity=introduced

  11. Fig. 3 Symptoms caused by Seiridium cardinale on Cupressus macrocarpa (above) and xCupressocyparisleylandii (right)

  12. Spread of the disease. Seiridium cardinale, a pandemic in progress…

  13. 99.3 73.9 61.5 70.2 60.8 65.5 66.3 98.6 66.1 66.5 66.5 100 Seiridium NJ tree IT=Italy GR=Greece NZ=New Zealand US=USA CH=Chile

  14. 5-B 2-B 3-A 11-B 21-B 8-A 19-B 9-na 6-B 4-B 15-A 16-B 1-B 17-A 18-B 13 20-A/B 14-A 46 12-A 30 37 26 39 35 32 33 41 43 38 28 23 7 45 25 24 44 34 29 31 36 40 42 27 22 10-na 30 Node scaling Small: singleton MGs Medium: 2-5 indivs with same MG Large: 30 indivs with same MG Dark blue = Italy only Mid blue = Italy and other MED country Light blue = Only MED country, excluding Italy Black = Morocco Red = California A = clade A in NJ tree B = clade B in NJ tree na = no sequence available Seiridium cardinale – Minimum spanning network

  15. Results of coalescent analysis using MIGRATE-N Populations 1 = Greece 2 = Italy 3 = Cal Theta1 = 0.08826 Theta2 = 0.09727 Theta3 = 0.09735 M2-->1 = 347.450 M3-->1 = 6.392 M1-->2 = 23.160 M3-->2 = 6.886 M1-->3 = 5.142 M2-->3 = 6.180

  16. Why a disease in CA? • If pathogen is native to California, why is it causing such a serious disease? • We observed that disease incidence is variable with: • cypress species, • location,

  17. Range of susceptibility • Leyland cypress, Italian, monterey are listed as most susceptible • Arizona and McKnob are regarded as more resistant

  18. Range of susceptibility • 90% of Leyland are heavily infected • 10% of monterey • LEYLAND CYPRESS IS AN ORNAMENTAL CROSS, NOT NATIVE

  19. Range of susceptibility • Monterey is more susceptible in inland areas where it is NOT NATIVE: we believe that colder temperatures cause more wounds that lead to infection

  20. CONCLUSIONS • Cypress canker is a serious disease in Europe because pathogen was introduced • Cypress canker is a serious disease in California because hosts were introduced either through planting off range (Monterey cypress) or because host is artificial creation (Leyland cypress); extinction of LEYLAND is most likely

  21. “Emergent diseases”:2: environmental changes • Forestry and intensive forest use: timber production tree felling and creation of stumps fire exclusion and increase in density oversimplified forest composition changes in forest composition changes in forest structure

  22. Heterobasidion root disease • Heterobasidion (a bracket or shelf mushroom) infects trees through wounds and stumps, then it spreads through the roots to neighboring trees • With tree felling,stumps and wounds are created, suddenly exponentially increasing infection levels

  23. Heterobasidion shelf fruit-body

  24. Use of molecular genetics: • Differentiate Heterobasidion on fir/sequoias (H. occidentalis) from that on pine/junipers (H.irregularis) • Show that airborne meiospores are responsible for most infection of Heterobasidion • Show that in pines most infections start on stumps and that in true firs most infections on wounds

  25. True firs Pines Each spore is a genetically different individual: In pines we found the same genetic individual in stumps and adjacent trees indicating direct contagion between the two In true firs and true firs/sequoias we find same individual in adjacent standing trees indicating infection not linked to stumps but to wounds on standing trees

  26. CONCLUSIONS: • Logging activities increase Heterobasidion infection because of stump creation in pines and because of wounding in true firs sequoias • We have shown that in pine stumps H. irregularis and H. occidentalis can both be present and create a new hybrid entity • We have shown that in the past these hybridization events have lead to sharing of genes among these two species (Horizontal gene transfers)

  27. Armillaria root diseases • Armillaria, the honey mushroom, normally infects the roots of trees. It can be a saprobe and a pathogen and is common amongst oaks • If woodland composition shifts to pine/oak, pines become the target of attacks and gaps in canopy enlarge over time. Stress (e.g. flooding) exacerbates susceptibility

  28. Clusters of Armillaria

  29. How Does it Infect? • Two means of dispersal to other trees: • Mycelium can grow through direct root contacts and grafts with uninfected trees. • Rhizomorphs can grow through soil to contact uninfected trees. OAK or PINE DEAD OAK SOURCE:

  30. What are Rhizomorphs? SOURCE: • …“conglomerations of differentiated parallel hyphae with a protective melanized black rind on the outside.” • Rhizomorphs are able to transport food and nutrients long distances which allows the fungus to grow through nutrient poor areas located between large food sources such as stumps. SOURCE:

  31. Humongous Fungus It’s One of U-HAUL’s “Bizarre Roadside Attractions”

  32. CONCLUSIONS Human activities shifting from oak woodlands to mixed oak-pine lead to large mortality gaps in pines around oaks if honey mushroom is present CHANGING SPECIES COMPOSITION LEADS TO SEVERE DISEASE

  33. Many gaps with very little regeneration and have not closed in

  34. Change in gap area 1972-1999

  35. “Emergent diseases”:3: exotic pathogens • 99% of times human responsible for their introduction

  36. Like the conquistadores brought diseases that were lethal to those who had never been exposed to them, so do exotic diseases cause true devastation in plant communities because of lack of coevolution between hosts and microbes

  37. California invaded: 1849 A.D. Port Orford Cedar Root Disease 1950s New hybrid root pathogen 1990s Manzanita/madrone die-back Sudden Oak Death 1990s White pine blister rust 1930s Canker-stain of Sycamores 1980’s Dutch Elm Disease 1960s Pitch canker disease 1980s Oak root canker 2000

  38. How can people transport pathogens • By transporting plants and plant parts • Crops, and seeds • Raw food • Ornamental plants Untreated lumber Soil Insects vectoring fungi Military activity

  39. 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.

  40. What favors invasion of exotic fungi ? • Density of host increases severity of disease • Corridors linking natural habitats • Synchronicity between host susceptibility and pathogen life cycle • Ecological and environmental conditions

  41. Girdling aerial ‘cankers’ removed from roots

  42. Big Sur 2006 K. Frangioso

  43. P. ramorum absent P. ramorum present Wickland et al., unpublished

  44. P. ramorum growing in a Petri dish

  45. Organism new to science • Origin unknown • Biology unknown • Symptoms caused unknown • Immediately though highly regulated

  46. Rhododendron: In EU mostly a nursery issue, but also present in nurseries in US and Canada Stem canker Leaf necrosis