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PLANT PATHOLOGY. Plant disease Plant’s normal function is interrupted by a pathogen or the environment.

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Presentation on theme: "PLANT PATHOLOGY. Plant disease Plant’s normal function is interrupted by a pathogen or the environment."— Presentation transcript:

1 PLANT PATHOLOGY

2 Plant disease Plant’s normal function is interrupted by a pathogen or the environment

3 Plant disease  Is this a disease?

4 Biotic damage Caused by living pathogens or parasites

5 Biotic damage Symptoms: visible expressions of plant reaction to the pathogen

6 Biotic damage Signs: indications of disease from direct visibility of a pathogen –Actually seeing the pathogen

7 DISEASE TRIANGLE  Disease needs all three to develop –Only need to block one of them

8 Pathogen Organisms capable of causing disease  Fungus  Bacteria  Virus  Other micro-organisms

9 Pathogen Parasites: obtain food from living organisms (host)

10 Pathogen Obligate parasite: require (obligated to) living plant cells as food to complete life cycle

11 Pathogen Facultative parasite: obtain nutrition from either living or dead plants

12 Pathogen Saprophyte: feeds on dead organic material on plant or in soil

13 HOST Susceptible: no ability to retard or resist disease  Susceptible plant tissue –Fertilization

14 HOST Resistance: some ability to retard or tolerate disease

15 HOST Immunity: complete resistance against disease

16 ENVIRONMENT Moisture and temperature are the predominant factors

17 ENVIRONMENT Moisture, water is critical  Dry springs can reduce disease occurrence  Often 24 to 48 hours continually wetness required  Poor irrigation practice

18 ENVIRONMENT Temperature, each pathogen has optimal range  Predisposed condition of host  Host is stressed, can’t defend

19 FUNGUS  The vast majority of plant diseases are fungal

20 FUNGUS What is a fungus?  Microscopic organisms that lack chlorophyll, cannot produce own food  Multicellular organism that is threadlike in composition

21 FUNGUS Enormous genetic variability due to rapid reproduction

22 FUNGUS Species of fungi are subdivided into strains that are very specific in  Plant species or cultivars  Virulence  Temperature range  Moisture requirements

23 SPORE  Fungal seed  Very distinct shape and size used to differentiate pathogens  Single celled or multi-celled

24 SPORE Asexual, not requiring the union of sexual parts to be produced  Conidia

25 SPORE  Sexual, requiring union of sexual parts to be produced –Basidiospore, ascospore, oospore…

26 SPORE Where do you see spores when a plant is infected?  Leaf surface –Appears as mold (powdery mildew)

27 SPORE Where do you see spores when a plant is infected?  Fungal fruiting bodies  Spore producing pockets  Sporodochium, acervulus, pycnidium…

28 HYPHAE Hyphae is what germinates out of the spore  Branches out into tubular filaments

29 HYPHAE Mycelium refers to all the hyphae as a whole, as the fungal body  Inside the plant, or outside the plant under high moisture

30 PLANT INVASION Fungus enters plant through any of the following  Wounds –Mechanical, pruning or handling

31 PLANT INVASION Wounds –Insects, vectors or egg laying

32 PLANT INVASION Wounds –Naturally occurring  Secondary roots rupture the main root when emerging  Leaf scars

33 PLANT INVASION Fungus enters plant through any of the following  Natural openings –Lenticels

34 PLANT INVASION Fungus enters plant through any of the following  Direct penetration –Pushing through tissue –Resistance can come in the form of thicker cuticle or hairy leaf

35 FUNGAL LIFE CYCLE Peach brown rot is used as an example

36 FUNGAL LIFE CYCLE Overwinter, Disease is dormant in infected fruit and stems

37 FUNGAL LIFE CYCLE Dissemination Disease produces spores (conidia) that are spread by wind and rain

38 FUNGAL LIFE CYCLE Inoculation Spores contact susceptible blooms

39 FUNGAL LIFE CYCLE Penetration Spore germinates and enters tissue directly

40 FUNGAL LIFE CYCLE Infection Establishes hyphae in tissue and feeds on cells

41 FUNGAL LIFE CYCLE Incubation period Time between infection and appearance of symptoms

42 FUNGAL LIFE CYCLE Invasion Spreads from bloom to other parts of the plant within tissue

43 FUNGAL LIFE CYCLE Dissemination…

44 FUNGAL LIFE CYCLE Overwinter When temperature cools, fungus goes dormant

45 Zombie Fungus  uffingtonpost.com/2011/0 9/14/zombie- caterpillars- virus_n_ html uffingtonpost.com/2011/0 9/14/zombie- caterpillars- virus_n_ html uffingtonpost.com/2011/0 9/14/zombie- caterpillars- virus_n_ html  Brazilian rain forest  Controls ants

46  Infection pegs grow from body  Shoots at passing ants

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