disease triangle - created from Mind Map

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pathogen

virulence

environment

conducive

host

suscepitable

stages in plant disease development and disease cycle

1st stage: Inoculation

Initial contact of a pathogen with a site of plant where infectcion is possible.

2nd stage: Pre-penetration

3rd stage: Penetration

4th stage: Invasion

5th stage:colonization

growth and reproduction of the pathogen in or on infected tissues

successful colonization results in the appearence of symptoms

Infection Process in Fungi

inoculum

any part of teh pathogen that can initiate infection

types of inoculum

primary inoculum

secondary inoculum

fungi

bacteria,mollicutes,protozoa,viruses or viroids

nematodes

spores,sclerotia or hyphae

recognition

recognition between host and pathogen

spore attachment and germination

hatching nematode eggs

direct penetration

direct penetration through intact plant surfaces

through wounds

through natural opening

fungi

nematode

fungi

bacteria

mollicutes

viruses and viroid

stoma

hydathode

open pores at margins and tips of leaves

nectarthode&lenticels

opening on fruits, stems,tubers

----less efficient

fungi and bacteria

fungi

bacteria

produce intra-&intercellualr mycelium or haustoria

some invade xylem vessels

invade inter-&intracellular host tissues

xylem vessels

symptom

all visible and detectable changes in the infected plants

slow

fast

2-3 years after inoculation

diseases caused by viruses and mollicutes

2-4days after inoculation

localized viral diseases

pre-penetration

penetration

post-penetration

1. Inoculation

2. Attachment

spore adherence to plant surface

requires mucilage substances

3. Spore germination

requires stimulation

germ tube formation & extension

5.Appressorium formatio

contains lipids,polysaccharides and proteins

some contain melanin (dark brown pigment)

high turgor pressure due to accumulation of glycerol

function:to puncture plant cuticle using penetration peg

4. Growth of germ tube

6.Penetration of host cells

8.Diseases symptom appearence

9. Dissemination of inoculum

10. Pathogen death

7.Colonization

IM

ITE

haustoria