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What is hyperplasia?
It is the abnormal increase in cell division giving rise to galls
What is hypertrophy?
An abnormal increase in cell size
Describe crown gall
- Caused by agrobacterium tumefaciens
- Mostly effect woody, perennial hosts, tree fruits and grapes
- Grasses are only plant to escape this disease
- Once infection occurs growth of the galls are independent of the bacterium
Symptoms of crown gall
- Disrupts nutrient and water flow
What are aerial crown galls?
Systemic infection of agrobacterium tumefaciens occurs when individual cells break off the gall and travel through the vascular tissue to other parts of the plant
How to control crown gall
- Rotation with non-host crop
- Avoid wounding of Plant and control root chewing insects
- Use disease free plants
- Active galls can be killed using bacticin
- A biological control agent called agrocin84 ( contains A. Radiobacter strainK84 dip rootstocks)
What is black knot ?
- Caused by dibotryon morbosum
- Infects prunus species
- Disease is limited to North America
- Swellings on twigs and branches
How to control black knot?
- Foliar application of fungicide in the spring
- Removal and destruction of galls
- Removal of native or weedy hosts near orchards
What are decay diseases?
- Disintegration of host tissues are a result of enzymatic activity of pathogen
- Most common enzyme are cellulases which degrade cellulose
- Pectinases which degrade pectin
Why does dibotryon morbosum belong to the phylum ascomycota?
- It makes ascospores in a pseudothecium
- The pseudothecia are embedded in a dark colored mass of fungal tissue called stroma
What are environmental conditions needed for D. Morbosum?
- Rain for the release of ascospores
- Temps 13-25C
Characterize soft rots
Watery disintegration of plant tissue followed by slimy masses and odors
What are plant pathogenic soft rot pathogens?
Are bacteria that infect and colonize plant tissue and in the process release extra cellular enzymes that degrade the plant tissue
Describe bacterial soft rot
- Infection by pectobacterium carotovorum
- Occurs in the field and post harvest
- Affects primarily vegetables
How to control bacterial soft rot?
- In crop:
- Avoid root wounding
- Start with healthy seed
- Post harvest:
- Cold storage
What are gram positive bacteria?
Bacteria that have a thick peptidoglcan and retain the crystal violet stain
What are gram negative bacteria?
They have an outer membrane with a thin peptidoglcan layer
What is a perthophyte?
Fungi that colonize dead tissue
What is white rot?
Is a wood decay disease characterized by the whitish color of the decayed wood that results from the removal of lignin
What is brown rot?
The decayed wood is a brownish color due to the removal of cellulose from the wood by the fungus.
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