Transcript Teleomorph vs Anamorph Nectria Fusarium perithecia

Teleomorph vs Anamorph
The teleomorph
(perfect stage) is the
sexual stage
Nectria - perithecia
The anamorph
(imperfect stage) is
the asexual stage
Fusarium - conidia
** Images and lecture material were not entirely created by J. Bond.
Some of this material was created by others.**
How pathogens attack plants
Southern leaf rust of corn
Apple scab
Remember: most microbes are not pathogens on most plants!
Infection Process
Pathogens must gain access into plants to cause
disease
• Viruses – Wounds
• Bacteria – Wounds, natural openings
• Fungi and Fungal Like Organisms – Wounds,
natural openings, and direct penetration
• Nematodes – direct penetration
Pathogens use plants for
food, but most of the
“food” is inside the cell.
To get to this food,
pathogens must first
penetrate the cell wall.
To penetrate the cell wall,
pathogens must first get
past the plant cuticle
(usually).
Regular cell wall
•2 layers: cellulose, pectin,
hemicelluloses, lignin
Epidermal cell wall
•2 layers plus cutin and wax
covering.
•Tough to get through
•VERY tough to get through
Mechanical force
• Only fungi, nematodes, and
parasitic plants use mechanical
force to get into the cell
• Most use force to get through
wax layer (although they must
adhere to the wax during
penetration)
• Adherence is usually by
appressoria
Appressoria can exert tremendous pressure!
•Melanin strengthens fungal cell wall in
appressoria and appears to be an important
pathogenicity factor
•Appressoria also secrete cutinases, cellulases,
pectinases
- Once past the cuticle,
fungus must continue to
secrete cellulases,
pectinases,
proteinases to enter each
and every cell.
Utilization of the protoplast
• The protoplast contains the “food” that most
pathogens are after
• But this food must first be degraded, then absorbed
• Degradation by enzymes - amylases, lipases,
phospholipases, proteinases