Teleomorph vs Anamorph The teleomorph (perfect stage) is the sexual stage The anamorph (imperfect stage) is the asexual stage Nectria - perithecia Fusarium - conidia ** Images and lecture material were not entirely created by J. Bond. Some of this material was created by others.**

Remember: most microbes are not pathogens on most plants! How pathogens attack plants Apple scab Southern leaf rust of corn 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 Tough to get through Epidermal cell wall 2 layers plus cutin and wax covering. 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