Lecture 2 General Principles & Gram + Bacteria

4 Pages

Plant Biology
Course Code
PBIO 117
Terrence P.Delaney

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8/29/13 General Principles of Plant Pathology  Stages of disease cycle Infection Host recognition Invasion Colonization Penetration Growth and/or Attachment reproduction of pathogen Incubation Dissemination of pathogen Symptom Development Dissemination of (secondary inoculum) Production of Primary inoculum Primary inoculum Overwintering stage Dormant period  Types of Penetration by fungi o Direct o Through natural openings (ie. Stomata) o Natural wounds  Penetration by bacteria o Through stomata (water needed) o Through wound o Hydrathode o Nectarthode  Bacteria as a plant pathogen o Can cause  Spots/flecks  Mosaic patterns/ pustules  Distortion of leaves/shoots  Crown gall  Plant death  Plant Pathogenic Bacterial o Can be grouped based on cell wall structure  Gram positive – retain crystal violet stain  Thick layer of peptidoglycan in cell wall  Gram negative- does not retain CV stain  Thinner layer of peptidoglycan (possibly why stain rinses out so easily)  Taxonomy o … genus speciessubspecies pathovar  Gram Positive Genera (bacteria) o Clavibacter-  Symptoms  wilting  marginal necrotic leaf lesions  cankers  bird’s eye lesion (raised necrotic spots surrounded by white halo)  Stem infection (inner material is reddish brown, necrotic material can fill pith and cause cankers)  Cycle of infection  Management  Plant “certified” seeds, never use seeds from an infected plant  Clean soil/crop rotation  R
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