This document summarizes the key principles of plant infection: 1) Penetration is the entry of the pathogen into the host, which can occur directly through the plant surface, through wounds, or through natural openings like stomata, hydathodes, or lenticels. 2) Infection is the establishment of the pathogen within the host plant by procuring nutrients from host cells or tissues. 3) Invasion is the spread of the pathogen within the host, which can be intercellular or intracellular depending on the type of pathogen. 4) Dissemination refers to the spread of the pathogen from one plant to another, which can occur autonomously through soil, seeds, or plant parts,

1. PRINCIPLES OF PLANT INFECTION
DR. RAJBIR SINGH
Assistant Professor
Department of Plant Pathology
Gochar Mahavidyalaya, Rampur Maniharan, Saharanpur (UP), India
Affiliated to Ch. Charan Singh University, Meerut (UP), India
Email: rajbir25805@yahoo.com, rajbirsingh2810@gmail.com
Cell No. 91-9456613374

2. (A). Penetration - “Entry of pathogen in
the host is called penetration”
(i). Direct penetration
fungi, nematodes & parasitic pls.
Mechanic forces & enzymatic softening
By appressorium in fungi

3. 3. Haustorium

4. 2. Appresorium

6. (ii). Through wounds
All bacteria, most fungi, some virus & viroid
Enter through wounds
Virus, MLO, RLO enter through wounds made
by vector
iii). Through natural opening
(a). Stomata
Many fungi & bacteria enter through stomata

7. Penetration through Stomata

8. (b). Hydathodes
are more or less permanently open pores at
the end on the tip of leaves
Bacteria enter through hydathodes

10. (c). Lenticels
Are openings on fruits, stem, tubers that
are filled with loosely connected cells to
allow passage of air
Few fungi and bacteria enter through lenticels

11. (B). Infection
“The establishment of a pathogen with in a host
plant”
“Infection is the process by which pathogen
establish contact with susceptible cell or
tissues of the host and procure nutrients
from them”

12. (C). Invasion
“ The spread of the pathogen with in the host”
Fungi spread - Intercellular, intercellular
Bacteria - Intercellular, intercellular
Virus, virods, MLO, phytoplasma & RLO
By moving from cell to cell interacellularly

13. (D). Dissemination or Dispersal of
Pathogen
(A). Autonomous Dissemination
(1). By Soil
(2). By Seeds
(3). By Plant and Plant Parts

14. (B). Passive Dissemination
(1). By Air
(2). By Water
(3). By Vectors
(4). By Humans

15. Thank You