Different plants pathogen tjckcig, Study notes of Plant pathology

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Fundamentals of Plant Pathology

BAG

Classification of diseases

Ankur Mukhopadhyay

M.Sc., PhD

Assistant Professor, Dept. of Agriculture

Brainware University, Barasat

1. Mode of perpetuation and primary infection.
2. Infectious nature.
3. Production and spread of the inoculums or

number of pathogen generations.

1. Extents of plant parts affected.
2. Causes of the disease.
3. Occurrence and geographic distribution.

7. Plant part affected.

1. Crop plants affected.

9. Symptoms produced on host plants.

criteria:

Soil borne diseases

• (^) The pathogen survive in the soil or on the

infected plant debris lying in the soil

either as their resting spore or as mycelia

strand.

• (^) They all attack the root system of host plants.
• (^) E.g Damping off (Pythium sp.), seedling

blight [phytophthora,

Fusarium sp.\

Air borne

diseases

• Some pathogen infect the host plant

through

air and bring primary and secondary

infection.

• E.g. Rusts, powdery mildews

Seed borne diseases

• Some pathogen survive as dormant

mycelium or other propagative

structures in the seeds of host plants.

• E.g. Loose smut of wheat (internally

On the basis of production and spread of the inoculum or number of pathogen generation

1. Single cycle or monocyclic disease:

• (^) The increase of disease is mathematically analogous to simple interest money.
• (^) Those disease which have only generation in one cropping

season.

• (^) E.g. loose smut of wheat

On the basis of production and spread of the inoculum or number of pathogen generation

1. Multiple cyclic or polycyclic disease:

• (^) The increase in disease is mathematically analogous to compound interest of money.
• (^) Those disease which have more than Dne generation in a

chopping season.

• (^) E.g. late blight of potato

Three types of diseases on the basis of the cause

1. Biotic disease Fungal disease, bacterial disease, phytoplasma disease,

phanerogamic disease, nematode

disease.

1. Mesobiotic disease

Disease caused by virus or viroid.

1. Abiotic disease By abnormal environmental condition

On the basis of occurrence and geographic dis tribution

1. Epidemic disease:

• (^) A disease usually occurs widely but periodically in a destructive form is reffered as epidemic or epiphytotic disease.
• (^) e.g. late blight of potato — Irish famine

On the basis of occurrence and geographic dis tribution

1. Sporodic disease

• (^) Occur at very irregular intervals and locations and in relativity fewer instances.
• (^) e.g. udbatta disease of rice, angular leaf spot of cocumber

On the basis of occurrence and geographic distribution

1. Pandemic disease

• (^) An epidemic occuring worldwide, or over a very wide area, crossing international boundaries and usually affecing a large number of population.
• (^) e.g. Wheat rust Ucta

1. Downy

• mildew (^) Symptoms appears as yellow to white patches on the lower surface of leaves.
• (^) This disease is caused by family peronosporaceae (Fungus).
• (^) e.g. DMO of grapevine