Introduction to phytopathology concepts, components and causes

Bsc and MSc Botany study material

1. Introduction to phytopathology-concepts, components and causes course name- m.sc special paper ( mycology and plant pathology) Dr. Vishnupriya Sharma

2. PHYTOPATHOLOGY Phytopathology is also known as plant pathology Pathology is a term made up of two gr. Words pathos= suffering; logos= to study or discourse, thus plant pathology is the study of suffering or diseases of plants

3. objectives Etiology - causal organism, living or non living entity responsible for causing diseases in plants Pathogenesis - disease development or host pathogen interaction Epidemiology - also called as epiphytotics in case of plant diseases. It is a wider term and includes plant, pathogen, environment, carryover of pathogen to the next season and again spread and dispersal of disease Control –devising suitable methods to control, reduce or minimise the losses due to pathogen

4. Concept of disease According to Stakman and Harrar a disease can be defined as a physiological disorder or structural abnormality that is deleterious to the plant or any of its parts or products that reduces their economic value Disease is any departure from normal health It is a malfunctioning or pathological process resulting in suffering

5. Components of disease 3 components Susceptible host, virulent & aggressive pathogen , favourable environment These 3 components constitute the disease triangle FOURTH FACTOR-TIME-an important factor of plant disease.

6. Causes of diseases 1. animate or living caused by bacteria, fungi, algae, nematodes, insects, virus and mycoplasmas 2. inanimate or non-living due to nutrition deficiency, deficiency in nutrient contents of soil, excessive use of insecticide or plant protecting chemicals

7. Classification of diseases

8. On the basis of extent to which disease are associated with plant 1. Localised disease- limited to a definite area 2. Systemic disease- spreads through the entire plant

9. On the basis of mode of primary infection

10. According to the type of host plant

11. Symptoms can be broadly divided into 3 categories

12. necrosis Leaf spot Streaks or stripes Blights Damping off Scald/scorch/burn Rots Wilting Die-back Cankers Chlorosis Blotch Scab Pustules/white blisters Smuts Rusts mildews

13. Hypertrophy-abnormal increase in the size of organ Elongated internodes Galls and tumors Witches broom Curls Floral abnormalities

14. Hyperplasia- abnormal increase in number of cells due to cell division Chlorosis Reduction of individual organ Floral abnormalities

15. Control of plant diseases Methods of plant disease control are generally classified on the basis of nature of agent employed to control the disease:-

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