Course Content
TERMS AND CONCEPTS USED IN PLANT PATHOLOGY
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CLASSIFICATION OF FUNGICIDES BASED ON CHEMICAL NATURE
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CLASSIFICATION OF FUNGICIDES BASED ON METHOD OF APPLICATION
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Learn introduction to plant pathology with Braimy – B.sc Agriculture
About Lesson

a) Inhibitors released by the plant in its environment:

  • Plants exude a variety of leaf and root exudates which contain amino acids, sugars, glycosides, organic acids, etc.
  • The inhibitory substances directly affect micro-organisms or encourage certain groups to dominate the environment which may act as antagonists to pathogen.
  • Eg : Tomato leaves secrete exudates which are inhibitory to Botrytis cinerea.
  • Red scales of red onion contain the phenolic compounds, protocatechuic acid and catechol, which diffuse out to the surface and inhibits the conidial germination of onion smudge fungus, Colletotrichum circinans.
  • Resistant varieties of apple secrete waxes on the leaf surface which prevents the germination of Podosphaera leucotricha (powdery mildew of apples).
  • Chlorogenic acid present in sweet potato, potato and carrot inhibits Ceratocystis fimbriata.

b) Inhibitors present in plant cells before infection:

  • Several phenolic compounds, in cells of young fruits, leaves or seeds are responsible for the resistance of young tissues to Botrytis.
  • Saponins have antifungal membranolytic activity which excludes fungal pathogens that lack saponinases. Ex: Tomatine in tomato and Avenacin in oats.
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