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Doctors Medicines MCQs Q&A

Which pathogen causes small yellowish round to oval spots on the leaves of maize and that spots gradually increase in area into bigger elliptical spots?

Which pathogen causes small yellowish round to oval spots on the leaves of maize and that spots gradually increase in area into bigger elliptical spots? Correct Answer Conidiophores

The correct answer is ​Conidiophores.

Key Points

  • Leaf blight, (Helminthosporium maydis) is a fungal disease of maize.
  1. Symptoms:
  • ​The fungus affects the crop at a young stage. Small yellowish round to oval spots is seen on the leaves.
  • The spots gradually increase in the area into bigger elliptical spots and are straw to grayish brown in the center with dark brown margins.
  • The spots coalesce giving a blighted appearance.
  • The surface is covered with olive green velvety masses of conidia and conidiophores.
  1. ​Pathogen:
  • ​Conidiophores are in a group, geniculate, mid-dark brown, pale near the apex, and smooth. 
  • Conidia are distinctly curved, fusiform, pale to mid-dark golden brown with 5-11 septa.
  • The optimum temperature for the germination of conidia is 8 to 27˚C.

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