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Response of Detached Apple Leaves to Venturia inaequalis. R. L. Nicholson, Department of Botany and Plant Pathology and Biochemistry, Purdue University, Lafayette, Indiana 47907; S. Van Scoyoc(2), J. Kuc(3), and E. B. Williams(4). (2)(3)(4)Departments of Botany and Plant Pathology and Biochemistry, Purdue University, Lafayette, Indiana 47907. Phytopathology 63:649-650. Accepted for publication 20 November 1972. DOI: 10.1094/Phyto-63-649.

Hypersensitive, resistant, and susceptible symptoms of scab infection were expressed at the same time and in the same manner on detached as on attached apple leaves. Symptoms were confined within the borders of inoculation sites except in susceptible interactions where extensive stromatic growth of the fungus occurred. The hypersensitive response was characterized by the complete collapse and necrosis of inoculation sites within 2 to 10 hr after the initial hypersensitive pit response.