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Punch Inoculation for Measuring Resistance of Corn Leaf Tissue to Helminthosporium maydis. M. Matsuyama and Saul Rich, The Connecticut Agricultural Experiment Station, New Haven, 06504. Phytopathology 64:429-430.

The punch-inoculation method was used to inoculate corn seedlings with Helminthosporium maydis Nisik. & Miyake.  Spots are crushed on corn leaves with a punch just hard enough to injure the tissue without punching out a hole.  A spore suspension is brushed on the crushed spot and the inoculated plants are incubated in plastic bags for 24 hr.  This technique can be used to measure accurately the relative resistance of leaf tissue of various corn lines to southern corn leaf blight within 48 hr after inoculation.  The method can also be used to measure the relative resistance of tissues from leaves of different ages.