Effects of Corn Plant Age and Cultivar on Resistance to Cercospora zeae-maydis and Sensitivity to Cercosporin

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Abstract
Three cultivars of corn with different degrees of resistance to Cercospora zeae-maydis were grown in the greenhouse. Leaf disks from 1-, 2-, and 3-mo-old plants were either treated with 1.2 .mu.M cercosporin or inoculated with a mycelial suspension of C. zeae-maydis. Cerosporin treatment caused significantly less ion leakage from disks of older plants. Significantly more stomates of older plant tissue were penetrated by the fungus. No varietal difference was detected for either sensitivity to cercosporin or susceptibility to C. zeae-maydis. The data indicate that a real age-dependent resistance to C. zeae-maydis exists in corn and suggest that the mechanism of this resistance is different from the varietal resistance seen in the field.