Evaluation of resistance of selected corn lines to common smut, ustilago maydis (dc.) Corda

In order to evaluate selected corn lines to common smut (Ustilago maydis), an experiment was conducted in a complete randomized block design, with 30 treatments (lines) in four replications, in Kabutar Abad Experimental Station. For artificial inoculation, fungal inoculum consisting of a mixture of sporidia was applied to ears, 2 to 3 days after silk stage after removing the cobs with pruning shears by injection of 3 ml of inoculum (106 spore/m!) into the cut cobs. At harvesting time, the disease incidence (D.I.), based on infection rate in each line, and disease severity (D.s), based on disease progress in each ear, were evaluated. The results showed that by the cut cob injection method, high percentages of infected ears were obtained (more than 90%). Based on disease severity (scale 0-7) on ears, lines were grouped in four categories consisted of three lines without infection (Immune), two lines with high tolerance, 15 lines moderately resistant to moderately susceptible and 10 lines susceptible or highly susceptible.