Large-scale Maize Seedling Infection with Exserohilum turcicum in the Greenhouse.

Northern corn leaf blight (NCLB) is a serious foliar disease of maize (Zea mays) worldwide and breeding for resistance is of primary importance for maize crop protection. Phenotyping for NCLB resistance is well established in the field, but such experiments depend on suitable environmental conditions and are seasonal. Here we describe a greenhouse seedling approach that is suitable for testing thousands of seedling plants in a single experiment with a duration of 37 days. Three scoring methods were used to quantify the disease severity: the area under the disease progress curve (AUDPC), the primary diseased leaf area of the inoculated leaves at 16 days post inoculation (PrimDLA at 16 dpi) and the incubation period (IP) that was determined as days from inoculation to symptom appearance. By testing a diverse panel of maize genotypes, a high correlation between the three different methods was observed (81.9% to 94.1%), indicating that each of scoring methods can be applied for disease quantification. Thus, the seedling assay developed served as a relatively simple and high-throughput method for phenotyping NCLB disease resistance under greenhouse condition.