Evaluation location: Illinois, United States
2000 maize accessions were obtained from the 14,000 accessions in the NCRPIS collection in 1997. Accessions were selected by the maize curator (M. Millard) as representative of sweet and field corn germplasm from the U.S. and maize germplasm from other regions of the world adapted to temperate climates. Planting was on 22-May-1997 at the U. of Illinois South Farm, Urbana, Illinois. The trial included two replicates of single rows of approximately 15 plants per accession. Rows were spaced 0.76 m apart. Plant stands were adequate for all but 9 accessions. Plants at the 3 to 6-leaf stage were inoculated with E. stewartii on 25-JUN-1997 and 30-JUN-1997 in the first and second replicates respectively using the pinprick method. Inoculum was produced as described previously from a mixture of isolates including those collected in May 1997 from naturally infected plants in southern Illinois and those isolated from trials in Illinois in 1996 and maintained over winter in the greenhouse and at -80 degrees C. Reactions to E. stewartii were rated on a 1-9 scale where 1=no appreciable spread of symptoms from pinpricks; 2=limited spread with water-soaking, chlorosis, or necrosis within 3 cm of pinpricks; 3=limited spread from pinpricks with water-soaking, chlorosis, or necrosis predominantly toward tips of leaves; 4=abundant spread from pinpricks with water-soaking, chlorosis, or necrosis toward both ends of inoculated leaves, but no symptoms on noninoculated leaves; 5=minimal systemic infection observed as small, linear streaks of symptoms on noninoculated leaves; 6=moderate systemic infection with 5-25% symptomatic leaf area of noninoculated leaves and minimal stunting; 7=abundant systemic infection and stunting with 25-50% of the leaf area symptomatic; 8=severe systemic infection and stunting with 50-90% of the plant infected; and 9=90-100% infection, severe necrosis, or a dead plants. 0n 8-11 July and 16-17 ratings were performed. Checks 'Miracle'=1.9, 'Jubilee'=5.9.