Development of a Method to Evaluate Tobacco Genotypes for Resistance to Angular Leaf Spot in the Greenhouse. Mary J. Wannamaker, Graduate Research Assistant, Department of Crop Science, North Carolina State University, Raleigh 27695-7620. Rebeca C. Rufty, Assistant Professor, Departments of Crop Science and Plant Pathology, North Carolina State University, Raleigh 27695-7620. Plant Dis. 73:964-968. Accepted for publication 23 June 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0964.

A greenhouse technique was developed to evaluate tobacco genotypes for resistance to angular leaf spot. An artist’s airbrush was the most effective method of spraying inoculum uniformly on the abaxial surface of the two oldest leaves of plants at the four- to five-leaf stage. A suspension of Pseudomonas syringae pv. tabaci containing 10⁷ cfu/ml produced symptoms typical of those observed in the field. A preinoculation mist period of 0–18 hr did not increase the amount of disease. Postinoculation mist periods of 24, 36, and 48 hr significantly increased the amount of disease. A quantitative disease assessment scale was developed and used successfully to classify genotypes for disease resistance. Lesions observed in the greenhouse were similar in size, shape, and color to those observed in field plant beds. In addition, the rank order of genotypes in greenhouse and field plant beds was the same.