Development of a Method to Evaluate Tobacco Genotypes for Resistance to Angular Leaf Spot in the Greenhouse

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Abstract
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 disese 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.