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Components of Partial Resistance to Blue Mold in Six Tobacco Genotypes Under Controlled Environmental Conditions. Rebeca C. Rufty, Departments of Crop Science and Plant Pathology, North Carolina State University, Raleigh 27695; C. E. Main, Departments of Crop Science and Plant Pathology, North Carolina State University, Raleigh 27695. Phytopathology 79:606-609. Accepted for publication 19 January 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-606.

Two susceptible and four partially resistant tobacco genotypes were evaluated for components of partial resistance to blue mold. Disease efficiency, incubation period, latent period, degree of colonization, and sporulation capacity were measured under high and low inoculation density in experiments conducted at the Southeastern Plant Environmental Laboratory (North Carolina State University Phytotron), Raleigh, NC. Genotypes differed significantly for all components of resistance in all trials. Commercial cultivars Speight G-70 and McNair 944 were consistently the most susceptible genotypes based on all components of partial resistance measured. Partially resistant genotypes Chemical Mutant, NC-BMR 42, and NC-BMR 90 produced fewer and smaller lesions, had lower sporulation capacity, and exhibited longer patent periods than susceptible genotypes. Breeding line NC-BMR 90 was superior to all other partially resistant genotypes in this study. The presence of multiple resistance components in NC-BMR 90 makes this line a desirable source of blue mold resistance. Results obtained in these experiments corroborated field observations and indicate that deployment of tobacco germ plasm with partial resistance to blue mold should reduce onset and progress of blue mold epidemics.

Additional keywords: Nicotiana tabacum, Peronospora tabacina.