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Adult Plant Rust Resistance Associated with Leaf Pubescence in Common Bean. Margaret T. Mmbaga, Department of Plant Pathology, University of Nebraska, Lincoln 68583-0722. James R. Steadman, Department of Plant Pathology, University of Nebraska, Lincoln 68583-0722. Plant Dis. 76:1230-1236. Accepted for publication 1 August 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-1230.

Rust disease reactions among pubescent and glabrous genotypes of Phaseolus vulgaris from diverse genetic origins were compared at seedling and adult plant stages in the glasshouse and field. The primary leaves of all pubescent genotypes were moderately susceptible or moderately resistant to two single uredinium cultures of Uromyces appendiculatus inoculated individually or as a mixture. Size and, in a few cases, density of uredinia were reduced significantly on the upper trifoliolate leaves to give moderately resistant or resistant reactions. Evaluation of reaction to 26 individual bean rust cultures of different virulence patterns showed race-nonspecific reduced uredinia size in the upper trifoliolate leaves of the pubescent genotypes and in one glabrous genotype. Selection against bean rust susceptibility at the seedling stage could result in the loss of useful germ plasm that expresses resistance at the adult plant stage.