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Ecology and Epidemiology

Nonspecific Resistance to Rust in Pubescent and Glabrous Common Bean Genotypes. Margaret T. Mmbaga, Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln 68583-0722; James R. Steadman, Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln 68583-0722. Phytopathology 82:1283-1287. Accepted for publication 26 May 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-1283.

Six pubescent and three glabrous bean genotypes from diverse genetic and geographic origins were inoculated on the primary leaves with uniform amounts of urediniospores. Air turbulence was created in small chambers on each genotype, and amounts of spore production were measured by the secondary infection they produced on the trifoliolate leaves and by counts of infective spore units. The sporulating capacity of the primary and trifoliolate leaves was measured on each genotype. Seven bean genotypes, six of which were pubsescent, showed a moderately susceptible reaction to rust on the primary leaves and reduced uredinia size and density on the upper leaves. Rust on the same bean genotypes had low sporulating capacity on the primary and trifoliolate leaves. These resistance components reduce disease progress and would need to be selected for in the field. Although abaxial long leaf trichomes are associated with nonspecific resistance to bean rust, they are not the only factor involved.