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Inheritance of a Minute Uredinium Infection Type of Bean Rust in Bean Breeding Line 814. J. A. Kolmer, Former graduate research assistant, Department of Plant Pathology, University of Minnesota St. Paul 55108, Present address: Department of Plant Pathology, North Carolina State University, Raleigh 27650; J. V. Groth, associate professor, Department of Plant Pathology, University of Minnesota St. Paul 55108. Phytopathology 74:205-207. Accepted for publication 26 August 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-205.

Uromyces appendiculatus isolate S1-5 produces an infection type characterized by a minute uredinium on bean line 814. Cultivars Early Gallatin and Pinto 111 are moderately and fully susceptible, respectively, to S1-5, S1-5 produced the minute uredinium on the F1 of 814 Pinto 111. The F2 segregated in a 3:1 ratio for minute- :large-uredinia infection types. Early Gallatin has a single dominant gene conditioning hypersensitive resistance to U. appendiculatus isolate P10-1. The F1 from 814 Early Gallatin were resistant to both S1-5 and P10-1. The F2 segregated in a 9:3:3:1 ratio for resistance to isolates P10-1 and S1-5: resistance only to P10-1: resistance only to S1-5: susceptibility to both isolates. Bean cultivar US#3 has a single dominant gene conditioning a large, sometimes sporulating fleck, when inoculated with S1-5. F1 progeny of 814 US#3 produced minute necrotic flecks when inoculated with S1-5. The F2 segregated in a 12:3:1 ratio: progeny with minute, non-necrotic uredinia grading into minute necrotic flecks: sporulating uredinia surrounded by large areas of necrosis: and large non-necrotic uredinia, respectively. Segregations in the F3 families of 814 US#3 agreed with the F2 segregations. The gene conditioning the minute uredinium infection type in 814 appears to be epistatic to the gene conditioning the necrotic fleck in US#3.

Additional keywords: Phaseolus vulgaris, specific resistance.