Inheritance of a Minute Uredinium Infection Type of Bean Rust in Bean Breeding Line 814

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Abstract
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 .times. ''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 .times. ''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 .times. 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 .times. US#3 agreed with the F2 segreagtions. The gene conditioning the minute uredinium infection type in 814 apparently is epistatic to the gene conditioning the necrotic fleck in US#3.