Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/1997
Publication Date: N/A
Interpretive Summary: Epidemics in crops of edible snap and dry beans caused by the bean rust fungus, result in serious losses in production, losses to farmers, market instability, and consumer price increases. A few fungicides control rust, but resistance in the host is economically and environmentally preferable. The great variability of the rust pathogen makes resistance that will remain effective over distance and time hard to achieve. Locations and severity of 1996 United States bean rust epidemics are reported. Results are summarized from multi-location, field evaluations of relative resistance/susceptibility of 95 snap and 24 dry bean breeding lines from five private and four public breeders. Later greenhouse evaluations indicated that 11 of the 25 snap bean lines and one line and one cultivar of the nine dry bean entries that were resistant at all field locations are resistant to all 87 available races, and derive their resistance from Beltsville-released germplasm. Newly identified races of the rust fungus at Beltsville in 1996, included one from Honduras and two from Egypt. The Honduran race is the first discovered that produces susceptible rust reactions on many plant introductions previously resistant to all available races, but most Beltsville releases are resistant to this race and all others. Rust resistance in beans will improve production efficiency, market stability, food supply dependability, and reduction in fungicide use.
Technical Abstract: Losses from bean rust, caused by Uromyces appendiculatus, were most severe in North Dakota and Minnesota on dry beans, but less severe in other major dry bean production areas, and only light to moderate on snap beans in 1996. Among 95 snap bean lines and 24 dry bean lines or cultivars that were tested in three snap bean and four dry bean production areas and Beltsville, 25 snap bean lines and nine dry bean lines or cultivars were rust resistant at all locations where tested. Greenhouse testing with multiple pathogenic races of the rust fungus indicated that 11 of these snap bean lines, but only one dry bean line and one cultivar are resistant to all races. All of these lines that are resistant to all races of the pathogen are a Beltsville release or are derived from Beltsville releases. Among three newly identified races of the rust fungus is one obtained from Honduras that produces a susceptible rust reaction on most of the plant introductions that had been resistant to all previously identified races. However, most of the rust resistant germplasm releases from the Beltsville program are resistant to this and all other races.