Author
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Stavely, J |
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Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/7/1999 Publication Date: N/A Citation: 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, common bean, is economically and environmentally preferable. The great pathogenic variabilty of the rust pathogen makes resistance that will remain effective over distance and time hard to achieve. In 1998 bean rust epidemics were only light except in a few scattered locations. Results are summarized from multi-location, field evaluations of relative resistance/susceptibility of 25 snap and 38 dry bean breeding lines or new cultivars from nine public and four private bean breeders. The nine snap bean and 19 dry bean entries in these nurseries that were resistant at all field locations were later evaluated in the greenhouse at Beltsville, resulting in determination that eight of the snap bean, but only four of the dry bean entries are resistant to all 90 races of the rust fungus now maintained at Beltsville. However, 11 more of the dry bean entries are homozygous for the Ur-3 gene that still remains effective in field control of rust in the united States, but Ur-3 does not control 46 of the 90 races maintained at Beltsville. The Ur-11 with Ur-3, Ur-4, or other genes from lines released from Beltsville are being incorporated into many dry bean breeding programs to give resistance to all 90 races. Rust resistance in beans will improve production efficiency, reduce losses, and reduce fungicide usage by farmers to improve efficiency and stability of food supply for consumers. Technical Abstract: Losses from bean rust, caused by Uromyces appendiculatus, were generally light with a few scattered, more severe incidences in 1998. Among 25 snap bean entries and 38 dry bean entries that were tested in three snap bean and four dry bean production areas and Beltsville, nine snap bean and 19 dry bean entries were resistant at all locations. Greenhouse testing with multiple pathogenic races of the rust fungus indicated that eight of these snap bean entries, but only four of the dry bean entries are resistant to all 90 available races. In addition, 11 other of the dry bean entries are homozygous for the Ur-3 gene that is effective in all field locations and throughout the dry bean production area of continental United States. However, 46 of the 90 races now identified and maintained at Beltsvile are not controlled by Ur-3. Beltsville germplasm lines under development with three such genes are being used by breeders to develop new cultivars resistant to all identified races of the rust fungus. |
