Multigenic Inheritance of Stem Rust Resistance in Wheat1
- D. R. Knott2
Eight cultivars or lines of common wheat (Triticum aestivum L.) that were thought to have adult plant or field resistance to stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. and E. Henn.) were selected—‘Hope’, ‘Hopps’, ‘Marquillo’, ‘Thatcher’, ‘Bonza’, ‘Chris’, Minnesota 11-50- 17 and MRFY. The eight were crossed to produce four double crosses with the objective of combining genes for field resistance. A breeding procedure was used that resulted in the elimination of specific seedling resistance to race 15B-1 of stem rust, and the selection of lines having field resistance to 15B-1. During several years of testing, the selected, resistant lines proved to have resistance to mixtures of the prevalent and most virulent races of stem rust in North America. Twenty lines were tested in the 1976 International Spring Wheat Rust Nursery. All 20 were resistant at every North American location, and three had some resistance at all locations. Thus, 17 of the 20 lines appeared to have some type of specific resistance, while three had resistance against a broader range of races.
The inheritance of rust resistance was studied in crosses between 61 of the selected lines and a susceptible parent. The results showed that in most crosses resistance was recessive and involved several genes that have small, probably cumulative effects, and act only in adult plants. In one line there was an indication that one major gene was involved. The resistance is clearly different than that controlled by the named Sr genes for specific resistance. However, there is no reason to think that it is general resistance, although its genetic complexity may make it more durable than resistance based on major genes for specific resistance.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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