Breeding wheat for resistance to physiologic forms of stem rust
1927
Aamodt, O.S.
1. Crop improvement which is concerned with disease resistance must take into consideration: (a) The possible existence of physiologic forms of the pathogenic organism, (b) the need of a survey to determine the prevalence and distribution of the various forms, (c) the varietal reactions of the host to particular forms, (d) the reactions between host and parasite as definite genetic characters, and (e) the possibility of combining the resistance to all forms within a single desirable commercial variety. 2. Studies of species crosses have demonstrated that resistance to stem rust can be transferred from the durums and emmers to common wheats. 3. A greenhouse test is necessary to determine the mode of inheritance of the reaction of a variety or hybrid to particular physiologic forms. A field test is necessary in order more fully and accurately to determine varietal reaction to rust under the particular environmental conditions where the variety is to be grown. 4. Genetic evidence has been obtained regarding the mode of inheritance of resistance in wheat to many physiologic forms of stem rust. This evidence, as well as that from extensive breeding studies conducted under field conditions, substantiates the belief that it is entirely possible to produce a bread wheat resistant to all of the known physiologic forms of stern rust. Some varieties with fairly high rust resistance and of good milling quality are already available. Better and more highly rust-resistant varieties probably can be obtained eventually.
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