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Resistance

Low Infection Types Produced by Puccinia graminis f. sp. tritici and Wheat Lines with Designated Genes for Resistance. A. P. Roelfs, Research plant pathologist, Cereal Rust Laboratory, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, University of Minnesota, St. Paul, 55108; D. V. McVey, research plant pathologist, Cereal Rust Laboratory, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, University of Minnesota, St. Paul, 55108. Phytopathology 69:722-730. Accepted for publication 2 February 1979. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1979. DOI: 10.1094/Phyto-69-722.

Between 72 and 120 wheat lines were tested annually from 1970 through 1977, to characterize the reactions of various specific resistances to stem rust caused by 100 to 300 cultures of Puccinia graminis f. sp. tritici that represented the ranges of pathogen virulence detected in the annual race survey. Annually, 10 to 100 cultures also were retested. The wheat genotypes that were studied can be classified in three groups based on responses to North American rust fungus cultures: (i) those susceptible to all or nearly all of the cultures studied, ie, Sr9f, 9g, 16, 18, 19, 20, 28, LC, McN, and Kt’2’; (ii) those differential in response, ie, Sr5, 6, 7a, 7b, 8, 9a, 9b, 9d, 9e, 10, 11, 12, 14, 15, 17, 21, 23, Tt-1, Tt-3, Tmp, dp-2, and X; and (iii) those “universally” resistant or nearly so, ie, Sr13, 22, 24, 25, 26, 27, 29, 30, Tt-2, and Gt. Although the low infection types produced by a range of avirulent cultures on a host with the corresponding gene for resistance over a range of environmental conditions generally were similar, numerous exceptions were observed.