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Mutations Affecting Virulence in Puccinia recondita. G. Statler, Professor, Department of Plant Pathology, North Dakota State University, Fargo 58105; Phytopathology 75:565-567. Accepted for publication 4 December 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-565.

Wheat (Triticum aestivum) leaves inoculated with Puccinia recondita were treated with a chemical mutagen N-methyl-N'-nitro-N-nitrosoguanidine (NTG) in an attempt to alter virulence. Leaves were incubated for 10- 12 days in NTG. Subsequently, uredospores were collected and inoculated onto near-isogenic “tester” wheats on which culture X65 of P. recondita was avirulent. Isolations were made from pustules showing a virulent infection type, increased, and evaluated on near-isogenic lines. Nine cultures with mutations to virulence were developed by NTG treatment. Genes in P. recondita for virulence and avirulence on wheat have been designated p and P, respectively, and assigned a number corresponding to that of the Lr gene for resistance in the host. Mutations to virulence were induced at the p1, p3, p16, p17, p27, and p29 loci. Seven cultures with mutations to avirulence were recovered by evaluating mutations to virulence on a full set of near-isogenic lines. Mutations to avirulence were recovered at the P2a, P2c, P23, and P28 loci. Seven mutations to orange color were detected by treating the red-orange parent with NTG.