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Introgression of Powdery Mildew Resistance from Rye into Wheat. M. Heun, Institute of Agronomy and Plant Breeding, 0-8050 Freising-Weihenstephan, Federal Republic of Germany; B. Friebe, Institute of Agronomy and Plant Breeding, 0-8050 Freising-Weihenstephan, Federal Republic of Germany. Phytopathology 80:242-245. Accepted for publication 30 August 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-242.

A recently developed set of isogenic wheat-rye addition, substitution, and translocation lines has been analyzed for its potential to offer new sources of powdery mildew resistance originating from rye. These lines were compared with a set of cultivars/lines carrying the resistance genes Pm1 to 9 and Mlk. 4 and 6 Thatcher wheat reacted highly susceptible to wheat powdery mildew, whereas the triticale line derived from 4 Thatcher and Prolific rye showed a high level of resistance. The rye chromosomes 1R, 4R, and 7R do not condition any powdery mildew resistance against the isolates used here. The powdery mildew resistance of the 2D/2R substitution line was highly effective, whereas Pm7, assumed to originate from 2R, gave mainly susceptible reactions. Cytological analyses, done by using the Giemsa C-banding technique for chromosome identification, of Transec wheat carrying Pm7 imply that the "Transec" translocation consists of a complete short arm of chromosome 4B of wheat and about half of the proximal region of the long arm of that chromosome and a rye segment derived from the distal part of the long arm of chromosome 5R of rye. The chromosome 2R of the 2D/2R substitution line showed the typical C-banding pattern after differentially staining the constitutive heterochromatin. The rye chromosome 6R conditioned absolute resistance to all powdery mildew isolates tested and is shown to be located at the long arm of that chromosome. For this resistance, we propose the temporary gene symbol M/P6L. In addition, we present a way of transferring this resistance gene using a 6BS/6RL wheat-rye translocation line.

Additional keywords: gene identification.