1Department of Disease and Stress Biology, John Innes Centre, Colney Lane, Norwich Research Park, Norwich, NR4 7UH, U.K.; 2Monsanto UK Ltd., The Maris Centre, Hauxton Road, Trumpington, Cambridge, CB2 2LQ, U.K.
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Accepted 8 June 2004.
Two mutants were isolated in wheat that showed enhanced resistance towards Puccinia striiformis f. sp. tritici, the fungal causal agent of yellow rust. The altered phenotype of I3-48 is due to a minimum of two mutation events, each showing a partial, additive effect, with one mutation segregating with a deletion on the long arm of chromosome 4D. In the case of I3-54, the enhanced resistance is due to a single, dominant mutation. In both mutants, the expression of the enhanced resistance is growth-stage specific. With I3-54, the full resistance phenotype is apparent from the third seedling leaf onwards, while with I3-48, a full resistance phenotype is only seen on the tenth and subsequent leaves. In addition to the enhanced resistance towards yellow rust, I3-48 also shows enhanced resistance towards brown rust, and I3-54 shows enhanced resistance to powdery mildew.
© 2004 The American Phytopathological Society