Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 30, 2011
Publication Date: March 3, 2011
Citation: Mcintosh, R.A., Zhang, P., Cowger, C., Parks, W.R., Lagudah, E.S., Hoxha, S. 2011. Rye-derived powdery mildew resistance gene Pm8 in wheat is suppressed by the Pm3 locus. Theoretical and Applied Genetics. 123:359-367. Interpretive Summary: When disease resistance genes from wild wheat relatives are introduced into the genome of cultivated wheat, the genes sometimes have reduced or no effect in their new background. It was discovered that the resistance to powdery mildew, conferred by the gene Pm8, was suppressed in some wheat cultivars. A gene linked to the suppressive effect was identified near two storage protein genes, Gli-A1 and Glu-A3. These genes are in turn closely linked to another powdery mildew resistance gene, Pm3. The suppression of Pm8 is predicted to involve the products of the Pm3 locus.
Technical Abstract: Genetic suppression of disease resistance is occasionally observed in hexaploid wheat or in its interspecific crosses. The phenotypic effects of genes moved to wheat from relatives with lower ploidy are often smaller than in the original sources, suggesting the presence of modifiers or partial inhibitors in wheat, especially dilution effects caused by possible variation at orthologous loci. However, there is little current understanding of the underlying genetics of suppression. The discovery of suppression in some wheat genotypes of the cereal rye chromosome 1RS-derived gene Pm8 for powdery mildew resistance offered an opportunity for analysis. A single gene for suppression was identified at or near the closely linked storage protein genes Gli-A1 and Glu-A3, which are also closely associated with the Pm3 locus on chromosome 1AS. The Pm3 locus is a complex of expressed alleles and pseudogenes embedded among Glu-A3 repeats. In the current report, we explain why earlier work indicated that the mildew suppressor was closely associated with specific Gli-A1 and Glu-A3 alleles, and predict that suppression of Pm8 involves translated gene products from the Pm3 locus.