Present address: CIRAD, UMR DAP, TA A-96/03, Avenue Agropolis, 34398 Montpellier Cedex 5, France.
Independent evolution of functional Pm3 resistance genes in wild tetraploid wheat and domesticated bread wheat
Article first published online: 9 DEC 2008
© 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd
The Plant Journal
Volume 57, Issue 5, pages 846–856, March 2009
How to Cite
Yahiaoui, N., Kaur, N. and Keller, B. (2009), Independent evolution of functional Pm3 resistance genes in wild tetraploid wheat and domesticated bread wheat. The Plant Journal, 57: 846–856. doi: 10.1111/j.1365-313X.2008.03731.x
- Issue published online: 19 FEB 2009
- Article first published online: 9 DEC 2008
- Received 27 August 2008; revised 9 October 2008; accepted 16 October 2008; published online 9 December 2008.
- genetic diversity;
- disease resistance;
- wild wheat;
- powdery mildew
The Pm3 alleles of cultivated bread wheat confer gene for gene resistance to the powdery mildew fungus. They represent a particular case of plant disease resistance gene evolution, because of their recent origin and possible evolution after the formation of hexaploid wheat. The Pm3 locus is conserved in tetraploid wheat, thereby allowing the comparative evolutionary study of the same resistance locus in a domesticated species and in one of its wild ancestors. We have identified 61 Pm3 allelic sequences from wild and domesticated tetraploid wheat subspecies. The Pm3 sequences corresponded to 24 different haplotypes. They showed low sequence diversity, differing by only a few polymorphic sequence blocks that were further reshuffled between alleles by gene conversion and recombination. Polymorphic sequence blocks are different from the blocks found in functional Pm3 alleles of hexaploid wheat, indicating an independent evolution of the Pm3 loci in the two species. A new functional gene was identified in a wild wheat accession from Syria. This gene, Pm3k, conferred intermediate race-specific resistance to powdery mildew, and consists of a mosaic of gene segments derived from non-functional alleles. This demonstrates that Pm3-based resistance is not very frequent in wild tetraploid wheat, and that the evolution of functional resistance genes occurred independently in wild tetraploid and bread wheat. The Pm3 sequence variability and geographic distribution indicated that diversity was higher in wild emmer wheat from the Levant area, compared with the accessions from Turkey. Further screens for Pm3 functional genes in wild wheat should therefore focus on accessions from the Levant region.