Haplotype diversity and evolutionary history of the Lr34 locus of wheat
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Leaf rust caused by Puccinia triticina is a major disease of wheat, and genetic resistance remains the best strategy for managing it. The resistance gene Lr34 has been key in the genetic management of wheat leaf rust worldwide. However, little is known about the geo-genetic diversity, history and origin of this unique gene. This study was conducted to provide a comprehensive analysis of the genetic diversity at the Lr34 locus of a world wheat germplasm collection. A total of 52 alleles were detected for the 10 Lr34 markers. On the basis of the Lr34-specific markers, the world collection was divided into five major haplotypes (H), of which H1 was consistently associated with the resistance phenotype Lr34+. Phenotypic data confirmed the susceptible phenotypes of H2, H3 and H4 and the susceptible or intermediate phenotype of H5. SNP12 (C/T) was the only mutation differentiating the resistant haplotype from the susceptible ones. Combined analysis of the 10 markers resulted in dividing the major haplotypes into 118 different sub-haplotypes. Structure and clustering analyses grouped them into two main clusters and seven sub-clusters. Variance between the main clusters represented the largest proportion of the total variation. H2, the only haplotype found in Aegilops tauschii, is the ancestral haplotype and H1 (Lr34+) likely arose after the advent of hexaploid wheat. Analysis of geographical distribution showed that H1 was more frequent in the Asian germplasm while H2 dominated the European germplasm. Lr34, a gain-of-function mutation, is hypothesized to have originated in Asia.
KeywordsLr34 Leaf rust Triticum aestivum Haplotype Puccinia triticina
The authors are grateful to Elsa Reimer and Andrzej Walichnowski for technical support, Braulio Soto-Cerda for help with the Structure analysis and Michael Shillinglaw for figure preparation. AD was supported by Monsanto’s Beachell-Borlaug International Scholarship Program (MBBISP).
- Benham J, Jeung JU, Jasieniuk M, Kanazin V, Blake Y (1999) Genographer: a graphical tool for automated fluorescent AFLP and microsatellite analysis. J Agric Genome 4:3Google Scholar
- Borghi B (2001) The world wheat book: a history of wheat breeding, Italian wheat pool. In: Bonjean AP, Angus WJ (eds) Intercept. Lavoisier Publishing, Paris, France, pp 289–309Google Scholar
- McCallum BD, Cloutier S, Hiebert C, Jordan M (2009) Leaf tip necrosis co-segregates with seedling leaf rust resistance conditioned by Lr34 at low temperatures. In: Proceedings of the 12th international cereal rusts and powdery mildews conference, October 13–16, Antalya, TurkeyGoogle Scholar
- Nei M (1973) The theory and estimation of genetic distance period. In: Morton NE (ed) Genetic structure of populations. University of Hawaii Press, Honolulu, pp 45–54Google Scholar
- Peterson RF, Campbell AB, Hannah AE (1948) A diagrammatic scale for estimating rust intensity of leaves and stems of cereals. Can Res Sec C 26:496–500Google Scholar
- Singh RP, William HM, Huerta-Espino J, Rosewarne G (2004) Wheat rust in Asia: meeting the challenges with old and new technologies. In: Fisher T (ed) Proceedings of the 4th international crop science congress, new direction for a diverse planet. BPA Print Group Pty Ltd, Gosford, pp 1–13Google Scholar
- Sneath PHA, Sokal RR (1973) Numerical taxonomy: the principles and practice of numerical classification. WH Freeman, San FranciscoGoogle Scholar
- Spielmeyer W, Singh RP, McFadden H, Wellings CR, Huerta-Espino J, Kong X, Appels R, Lagudah ES (2008) Fine scale genetic and physical mapping using interstitial deletion mutants of Lr34/Yr18: a disease resistance locus effective against multiple pathogens in wheat. Theor Appl Genet 116:481–490CrossRefPubMedGoogle Scholar
- Wicker T, Krattinger SG, Lagudah ES, Komatsuda T, Pourkheirandish M, Matsumoto T, Cloutier S, Reiser L, Kanamori H, Sato K, Perovic D, Stein N, Keller B (2009) Analysis of intraspecies diversity in wheat and barley genomes identifies breakpoints of ancient haplotypes and provides insight into the structure of diploid and hexaploid Triticeae gene pools. Plant Physiol 149:258–270CrossRefPubMedCentralPubMedGoogle Scholar
- Yeh FCR, Yang TJ, Boyle Z, Ye J, Xiyan M (2000) PopGene32, Microsoft Windows-based freeware for population genetic analysis, version 1.32. Molecular Biology and Biotechnology Centre, University of Alberta, EdmontonGoogle Scholar