|Kolmer, James - Jim|
Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2012
Publication Date: 6/1/2012
Citation: Kolmer, J.A., Hanzalova, A., Goyeau, H., Bayles, R., Morgounov, A.I. 2012. Genetic differentiation of the wheat leaf rust fungus Puccinia triticina in Europe. Plant Pathology. Available: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3059.2012.02626.x. Interpretive Summary: Wheat is attacked by the leaf rust fungus for which the scientific name is Puccinia triticina. The disease leaf rust of wheat occurs in the U.S. and also in Europe and world wide. The purpose of this study was to genetically characterize the P. triticina population in Europe (Great Britain, France, Czech Republic, Hungary, Italy, Turkey, Spain) using DNA based molecular markers and also by testing the P. triticina isolates for their ability to attack different resistance genes in wheat. 122 isolates of P. triticina from Europe were placed into eight genetically distinct groups. Seven of the groups were of isolates that could attack bread wheat, while one other group of isolates could attack durum (pasta) wheat cultivars. The DNA patterns of the isolates from Europe will be used by USDA-ARS scientists to compare P. triticina populations in the U.S. and world wide to determine how this fungus migrates around the world, and to determine the origin of any new biotypes of the fungus that may be found in the U.S. Information on the origins and migration of P. triticina biotypes can be used by wheat breeders and plant pathologists to develop wheat cultivars that are resistant to leaf rust, thus reducing yield losses to this disease.
Technical Abstract: Leaf rust, caused by Puccinia triticina is a common disease of wheat in Europe. The objective of this study was to determine whether genetically differentiated groups of P. triticina are present in Europe. In total, 133 isolates of P. triticina collected from western Europe, central Europe, and Turkey were tested for virulence on 20 lines of wheat with single leaf rust resistance genes, and for molecular genotypes with 23 simple sequence repeat (SSR) markers. After removal of isolates with identical virulence and SSR genotype within countries, 121 isolates were retained for further analysis. Isolates were grouped based on SSR genotypes using a Bayesian approach and a genetic distance method. Both methods optimally placed the isolates into eight European (EU) groups of P. triticina SSR genotypes. Seven of the groups had virulence characteristics of isolates collected from common hexaploid wheat, and one of the groups had virulence characteristics of isolates from tetraploid durum wheat. There was a significant correlation between the SSR genotypes and virulence phenotypes of the isolates. All EU groups had observed values of heterozygosity greater than expected and significant fixation values, which indicated the clonal reproduction of urediniospores in the overall population. Linkage disequilibria for SSR genotypes was high across the entire population and within countries. The overall values of RST and FST were lower when isolates were grouped by country, which indicated the likely migration of isolates within Europe. The European population of P. triticina had higher levels of genetic differentiation compared to other continental populations.