|Kolmer, James - Jim|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2011
Publication Date: 6/15/2011
Citation: Kolmer, J.A., Ordonez, M.E., Manisterski, J., Anikster, Y. 2011. Genetic differentiation of Puccinia triticina populations in the Middle East and genetic similarity with populations in Central Asia. Phytopathology. 101:870-877. Interpretive Summary: The wheat leaf rust fungus that is called Puccinia triticina is an important disease of wheat in the USA and also worldwide. The leaf rust fungus is highly variable, as many different forms of the fungus are found that differ for their ability to attack different leaf rust resistance genes in wheat. DNA based molecular markers have also been used to characterize genetic variation in the leaf rust fungus. The purpose of this study was to characterize collections of the wheat leaf rust fungus from the Middle East (Egypt, Israel, Turkey, Ethiopia, Kenya) to determine if genetically different groups are present in this region. Based on DNA markers, there were two major groups of isolates that that differed for DNA markers and were virulent to common wheat cultivars. Leaf rust collections in these two groups were found in all of the countries. The leaf rust collections in these two groups however differed for virulence to leaf rust resistance genes in common wheat. Two other groups of leaf rust that were characteristic of collections from durum wheat were also found. Most of these collections came from Israel, Ethiopia and Turkey. All of the collections from the Middle East were compared with collections from Central Asia for DNA markers and for ability to attack different leaf rust resistance genes in wheat. The two major groups of collections from the Middle East that attacked common wheat were nearly identical to the two groups from Central Asia for the DNA markers. This indicated that leaf rust may be carried in wind currents between the Middle East region and Central Asia. The collections from the Middle East and Central Asia will be compared in a future study with collections from the USA to determine if movement of the leaf rust fungus occurs between these three regions.
Technical Abstract: Leaf rust of wheat, caused by Puccinia triticina is a common and widespread disease in the Middle East. The objective of this study was to determine if genetically differentiated groups of P. triticina are present in the Middle East region and to compare the population from the Middle East with the previously characterized population from Central Asia to determine if genetically similar groups of isolates are found in the two regions. In total 118 isolates of P. triticina collected from common wheat and durum wheat in Egypt, Israel, Turkey, Ethiopia, and Kenya were tested for virulence on 20 lines of wheat with single genes for leaf rust resistance and for molecular genotypes with 23 simple-sequence repeat (SSR) markers. After removal of isolates with identical virulence and SSR genotype in each country, 103 isolates were retained for further analysis. Clustering of SSR genotypes based on two dimensional principal coordinates and virulence to wheat differential lines grouped the isolates into four Middle East (ME) groups. The two largest ME groups had virulence phenotypes typical of isolates collected from common wheat, and two smaller ME groups had virulence typical of isolates collected from durum wheat. All pairs of ME groups were significantly differentiated for SSR genotype based on RST and FST statistics, and for virulence phenotype based on FPT. All ME groups had observed values of heterozygosity greater than expected and significant fixation indices, that indicated the clonal reproduction of urediniospores in the overall population. Linkage disequilbria for SSR genotypes was high across the entire population. The overall values of RST and FST were lower when isolates were grouped by country of origin that indicated the likely migration of isolates within the region. The two ME groups with virulence typical of isolates from common wheat were not differentiated for SSR genotype from groups of isolates from Central Asia based on RST, indicating the possibility of migration of P. triticina between the two regions.