Evaluation of geographic distribution of high-molecular-weight glutenin subunits (HMW-GS) in wild and cultivated Triticum species

Variation of high-molecular-weight glutenin subunit (HMW-GS) in 632 wild and cultivated Triticum accessions was investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. A total of 11 alleles of HMW-GS in diploid species, 22 in tetraploid species, and 15 in hexaploid species were detected. Diploid species on Glu-1A locus and tetraploid species Glu-1B locus showed the highest diversity, respectively. Tetraploid species had the highest level of diversity on three Glu-1 loci, followed by hexaploid and diploid, based on Shannon’s information index, Nei’s genetic diversity, and percentage of polymorphic loci. Molecular variance analysis confirmed main variance of HMW-GS within species, regions, and locations, respectively. Variance among species and regions was enhanced gradually with the increase of ploidy. Significant non-random distributions between the phylogenic trees of HMW-GS and the locations of accessions were tested by GenGIS software, indicated that geographic factors played an important role along the different orientations in the spread of Triticum species. We found one original diversified center in diploid what located around Elazig, Malatya, Gaziantep, Urfa, and Kiziltepe in Turkey, and three diversified centers in tetraploid wheat, including Turkey–Armenia–Georgia–Iran, Portugal–Spain, and Ethiopia, respectively, and two diversified adjacent areas between Turkey and Switzerland and around Turkey, Georgia, and Armenia. The original center of diploid species located in southeast Turkey, where the unexpressed 1Ay subunit was mainly distributed in T. urartu, could be one of the candidate regions of polyploidization of Triticum L. The regional distribution of HMW-GS and species also provided geographic evidences for the existence of founder effect on the spread of Triticum species. The present study suggests that integrating genetic diversity with geographic characterization in Triticum could very useful for collection, conservation, and utilization, as well as for research microevolution and domestication.