Molecular diversity and genetic structure of modern and traditional landrace cultivars of wheat (Triticum aestivum L.)

Wheat is one of the most important cereal crops of the world. In order to achieve continued genetic gain in wheat improvement programs, an assessment and utilisation of genetic diversity in a wide range of germplasm are required. The Australian Winter Cereal Collection (AWCC, Tamworth) holds over 33 000 accessions of wheat. In this study, we scanned the genome of 1057 accessions of hexaploid common wheat (Triticum aestivum L.) originating from different geographic regions of the world, with 178 polymorphic DArT (TM) markers. These accessions comprised modern cultivars (MCs), advanced breeding lines (BLs), and landrace cultivars (LCs). Our results indicate that the LCs had higher polymorphic information content (PIC values) than the MCs and BLs. Cluster and principal coordinate analysis based on genetic distance matrices enabled classification of the 1057 accessions into 12 subgroups. The structure of subgroups appeared to be geographically determined and was generally consistent with pedigrees. Molecular analyses revealed that LCs have unique alleles compared with MCs and BLs, which may be useful for the genetic improvement of wheat.