Genetic Diversity Revealed By SSR Markers And Polymorphism Of HMW-GS In Hexaploid Wheat (AABBDD)

Wheat (Triticum. aestivum L) is one of the most important crop in the world, and in China, it is only second to the rice. Due to long-term orientated improvement, the genetic diversity within common wheat is more and more narrow. Because of the normal fertility of hybrids between common wheat and other hexaploid wheat, such as spelt, club wheat and Chinese endemic wheat landraces (T. tibetanum,T. yunnanense,and T. petropavlavskyi), they are thought to be important germplasms for wheat breeding and improvement. In this study, three SSR molecular markers, including genomic-SSR, EST-SSR and chloroplast SSR, were used to measure the genetic diversity between and among the above hexaploid wheat populations. The compositions of high molecular weight glutenin subunits (HMW-GS) were also analyzed. The main results were as follows:1) As compared to genomic-SSR, EST-SSR provides a more accurate evaluation of genetic relationship, especially when accessions are very closely related in pedigree, although the polymorphism of EST-SSR was lower. Therefore, EST-SSR is an ideal marker for the evaluation of genetic diversity in wheat.2) Two SSR molecular markers, namly genomic-SSR and EST-SSR, are used to measure the genetic diversity among common wheat, spelt and compactum. The results show that common wheat has the highest genetic polymorphism, followed by spelt and then compactum. The mean genetic distance between the populations is higher than that within a population, and similar tendency is detected for individual genome A, B and D. As compared with spelt, the genetic diversity between common wheat and compactum is much smaller, indicating a closer consanguine relationship between these two species.3) The genetic diversity between Chinese endemic wheat landraces and other populations of hexaploid wheat was systematically analyzed. As compared with T. petropavlavskyi, T. tibetanum and T. yunnanense are genetically close related to common wheat based on the nuclear genomic microsatellite markers, T. petropavlavskyi is differ from others. In addition, the genetic diversity of chloroplast genome between common wheat and all of Chinese wheat landraces is very small. Another result is that T. tibetanum has abundant genetic variation on genome D.4) It is concluded that the composition of HMW-GS in spelt has its unique character, and T. petropavlavskyi has special HMW-GS at Glu-1D.5) The strategy for improving the genetic diversity of wheat was also discussed in this paper. Meanwhile, the origin and evolution of hexapoid wheat, especially Chinese endemic wheat landrace, was also analyzed and discussed.