| Due to the seriously genetic erosion and usefulness for minor parents over a long time in the bread wheat production and breeding programs, the genetic diversity of wheat cultivars and lines in China as well as in the whole globe has come out more and more decreasing gradually. A vast of study results demonstrated that narrow genetic basis of wheat resources has become a limiting factor in the process of the wheat yields and quality improvements and therefore, enhancing genetic diversity of wheat resources is the key for lessening biotic and abiotic frangibility. On the other hand, because of possessing mass of useful genes and rich genetic variations, wild relative of wheat has played an important role in the process of improving the genetic basis of bread wheat, the exploitation and utilization to key genes in wild relative of wheats is significant to broaden the genetic basis of wheat breeding and sustainable wheat production.Four synthetic hexaploid wheats(SHW) of Syn768, Syn769, Syn780 and Syn786 from CIMMYT, five bread wheat(BD) commercial cultivars and lines widely grown in Chengdu plain in Sichuan province of China and 117 lines derived from the crosses of SHWs×BDs above(Chuanmai 38, Chuanmai 42, Chuanmai 43 and Chuanmai 47 have been authorized for commercial cultivars) were studied for their genetic diversity by SSR marker at the level of DNA; and several functional genes such as semi-dwarfing gene Rht8, polyphenol oxidase gene and Waxy protein subunit genes which affecting agronomic trait and flour qualities were molecularly detected; and utilization of SSR markers PCR-based was validated for the molecular marker-assisted selection. The major results were summarized below:1. Four SHWs of Syn768, Syn769, Syn780 and Syn786, five BD commercial cultivars and lines and 117 backcross-derived lines(DLs) from the crosses of SHWs×BDs above were analyzed using 37 wheat microsatellite markers(among which, 13, 12, and 12 primer pairs belonging to the A, B and D wheat genome, respectively) to explain the potential genetic diversity in wheat breeding programs. Totally 256 alleles were detected on these microsatellite primer pairs, with an average of 6.92 alleles per locus. The polymorphic information content(PIC) and Simpson index(SI) showed that the values of A genome (0.6145, 1.1874)＞the Bgenome (0.5346, 1.081)＞the D genome (0.4276, 0.8046). The mean genetic similarity(GS) coefficients of the A, B and D genome were 0.3797, 0.4627 and 0.5815, respectively, and fromwhich it indicated that there were the intermediate genetic diversities among the derived lines from the crosses of synthetic hexaploid wheats and bread wheats. The UPGMA clustering analysis, based on a similarity matrix by a simple matching coefficient algorithm at three genomes, delineated that their dendrograms were different; it indicated that the genetic diversities of the derived lines from the synthetic hexaploid wheats were different on different genomes in which the genetic diversitiesof D genome was mostly poor and the genetic diversities of A genome was mostly rich. 2. The PCR amplified products of 192bp allelic variational fragment at the locus Xgwm261 could be used as its diagnostic molecular SSR marker. The total frequency of Rht8 genotype is 77.78％in the detected derived-populations from Syn768, Syn769, Syn780 and Syn786. The frequency of Rht8 genotype of the population from Syn768 is 96.70％as the highest one, and the one from Syn769 with 71.64％is the lowest, and for the population from Syn780, its frequency of Rht8 genotype is 73.68％with a close ratio of 3: 1 and the cultivar Chuanmai 47 from Syn786 is absent from the gene Rht8. The inheritance of the dwarfing gene Rht8 is randomly separated, and the results from Rht8 genotype of progeny from crosses of synthetic hexaploid wheat and bread wheat were similar to the one from studies on bread wheats.3. PPO genotypes were detected by specific-primer PCR amplification and modified PAGE. The results showed that the SSR marker at Xgwm312 locus for the 117 synthetic derived cultivars and advanced lines produced four polymorphic fragments with alleles of 198bp, 216bp, 232bp and 240bp. Of 113 lines, there were 65 with 198bp allelic fragment, 13 with 216bp allelic fragment, 35 with 232bp allelic fragment and 4 with 240bp allelic fragment. The allelic fragment distributional frequencies were different between the four synthetic derived advanced line populations. The results revealed that the gene PPOis randomly segregated into offspring and significantly relative to parental genotypes, A novel variation with 240bp allelic fragment which was not existed in the parents was observed in present experiment.4. Waxy protein subunits were tested by specific-primer PCR amplification and modified PAGE. The results showed that 8 of these cultivars and lines were thenull Wx-B1 type and null frequency was 6.6％, what is more, there was no other null types existing in the materials detected. The null frequency was different between the population from the three parents of synthetic hexaploid wheats. From this study, it could be concluded that the study on Waxy genotype of progeny from crosses of synthetic hexaploid wheat and bread wheat can provide useful information for improving bread wheat and be a useful tools for marker-assisted selection of wheat breeding programs.5. The molecular detection of 125 genotypes to semi-dwarfing genes Rht8, PPO gene and Waxy protein subunits showed that, if the pedigree of a wheat cultivar was known, the three molecular markers and the PCR marker based on PCR could be applied to examine and screen genotypes in the molecular marker-assisted selection so that it could promote efficiency in breeding programs.The above results indicated that 117 synthetic hexaploid wheat backcross-derived lines possess mass of useful genes, and have rich genetic variations, all of which are the important gene pool. Hexaploid wheats evaluated in the present study could be utilized to improve cultivated wheat as important gene pool for the molecular markerassisted selection. |
PDF Full Text Request