| Genetic Diversity among Sichuan Wheat based on Molecular Markers Masteral student:Zhang Zhi-Qing Supervisors: Zheng You-hang Wei Yu-ming Wu Wei Abstract In this study, the genetic diversity among 40 Sichuan wheat cultivars, which had been popularized above 6.67 X 1 0~ per year in Sichuan Province during recent 50 years, was investigated by using simple sequence repeats (SSR) and sequence-tagged-site(STS-PCR) markers. And the same time, the genetic variations on Glu-1 locus among 40 genotypes have also been investigated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). 1. Using 46 simple sequence repeats (SSR) markers, located on 42 chromosome arms; the genetic diversity was investigated. Thirty-three out of 46 SSR loci (71.74%) were polymorphism. On the 46 SSR loci, a total of 110 alleles have been detected. At each locus, 1 to 8 alleles could be detected, with an average of 2.4. Based on SSR data, the genetic similarity (OS) among 40 Sichuan elite wheat cultivars was calculated. The mean GS was 0.601, varying from 0.451 to 0.767. It indicated that higher genetic diversity was presented in Sichuan wheat cultivars. The variation of GS among different eras revealed that the genetic similarity had the tendency to. increase since 1970. 2. in STS-PCR analysis, 12 of 13 primer sets (92.3%) and 23 of 26 primer-enzyme combinations (88.5%) could reveal polymorphisms. A total of 92 restriction fragments have been detected in these 51 cultivars, with 3.1 fragments per primer-enzyme combination. The genetic similarity varied from 0.478 to 0.989, with the mean of 0.753. The cluster results showed that 40 genotypes could be distinguished by STS-PCR markers. The variation of GS in 5 eras revealed that the genetic similarity had the tendency to increase since 1960. 3. The correlationship result shows that the simple correlationship coefficient between S SR-OS and STS-PCR-GS was significant. (r=0.270). It suggested that the genetic relationship among Sichuan wheat cultivars revealed by SSR and STS-PCR markers were somewhat identical. And, the mean OS value among 40 genotypes based on SSR markers was lower than that based on STS-PCR (0.60 1 vs. 0.753). Moreover, the polymorphic information content (PlC) of SSR and STS-PCR markers varied from 0 to 0.907 and 0 to 0.841, with the mean of 0.498 and 0.483, respectively. All of results suggested that SSR markers could reveal more polymorphic information than STS-PCR markers. 4. The variation of genetic similarity during latest 50 years indicated that the genetic diversity among Sichuan wheat has the tendency to decrease. Thus, in order to broad the genetic foundation of breeding materials, it is necessary to introduce the valuable genes into modem wheat, such as genes of good-quality, high-yield or resistance to disease, to increase the genetic diversity of Sichuan wheat cultivars. 5. The genetic variation at Glu-1 locus among 40 Sichuan elite wheat cultivars was detected by using SDS-PAGE. The high level of genetic variation at Glu-1 locus was observed. Ten subunit patterns and 13 subunit combinations were detected, respectively. The quality scores of each elite cultivar at Glu-1 h... |
