| Cynodon dactylon (Common bermudagrass), the most important member of the gramineous genus Cynodon, is a world-famous warm-season turfgrass and high quality pasture.In view of its diversity in distribution area and growth habits, after a whole investigation of ecological distribution areas and growth habits of bermudagrass populations, a total of 475 bermudagrass accessions including 473 wild accessions and 2 commercial cultivars ('Tifway' and Tifgreen') were selected as experimental materials in this study. In view of their abundant variation and genetic diversity among bermudagrass accessions, systematic studies on different levels had been made on morphological marker and molecular marker in order to supplying the theoretical base of bermudagrass genetic improvement. Meantime, turf and nutrition characteristics of bermudagrass accessions were evaluated through turf quality comprehensive assessment system and nutrition value assessment system. The purpose was to select excellent accessions. The information from this study will be beneficial for the breeding of bermudagrass. The main results were as follows:(1) Seventeen morphological characteristics of 475 bermudagrass accessions were observed and analyzed. Five main results were received as:abundant morphological variation existed in bermudagrass accessions and the coefficients of variation were over 10%. Based on 10 morphological characteristics,475 bermudagrass accessions were clustered into two morphological types, designated as low type and high type.(2) Comparing of lots of DNA extraction method, the improved protocol based on CTAB for isolating total genomic DNA from fresh and healthy leaves of bermudagrass was found.(3) The optimal SRAP-PCR amplification system of C. dactylon was established by employing single factor tests and orthogonal design approaches using young leaves, which came out total 25μL reaction system containing 1.5 mmol/L Mg2+,0.25 mmol/L dNTP,0.4μmol/L primer,1.5 U Taq DNA polymerase, and 80 ng DNA.475 bermudagrass accessions were studied for the analysis of genetic diversity by the optimum SRAP-PCR system. The results indicated that 475 accessions could be separated by 15 primer combinations, and the 15 primer combinations amplified 500 reproducible fragments with an average of 33.33 and all scorable bands were polymorphic in nature and none of the primer combinations used produced monomorphic bands indicating a high level of genetic variation in this grass. GSC among the 475 accessions ranged from 0.554 to 0.964 with an average of 0.723. The accessions were clustered into three major groups by unweighted pair-group method with arithmetic averages.(4) The concentration of Mg2+, dNTPs, Taq DNA polymerase, primers, and DNA which affected the ISSR-PCR reactions was optimized by orthogonal design. Results showed that the optimum system in 25μL reaction mixture was as follows,2.5 mmol/L Mg2+,0.25 mmol/L dNTPs,0.2μmol/L primer,1.0 U Taq DNA polymerase, and 40 ng DNA.The fourteen selected primers amplified a total of 266 scorable fragments among 475 accessions with an average of 19, and the size of the fragments varied from 200 to 3000 bp. The percentage of polymorphic bands was 100%, meaning that the bands were present in at least one accession but were not observed in others. GSC among the 475 accessions ranged from 0.549 to 0.981. The accessions were clustered into four major groups by unweighted pair-group method with arithmetic averages.(5) 50 accessions which had excellent turf characteristics were screened out.14 accessions were more excellent than'Tifway' and'Tifgreen'among them.(6) 32 accessions which had high nutritional quality were screened out.
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