| Based on the field investigation on ecological distribution and growth habits of Cynodon dactylon populations in Southwest of China, thirty-six wild accessions were collected from this area and tested in assessment of genetic variation according to AFLP and SSR molecular markers.Simultaneously, Take "Tifway" as the comparison,three wild accessions were collected for Cold hardiness exercise in 8℃/4℃(day and nights),to determine and analyzing its correlative index.In order to Provide the theory of studying the breeding and exploitation of C.dactylon germplasm in reasonable. Main results obtained are as follows:1. Amplified fragment length polymorphism (AFLP) molecular markers were applied to detect the genetic variation of 36 agrestal accessions of C.dactylon collected from Yunnan, Chongqing, Guizhou, Tibet and Sichuan in China. The following results were obtained,A total of 462 bands were amplified by ten AFLP primer pairs from C.dactylon genetic DNA, among which 452 (97.64%) bands were found to be polymorphic.The AFLP-based genetic similarity values among 44 C.dactylon accessions ranged from 0.67 to 0.95,and the average Nei's coefficient was 0.78.Analysis of cluster and principal component analysis showed that all the accessions could be distinguished by AFLP markers and divided into 4 groups, accessions from the same area were almost classified into the same group associated with their geographical distributions. Genetic differentiation between and within five eco-geographical groups of C. dactylon was estimated by Shannon's diversity index, which showed that 49.35% genetic variance existed within group, and 50.65% genetic variance was among groups. Analysis of cluster in every eco-geographical group by Shannon's diversity index showed that they own significant relationship with the origin regions of accessions. Therefore, complex geographical ecological environment is important factor to the genetic diversity and geographical distribution of Cdactylon.It will own great significance in constituting the scientific protected strategy, promoting its exploitation and utilization, and breeding new varieties.2. Simple sequence repeat (SSR) molecular markers were used to detect the genetic variation of 36 wild accessions of C.dactylon collected from Yunnan, Chongqing, Guizhou, Tibet and Sichuan in China. Eighteen primer pairs produced 353 polymorphic bands, among which 267 bands were found to be polymorphic.averaged 19.61 bands per primer pair. The percentage of polymorphic bands was 75.10%.The Nei's genetic similarity coefficient of the tested accessions ranged from 0.63 to 0.96, and the average Nei's coefficient was 0.75. These results showed that the test resources have ample genetic variation. Analysis of cluster showed that Thirty six wild accessions could be divided into 5 groups. accessions from the same area were almost classified into the same group, The findings implied that there was a kind of correlation among the wild resources, geographical and ecological environment.Genetic differentiation between and within five eco-geographical groups of C. dactylon was estimated by Shannon's diversity index, which showed that 64.77% genetic variance existed within group, and 35.23% genetic variance was among groups. Analysis of cluster in every eco-geographical group by Shannon's diversity index showed that they own significant relationship with the origin regions of accessions. The results provided a scientific basis for the conservation and use of the wild resources of C.dactylon.3. Amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) molecular markers were applied to detect the genetic variation and geographical differentiation of thirty-six wild accessions of C.dactylon collected from Southwest China. The two molecular markers all showed the ample genetic diversity and geographical differentiation of the tested Germplasm. The study also testified the validity and feasibility of these two kinds of molecular markers in analysing C.dactylon's genetic variation, they could be used in genetic diversity testing for wild accessions of C.dactylon extensively. In this paper, two kinds of molecular markers' correlation were analysed, It showed that the correlative coefficient between their genetic similarity coefficient was: r=0.6245, p=0.01.The result indicated that two molecular markers'correlation was remarkable.4. Three wild accessions were collected for cold hardiness exercise in 8℃/4℃(day and nights).Fourteen days' later,taking the unexercised material as the comparison,the test material were carried out the cold intimidation under the temperature grads of 0℃,4℃, 8℃and were determined its correlative index.Then they were transplanted in the cropland to observe its cold hardiness of field.Through measured its half lethal temperature(LT50),the praline content,the MDA content,the soluble sugar content and the field hibernation rate,we can come to the conclusion that the cold exercise could increase the wild C.dactylon Germplasm's cold hardiness.
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