| Carpetgrass [Axonopus compressus (Sw.) Beauv.] is an important warm-season perennial turfgrass native to southern America that is widely used in tropical and sub-tropical areas.In China, the wild germplasm resources of Axonopus compressus are mainly distributed in Hainan, Fujian, Guangdong, Guangxi, Yuannan and Guizhou. Previous studies of A. compressus mainly focus on germplasm investigation and physiological characteristics, however, the genetic diversity of its wild germplasm resources has been rarely explored. Therefore, the study we examined the genetic diversity of carpetgrass germplasms using morphological markers and molecular markers. Combined with morphological markers and habitat characteristics, genetic characteristics for carpetgrass provide a more comprehensive theoretical reference, and provide the basis for screening high quality new strain. The main conclusions are as follows:1. Study on the morphology diversity of carpetgrass germplasmsInternode length, inflorescence diameter were significantly difference (P<0.05), while the other traits were highly significantly difference (P<0.01), this study show that carpetgrass has rich genetic diversity. The variant coefficient of338.64%for internode length was the highest in all morphology characteristics, but the leaf length of the creeping shoot of20.79%was the lowest, the average was111.17%. The coefficients between morphology characters of64carpetgrass accessions were significantly (P<0.05) or highly significantly (P<0.01).2. Genetic diversity analysis of carpetgrass germplasms based on ISSRTwenty-five primers were selected from100ISSR primers, and208clearly bands were amplified from the64materials, the average number of bands was9.9per primer, and the percentage of polymorphic bands was196(94.7%). Cofficients of genetic similarity among64accessions ranged from0.46to0.99.3. Genetic diversity analysis of carpetgrass germplasms based on SRAPTwenty-seven SRAP primer combinations generated a total of691distinct bands,668(96.67%) of which were polymorphic. The number of observed alleles ranged from16to35, with an average of25.6. Coefficients of genetic similarity among the accessions ranged from0.52to0.82.4. Microsatellite markers developed for carpetgrass germplasmsIn this study, we used Roche454pyrosequencing combined with magnetic bead enrichment method of FIASCO to isolate SSR markers from A. compressus genome. A total of1942microsatellite loci were identified53,193raw sequencing reads. One hundred microsatellite loci were selected to test the primer amplification efficiency across24individuals,14primer pairs yielded polymorphic amplification products. The number of observed alleles ranged from2to6with an average of3.5. Shannon’s Information index ranged from0.169to0.650with an average of0.393. Nei’s genetic diversity ranged from0.108to0.457with an average of0.271.5. Genetic diversity analysis of carpetgrass germplasms based on SSRFourteen SSR primer combinations generated a total of49distinct bands,48(97.96%) of which were polymorphic. The number of observed alleles ranged from2to6, with an average of3.5. Coefficients of genetic similarity among the accessions ranged from0.24to0.98. UPGMA clustered the64accessions into three groups, and not all samples from the same region belonged to the same group.6. The comprehensive analysis of the three markers (ISSR+SSR+SRAP)The study on the genetic diversity of64carpetgrass accessions was analyzed based on the integrated SSR, SRAP and ISSR markers data. The SSR and ISSR integrated date showed a high correlation between the similarity coefficients matrix (Mantel test:r=0.8237), which meant ISSR and SSR were high similarity to each other, while the correlation value bewteen the SRAP and SSR, SRAP and ISSR the similarity coefficients matrix was low (0.7541and0.7253). The64carpetgrass accessions were classified into three groups based on the SSR、SRAP and ISSR integrated date, the results revealed by ISSR and SSR were similar, but the polymorphic bands of SSR were higher than ISSR. |
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