| Common bermudagrass (Cynodon dactylon) is widely cultivated as the warm-season turfgrasses in the world. There is abundant native bermudagrass germplasm in China with great potential of utilization.After a whole investigation in ecological distribution areas and growth habits of bermudagrass populations,33 typical wild bermudagrass accessions and 25 introduced cultivars of different countries more than 800 of the collection from the typical habitat were selected as experimental materials, of which contained 19 representational provinces and four countries, which included China, USA, Austrilia, and India. In view of their abundant variation and genetic diversity between domestic accessions (cultivars) and aboard cultivars, systematic studies on diferent levels had been made on morphology and DNA markers in order to supply the theoretical base of bermudagrass genetic improvement. In the comprehensive evalution, this study preliminary analysised the inter-relationship and variation of the green, turf quality, and stress resistance, which included drought and cold resistance, on domestic accession (cultivars) and aboard cultivars; excellect accessions had been selected in order to supply foundation for the development, utilization, and breeding new cultivars. The main research contents and results were as follows:1. The comparative study on diversity of domestic abroad bermudagrass germplasm base on morphology and growth characteristicsThe study is to utilize 10 morphological indexs, green period, and turf quality, in order to preliminary assessment genetic variation of morphological characteristic among 55 common bermudagrass accessions. The results were as fellows:①there is rich diversity in morphological index, green period, and turf quality of bermudagrass from domestic and aboard, the highest of the variant coefficient is the air of rear leaf, which is 144.3%, the lowest is green period, which is 6.3%, the average of all variation is 45.7%; ②the domestic accessions are higher variation than the aboard accessions, of which the variation coefficient of domestic accessions was from 7.0% up to 154.1% and average 47.2%, and the variation coefficient of aboard accessions from 5.0% up to 130.3% and average 42.9%; ③the accessions with higher turf growth always boast higher reproductive branches, longer leaf blades, and high density of inflorescencs; thought all these leads to thick internodes, pale-green leaves and less developed stolons.④the accessions of C. dactylon could be divided into 3 morphological groups by means of UPGMA, that is, The 1st group: no inflorescencs; the 2nd group:intermediate; the 3rd group:reproductive sticks and nutrition are very high sticks the type of seed yield higher.The study is to utilize five asexual reproductive traits, which are coefficient of expansion, level growth rate, vertical growth rate, the number of stolon per unit perimeter and the longest stolon, in order to preliminary assessment genetic variation of asexual reproduction characteristic among 55 common bermudagrass accessions. The results were as fellows:there is rich diversity in asexual reproduce of bermudagrass from domestic and abroad, the variant coefficient was from 35.10 up to 82.31% and average 57.26%. There existed significant correlations among asexual reproduction-related characters of bermudagrass in domestic and abroad except vertical growth rate, the maximal correlations coefficient was 0.957; Bermudagrass accessions can be divided three asexual reproduction types based on the five characters by means of SPSS 13.0, that is, rapid propagation of stolon, intermediate and low-speed reproduction of stolons. Among them, domestic accessions have characteristers of the rapid propagation of stolons.The study is to utilize ten seed reproductive quantitative traits, which are inflorescence density, the number of branches of inflorescence, a high degree of reproductive sticks, each small ears, etc., in order to preliminary assessment genetic variation of seed reproduction characteristic among 53 common bermudagrass accessions. The results were as fellows: diversity in reproduce of bermudagrass in domestic and abroad were discovered, the variant coefficient was between 8.09% and 60.00%, the average of variant coefficient was 23.71%. There existed significant correlations among reproduce characters of bermudagrass in deomestic and abroad, the maximal correlations coefficient was 0.620.53 bermudagrass accessions of domestic and abroad can be divided three reproduce types based on the ten characters by means of UPGMA, that is, The 1st group:high seed production, high reproductive sticks, high nutrition sticks and low reproductive sticks high degree of the type of relatively high; the 2nd group:height of grass and sticks a high degree of double-low reproductive the type of seed production and relatively low; the 3rd group:reproductive sticks and nutrition are very high sticks the type of seed yield higher. Among them high seed output has the germplasm which can cultivate cultivating the good seed type latent productive capacity. This study could provide as a reference for further utilization of China bermudagrass germplasm.2. The comparative study on diversity of domestic abroad bermudagrass germplasm base on molecular levelThe study was conducted to assess molecular genetic variation and relatedness among 55 common bermudagrass accessions. SRAP markers were used. Thirty selected from 90 SRAP primer combinations generated a total of 274 clearly scorable bands encompassing 268 polymorphic. Percentage of polymorphic loci (PPL) for the domestic and introduced accessions was 93% and 83%, respectively. Cluster analysis by UPGMA based on the polymorphic markers indicated three distinct clusters. Coefficients of genetic similarity (GSC) among the genotypes ranged from 0.57 up to 0.97. Genetic diversity estimate, He, for the domestic accessions and introduced cultivars was 0.26 and 0.24, respectively.A collection of 55 common bermudagrass accessions have been screened with 38 SSR primer pairs in order to analyze their genetic diversity.88 bands were amplified by 9 informative and reliable primers, of which 86 were polymorphic loci (97.7%). The He and Shannon genetic diversity phenotype index (I) were 0.29 and 0.43, respectively. It was revealed that the degree of genetic diversity of three regions in descending order was wild accessions, USA cultivars, China cultivars, and Australia cultivars using PPL, Nei’s genetic diversity and Shannon index. UPGMA cluster analysis of the GSCs data grouped the bermudagrass accessions according to their original information. The present study verified that wild bermudagrass accessions have rich genetic diversity, which is an excellent basis for bermudagrass breeding for new cultivars.236 bands were amplified by 23 primers, of which 10.3 bands per primer. PPL for all accessions was 86.9%. GSC among the genotyes ranged from 0.58 up to 0.97. He was 0.27 in average. PPL for the domestic and introduced accessions was 83% and 82%, respectively. Analysis of cluster showed that all the 55 accessions could be distinguished by ISSR markers and divided into 3 groups according to UPGMA method. The results also showed that the genetic diversity in bermudagrass accessions based on ISSR genetic similarity was correlated with geographic distribution. Compared with SRAP and SSR markers, ISSR marker had lower amplication potencial in bermudagrass accessions, and only 23 of 88 primer conbinations could amplified distinct products; but average polymorphic bands per primer was higher than SSR and SRAP marker. UPGMA dendrograms for bermudagrass accessions based on GSCs of three kinds of molecular markers were not the same, but they all could reflect rather similary distribution pattern of genetic relation. Therefore, SRAP, SSR, and ISSR all could be applied to detect genetic diversity for C. dactylon.3. The evaluation of abiotic stress resistance of excellent accessionsThe evapotranspiration (ET) and cold resistant of 20 excellect accessions of domestic bermudagrass, which included 10 introduced cultivars, such as’Xinnong No.1’(C794), Tifton 10’(C746),’Nanjing’(C106),’Yangjiang’[C291(1)], were evaluated. The results showed that there were significantly differences on ET among 30 tested accessions, ET values ranged from 0.740～1.707 mmol·m-2·s-1. The average coefficient variation for all accessions was 22.17%. There were 2 accessions had lower ET than the 7 check cultivars. The average ET of five groups ranked from high to low in an order as wild accessions, all of accessions, native accessions, aboard cultivars, and control accessions. Domestic accessions (24.39%) and aboard cultivars (14.51%) had the largest and lowest variation coefficient on ET, respectively. There were significant differences on ET among intragroups accessions in native accessions and aboard cultivars. An extremely significant linear correlation relationship of dual regression analysis was demonstrated between the ET in wild accessions and longitude and latitude, and ear of leaf, respectively.The results of cold resistant were as fellows:the Semi-Lethal temperature (LT50) of bermudagrass accessions ranger from-6.57 to-0.29℃, average of-2.62℃, and coefficient of variation of 70.23%, which indicated quite large cold tolerance differences between accessions; There was no significant linear correlation between LT50 of bermudagrass accessions and longitude and latitude, and binary regression analysis has also no significant linear correlation; The LT50 and leaf length, leaf width, hair on leaf surface and hair on leaf back for correlation analysis showed that LT50 and leaf length, leaf width reached a negative correlation, leaves wide reach a significant negative correlation, there are the weak performance between positive correlation between LT50 and hair on leaves. Finally, this study for bermudagrass future breeding and lay the foundation for development and utilization.The lower of LT50 on bermudagrass accessions were 788 (-5.59℃), C089 (-3.53℃), C461 (-3.51℃), C737 (-3.87℃), C810 (-4.71℃), and C610 (-4.33℃); and the lower of ET of accessions are C788, C189(1), C291, and C177.4. The fingerprint construction of excellent accessions and cultivarsThe SRAP analytic system was set up and applied to cultivars identification and genetic diversity in this study for the first time. Twenty-four bermudagrass cultivars, which came from China, USA, and Australia, were screened by SRAP technique with 90 primer combinations.In the analysis,30 primer combinations produced stable and reproducible amplification patterns. Among the total 274 amplified fragments,249 (91%) were polymorphic, with an average of 9 fragments for each prime combination ranging in size from 100 up to 500 bp. Thirteen fragments of the total 274 were amplified by the primer combination, Me5-Em7. The DNA fingerprints were then converted into binary codes with 1 and 0 representing the presence and absence of the corresponding amplified fragment, respectively. On the DNA fingerprints, each bermudagrass cultivar has its unique binary code and can be distinguished from the others. The 274 fragments were used to develop a dendrogram with UPGMA, and the 24 cultivars were divided into three major groups at the 0.69 similarity level. The coefficients of genetic distance among the varieties ranged from 0.57 up to 0.97. He was 0.27 in average. This is the first report on the development of SRAP technique and its utilization in molecular identification and genetic analyses of bermudagrass cultivars. The results demonstrated that SRAP marker is a stable, simple, polymorphic, and reproducible molecular marker technique for identification of bermudagrass cultivars and their genetic relationships, which may provide basis for the genetic breeding in the future.One SRAP primer combination with stable amplification profiles were selected from 90 pairs of SRAP primers and the DNA fingerprint of nineteen new strains (cultivars) of common bermudagrass were established. PCR products were detected by rapid silver staining procedure in non-denaturing poly acryl amide gels and by DNA fingerprinting of tested materials. DNA fingerprints, were converted into binary code with 1 and 0 representing the presence and the absence of corresponding amplified fragments, respectively, which were used for reference and 19 domestic strains (cultivars) were distinguished from the popular cultivars C. dactylon ’Yangjiang’, C. dactylon’Tifton 10’, C. dactylon’Xinnong No.1’, and C. dactylon ’Nanjing’ at a molecular level, and could distinguish among those good accessions. Finally,19 accessions were analysed by thirty selected from 90 SRAP primer combinations, and the accessions were classified into two groups by the coefficients of genetic distance method using NTSYS-pc software. |
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