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Genetic Diversity Of Rhizobia Isolated From Caragana Intermedia In Maowusu Sandland And Effects Of Symbionts Between Caragana Ssp. And Rhizobia On Ecosystem Functioning

Posted on:2002-07-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:L F GaoFull Text:PDF
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The effects of biodiversity on ecosystem functioning was defined as the first core of five core projects in the action plan of Biodiversity Science. Biodiversity include genetic, species and ecosystem diversity, the genetic diversity is the ultimate source of biodiversity at higher levels. Based on the studies of Caragana ssp. in our lab, 74 strains isolated from Caragana intermedia in Maowusu sandland were analyzed on the basis of genetic and phenetic features, to reveal their diversity. Artificial symbiotic systems were constructed to reveal the effects of different symbionts on the ecosystem functioning. The results were as follows: 1 .Genetic diversity of Caragana rhizobiaStains were clustered into 3 groups analyzed from total cellular soluble protein profiles: group A was composed of nearly all Caragana rhizobia, group B contained all the reference stains, and group C was consisted of only one Caragana rhizobia strain GH72. It was showed from the Est profiles that one band was specific to Caragana rhizobia and other bands shared by all the strains used and Caragana rhizobia and reference strains intertwined.Partial sequence of 16S rDNA and 16S-23S rDNA IGS were amplified and the fragments were larger than those reported before. Digested by four restriction enzymes, all the Caragana rhizobia strains studied were classified into 12 16S rDNA genotypes, showing rich genetic diversity, and 42.4% strains belonged to genotype 2. Comparison with related defined rhizobia, the full length 16S rDNA sequence of GH33 showed high similarity with some Rhizobium species at or above the level of 95%.All the Caragana rhizobia studied could secrete acid substance that was a characteristic of Rhizobium. 33% and 95% strains could utilize lactose and starch as single carbon resource respectively. Besides, Caragana rhizobia had no preference toother carbon substrates tested in this study. 53.8% strains could grow at medium containing 9% NaCl, 75% strains could tolerate acid and alkaline up to pH4.0 and pH 10.0, and 66.7% strains contained activity after exposed to 60C for 10 min. All these data showed Caragana rhizobia had strong adaptability to severe environment. 2.Effects of different Caragana ssp.and rhizobia symbionts on ecosystemArtificial symbiotic systems were constructed on ecosystems of soil covered with sand imitating one landscape of Maowusu sandland and stony arid soil between 14 strains and three Ningtiao species, Caragana microphylla, C. intermedia and C. korshiskii. Based on the biomass of shoots, roots and nodules of each pair of symbionts, C. korshiskii and genotype 2 appeared to be the best symbiotic complex in sandland ecosystem, which showed the rhizobia might be the keystone of Maowusu ecosystem, and the genetic diversity of host and rhizobia had effects on the ecosystem functioning. It was suggested that the potential of optimic symbionts was promising. 3.Silver-stained denaturing polyacrylamide gels to detect the inheritance of RAPD85 F2 progeny (Populus simonii^nigra var.italica) were used to detect the inheritance of RAPD by silver-stained denaturing PAGE. 399 products were obtained using only 9 primers, among which 98 loci appeared polymorphic. By Chi-square analysis of the segregation ratios of RAPD in F2 progeny, 79 loci showed Mendenlian inheritance, composed of 80.6%. It was suggested from genetic analysis that the optimized method used in this study was reliable and effective, which might accelerate RAPD mapping of plants.
Keywords/Search Tags:RAPD, genetic anlysis, Populus, silver-stained denaturing PAGE, Caragana intermedia, rhizobia, 16S rDNA, PCR-RFLP, ecosystem functioning
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