| With the development of industry and the wide uses of chemical fertilizer in sewage irrigation, the soil pollution have been more and more serious in these years. The enriched salt ions severely decrease the agricultural production and cause a waste of the soil resources. Considering there are about 80% of salt soils still not be used, the researches of developing new solutions for this problem are required. The AM symbioses, was known as forming a relationship between soil fungus and vascular plants, has a long history of 4 million years, and about 80% of all vascular land plants are able to form this symbioses, which enhanced their adaption to harsh adverse conditions.In this study, the Astragalus sinicus was used as the test host, and Glomus mosseae. Glomus intraradices were used as the AM fungus. The specific primers were designed based on the specific sites found in the sequences of LR1 and NDL22. The specificity of the three primers was verified by PCR method. In this study, the correlation curves between the value of DNAAMF/DNAplant and fungal colonization of the root system by means of TB stain method were established, the qPCR method could be used to detect the AM fungal colonization rate under the condition of mix inoculation reliably. It can result in qualitative and quantitative testing for AM species and colonization rate over mixed-species. This method was used to detect the effect of different level of salt and phosphorus on colonization of AM fungus to Astragalus sinicus L, carried out with a greenhouse experiment. Plants were grown at three salt levels and three phosphorus levels, the colonization of each fungi and the interaction between them were detected using the qPCR method, the biomass of the plant, the concentrations of K+, Na+ and P, as well as the distribution of Na+ were measured. The results were as follows:1) The level of mycorrhizal colonization measured by qPCR correspond to the microscopical analysis of stained roots, and the percentage of mycorrhizal colonization and the level of rDNA correlated clearly (G. mosseae, R=0.9676*; G. intradices, R=0.9618*), which suggest that the qPCR method could be used to assess the actual colonization directly.2) The results of greenhouse experiment showed that:salt stress reduced the colonization of AM fungus under each given NaCl levels, the reduced extent was different under different P levels, while under low level of P, middle level of P and high level of P, the salt concentration was 1.05 g/kg, compared with low salt concentration(Og/kg), the colonization of Glomus intraradices was declined as 61.59%, 28.07%,15.46% respectively, and 21.5%,31.56%,52.08% for Glomus mosseae respectively. Under given high phosphorus, Glomus intraradices had more ability to resist salt stress. The added P could alleviate the salt stress on Glomus intraradices, but reduce the colonization of Glomus mosseae even more. Glomus mosseae nearly couldn't infect the roots under high salt level.3) The mycorrhizal effect was different under different environments; different AM fungus had different responses to salt and P. In this experiment Glomus intraradices was more tolerant than Glomus mosseae at all salt levels. Mycorrhizal plants maintained higher root and shoot dry biomass. Concentrations of P and K+ were higher than non-mycorrhizal plants under given NaCl and P levels. AM fungus helped the host plants to abort more potassium and decline the transport of sodium from roots to shoots so as to alleviate the salt stress. Summary, qPCR could be used to detect the DNA amount of AM fungus in roots, which lead to the quantitative study and qualitative study in mycorrhizas. The symbiosis formed between AM fungus and Astragalus sinicus, Glomus intraradices has a higher resistance to salt stress, so this AM fungi can be used for mycorrhizoremadiation of salt pollution. |
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