Monitoring The Effect Of Cadmium Oc Astragalus L. Inoculated With Abuscular Mycorrhizal Fungi

With the development of mineral industry,heavy metal in soil has become one of the most serious problems of the environmental contamination.It has seriously retarded the development of agriculture.Arbuscular mycorrhiza(AM) fungi are a kind of widespread microorganisms which contribute to soil systems,which form mutualistic symbiosis with more than 80%of land plants,not only facilitate plant mineral nutrient uptake,but also enhance tolerance to adverse environmental stress and plant diseases.For the biodiversity and un-culturable separately nature of the AM fungi,it is unable for identification at the species level to discriminate the fungi based on morphology of spores.PCR based on discriminating primer opens the possibility of identifying distinct fungi in the roots and in soil.The aim of this study were:(1) To design the discriminating probes for monitoring the different arbuscular mycorrhizal fungus in mixed community.(2) To investigate the effect of Cd on the development of Glomus mosseae and Glomus intraradices in Astragalus sinicus L..The main results of this study were as follows:Based on the analysis of highly variable region(D1-D2 domain) in 25S rDNA sequence,three discriminating primers gi0,B15 and D10 were developed for Glomus intraradices,HAU-B15 and HAU-D10,respectively.The colonizing mycorrhizal fungi in the mixed community were detected by the application of nested PCR with discriminating primers,which enlarge the area of molecular application in AMF.Compared with un-inoculated treatments,the inoculation of arbuscular mycorrhizal fungi significantly increased the plant growth under Cd stress in this experiment.Glomus moseeae showed high activities of SDH and ALP at 7 weeks even under highest Cd stress.Furthermore,the plants inoculated with Glomus moseeae accumulated eighty nine percent of absorbed Cd in plant root,without transporting to the shoots.It significantly decreased the Cd content in the soil and reduced the toxicity to plants.Nested PCR was performed on the ALP active roots with discriminating primers.The colonization efficiency of Glomus mosseae was not influenced by the presence of Glomus intraradices,while the efficiency of Glomus intraradices colonization was weakly enhanced in the mixed inoculation.However, Glomus moseeae is still the predominant activist in the mixed population.In conclusion,the inoculation of Glomus mosseae showed higher tolerance to Cd stress.It plays an important role in the phytoremediation for Cd contaminated soil. The combination of nested PCR and ALP-activity stained roots,which joined the merits of vital stains and molecular technology together,successfully monitored the efficient fungi in mixed population under Cd stress.