Effect Of Arbuscular Mycorrhizal Inoculation On The Growth, P And As Absorption Of Astragalus Sinicus L. Under Arsenic Stress

In recent years, with the development of ore mining, metal smelting and the application of arsenic compounds in agriculture and industry, arsenic contamination has been a very prominent global environmental problem and remained to be resolve urgently. Plants growing on arsenic polluted soils tend to be mycorrhizal and mycorrhizal fungi can enhance arsenate resistance of the host plants, so mycorrhizal fungi may play an important role in revegetation and phytostabilization of the arsenic contamination soil.The same host plant is often colonized by multiple AM fungus in the natural environment, therefore qualitative and quantitative analysis of the AM fungus in the roots plays a very important role in research on the interaction between plants and AM fungi or between the AM fungus. Conventional staining and nested PCR technology can not do that, but the appearance of fluorescence quantitative PCR technology is expected to overcome these deficiencies.In this paper, a new method using quantitative PCR technology to detect AM fungal DNA for qualitative and quantitative analysis was established and the correlation between the results from quantitative PCR and the colonization was also analysed. The role of different AM fungus and P application on growth, P and As absorption of Astragalus sinicus L growing in As polluted soil were studied by a pot experiment, and the colonization of AM fungi was quantificated using quantitative real-time polymerase chain reaction technique(real-time PCR).The results showed that:the primers designed had high specificity and sensitivity,and the quantity of AM fungal DNA detected by quantitative PCR has a high correlation with colonization rate, so the technology can be successfully applied to the qualitative and quantitative analysis for AM fungi in root segment. In the pot experiment, Gmosseae had more activity than Gintraradices under arsenic stress, and had dominant position in the coinoculation. As the concentration of arsenic increased, the colonization of Gintraradices decreased significantly while that of Gmosseae was less pronounced.However,the increase of phosphorus level inhibited the colonization of both Gintraradices and Gmosseae. Compared with uninoculated controls, AM plants had much higher biomass, P concentration, total P, P/As and lower As concentration. Futhermore, Gmosseae had more positive effects than Gintraradices on promoting growth and detoxification, coinoculation in the middle. With the increase of soil As concentration, the root P concentrations and As concentrations were increased gradually in both inoculated and uninoculated plants. However, the shoot P concentrations in the inoculation treatment did not change significantly, while in the uninoculated controls showed a downward trend; the shoot As concentration in the inoculation treatment showed no significant difference while in uninoculated controls increased. Furthermore, whether inoculated or uninoculated plants, the As concentrations in the root are generally 20-30 times higher than that in the shoot, the P concentrations in the root are 1.5-2 times higher than that in the shoot, especially under the arsenic stress conditions. The AM fungus may have been highly tolerant to As and conferred tolerance to As on the plant by enhancing plant P nutrition and restricting root As uptake.