The Study Of Microbial Diversity In Rhizosphere Of Soybean After Treatment With Seed Coatings

This experiment studied the dynamic of microorganisms and the genetic diversity ofmicrobial community in soybean rhizosphere with dilution method and DGGE, after treatmentwith different concentrations of Metalaxyl, Carbofuran-Carbendazim-Thiram, Ningnanmycinand Fludioxonil. We gained the changes and differences of the amount of microorganisms andgenetic diversity, and analyzed the factors that influence the rhizosphere microbial community,and tried to provide scientific bases for using pesticide, which will improve plant yield andquality.The main conclusions of this paper were as follows:1. Metalaxyl and Carbofuran-Carbendazim-Thiram increased the amount of soybeanrhizosphere microorganisms from 0.81% to 178.54%. The amount of microorganisms increasedby 178.54% after treatment with the middle concentration of Metalaxyl, and its stimulativeaction was the strongest; the second one was the low concentration ofCarbofuran-Carbendazim-Thiram, and the amount of microorganisms increased by 102.91%; theweakest one was the high concentration of Carbofuran-Carbendazim-Thiram, and the amount ofmicroorganisms increased by 0.81%. Different concentrations of Ningnanmycin and Fludioxonilhad different effects on soybean rhizospheric microorganisms. The high concentration andmiddle concentration of Ningnanmycin and Fludioxonil inhibited and the low concentration ofNingnanmycin and Fludioxonil promoted the multiplication of rhizospheric microorganisms.2. At the early period, the four kinds of seed coatings all increased the amount of soybeanrhizospheric fungi and actinomycetes, and decreased the amount of rhizospheric azotobacteriaand root nodules, then the effects recovered to the normal level at the later period.3. The four kinds of seed coatings all affected the genetic diversity of soybean rhizosphericbacteria. At the early period, Ningnanmycin and Fludioxonil raised and Metalaxy andCarbofuran-Carbendazim-Thiram reduced the genetic diversity index. The effects recovered tothe normal level at the later period. The heredities of soybean rhizospheric bacteria were similarafter treatment with three concentrations of the same seed coating. At the 22nd day, all the treatments affected the community of soybean rhizospheric bacteria. At the 60th day, the effectsevanesced, and the treatment of Ningnanmycin recovered fastest.