Effect Of Vegetation Of Transgenic Bt Rice And Its Straw Amendment On Soil Enzymes, Respiration, Functional And Structural Diversity Of Soil Microorganisms Under Field Conditions

With the development of transgenic crops, there is an increasing concern about the possible adverse effects of their vegetation and residues on soil environmental quality. To evaluate the effect of vegetation of transgenic Bt rice followed by return of rice straw on microbe-mediated functions in soil under field conditions, two Bt transgenic rice lines, Huachi B6 (Bt-HC) and TT51 (Bt-T), were adopted to assess the possible effect on soil enzyme (neutral phosphatase, urease, catalase, and invertase) activities, soil anaerobic respiration activity, and soil microbial community structure and functional diversity. Non-transgenic parental lines [Jiazao 935(P-JZ) and Minghui 63 (P-MH)] and distant parental rice varieties [Zhongjiu B (DP-ZJ) and 9311 (DP-9311)] were used as the controls. The results were summarized as follows:1. The activity of catalase was assayed by the KMnO4 titrimetric method, and activities of neutral phosphatase, urease and invertase were measured by colorimetry. The results indicated that the vegetation and straw addition of the two transgenic rice lines (Huachi B6 and TT51) have few adverse effect on soil enzymes, compared with their parent and distant parent, although some transient or even significant differences were observed. And there were also some significant differences between parental and distant parental rice.2. The evolution of CO2 from soil anaerobic respiration was analyzed by substrate induced method. The results demonstrated that cultivation of Bt-transgenic rice and addition of their straw have no persistent and adverse effect on soil anaerobic respiration activity.3. The functional diversity of soil microbial communities was assessed using Biolog ECO microplates. There were no significant difference between Bt, parent and distant parent in the AWCD, richness, and evenness of soil microorganisms. The dominant population of soil microbial communities seemed to be more sensitive and was altered temporarily by vegetation and straw amendment of Bt rice. This alteration is, however, smaller than that caused by vegetation and straw amendment of non-transgenic distant parental rice. 4. Soil microbial community structure was analyzed using 16S rDNA-based PCR-TGGE. There were no different bands between Bt and non-Bt in TGGE gel, but some brightness differences were detected. By recovery, cloning and sequence analysis, these bands with brightness differences may probably belong to Proteobacteria, Actinobacteria, Clostridia, and Anaerolineae.