Effects Of Bt Transgenic Rice On Soil Ecosystem

This paper was supported by National Natural Science Foundation of China (Grant No. 30570226). The effects of Bt transgenic rice on community structure of soil fauna and microorganisms were studied from macro aspect by systemically investigation. The amplified fragment length poly- morphism (AFLP) reaction system was firstly used to investigate the effects of Bt transgenic rice on Enchytraeidae from micro aspect. A series of laboratory and field experiments were carried out, in order to systematically evaluate the biosafety effects of Bt transgenic rice on soil ecosystem.1 Effects of Bt transgenic rice on the community diversity of soil faunaSoil animals were investigated systematically in Bt transgenic rice and non-Bt transgenic rice. A total of 7798 specimens were collected, belonging to 3 phyla, 6 classes, and 11 orders. Dorylaimida and Tylenchida were the dominant groups, and Tubificida was the frequent one. There was no significant differences in community density, group richness, Shannon-Wiener index of species diversity, Pielou index of evenness, Simpson index of dominance and density-group index between Bt transgenic rice and non-Bt transgenic rice (P>0.05 ). The impact of Bt transgenic rice on the stability of community structure was not obvious. The density and percentage of Tubificida, Acarina, Collembola and Harpacticoida were higher in non-Bt transgenic rice field than Bt transgenic rice field and decreased gradely from non-Bt transgenic rice to Bt transgenic rice. It showed there was a negative effect of Bt transgenic rice on density and frequency of soil fauna. Bt toxic protein may had effect on heath of individuals of soil fauna.2 Effects of transgenic Bt rice on the community diversity of soil microorganismsThe results showed that there was significant difference between the groups and amounts of culturable bacteria, actinomyces , moulds and yeasts in soil of Bt transgenic rice and corresponding non-Bt transgenic rice. The same species were only eight. The numbers of bacteria and yeasts decreased, while that of actinomyces and moulds increased in the Bt transgenic rice field. There was significant difference between the Shannon-Wiener index and Pielou index in soil of Bt transgenic rice and corresponding non-Bt transgenic rice (P<0.05). It showed that there was significant effect of transgenic Bt rice on microorganisms diversity. It made a negative effect on bacteria and yeasts , while a active effect on actinomyces and moulds.3 AFLP analysis on Enchytraeidae in transgenic Bt rice and non-Bt rice fieldA total of 10 selective primer pairs amplified 1173 clear bands, and the mean amplied bands were 117.3. The amplified bands of Enchytraeidae from transgenic Bt rice field and non-Bt rice field were 578 and 595, respectively. The differentiation was not significant (P> 0.05). 377 polymorphic bands were amplified .The polymorphic bands of Enchytraeidae from non-Bt rice field and transgenic Bt rice field were 197 and 181, respectively. The percentage of polymorphic bands was 48.65%. There were significant differentiation between numbers and polymorphic ratio of band amplified by different primer combinations in Enchytraeidae from non-Bt rice field and transgenic Bt rice field. The molecular weight range of the polymorphic fragments was mainly 100-300 bp and the percentage was 68.02% and 71.82% in transgenic Bt rice field and non-Bt rice field, respectively. The Nei genetic similarities were 0.6786 and genetic distance was 0.3214 between Enchytraeidae from transgenic Bt rice field and non-Bt rice field . The results indicated that there were some molecular-level differentiation between Enchytraeidae from transgenic Bt rice field and non-Bt rice field. It indicated that there was significant effect of transgenic Bt rice on DNA polymorphism of Enchytraeidae.4 Analysis on the 16S rDNA gene of bacteria in Bt transgenic rice by Denaturing Gradient Gel ElectrophoresisThe molecular weight range of amplified 16S rDNA fragments was 400-450bp in in transgenic Bt rice field and non-Bt rice field. It was the specific fragments of V6-V9 region of 16S rDNA in bacteria. There were 10 dominant species in non-Bt rice field, while 15 in transgenic Bt rice field. Among them, only two common species existed in two rice fields and others were different species. The result indicated there was significant effect of transgenic Bt rice on bacteria compositions.