Effects of chitinase-transgenic (McChit1) tobacco on the rhizospheric microflora and enzyme activities of the purple soil

In order to evaluate the bio-security of genetically modified (GM) plants in the purple soil, we carried out a pot experiment about rhizospheric microflora at different development stages of a chitinase-transgenic (McChit1) tobacco (T-Chit), a plasmid-transgenic tobacco (T-Vi), and a non-transgenic tobacco (Nt-X) that were grown in the same purple soil, and surveyed the growth of three tobaccos and the properties of soil (i.e. the dynamic changes of the cultivable rhizospheric bacteria and fungi, soil enzyme activity and pH). The results showed that, compared with Nt-X plant as a control, T-Chit and T-Vi at the stages of flowering and mature significantly decreased the number of cultivable rhizospheric bacteria, but at their stubble stage the bacteria number returned to the same levels. Moreover, there were no significant differences about the number of cultivable rhizospheric fungi and the ratio of fungi to bacteria (F/B) among three treatments. It was of interest that soil catalase activities of T-Chit and T-Vi were lower than that of Nt-X during the same period, and urease activities of T-Vi and T-Chit were also lower than that of Nt-X at the stages of budding and stubble. Protease activity and the biomass of tobacco, however, showed no significant difference. This indicated that 1-year-old transgenic tobacco plants (T-Vi and T-Chit) inhibited the catalase and urease activities of the purple soil. In conclusion, the results revealed that 1-year-old T-Chit and T-Vi plants were non-toxic to the colony-forming units of cultivable bacteria and fungi in the studied purple soil during tobacco growth.