| At present, the research of domestic and foreign scholars on the transgenic plants is mainly concentrated in the effects of transgenic plants on soil biological population, functional groups and soil biodiversity and soil ecology process, the study on the mechanism of disease resistance and nutrient content is less, and the main research is on genetically modified crops rhizosphere environment in no external microorganisms.But GM crops in the planting process are inevitably infected by external microorganism, for this case, it is important for research on the growth and effects on the rhizosphere environment of genetically modified crops.In this pot experiment, tobacco was taken as the model plant, purple soil as tested soil and non-transgenic tobacco (Nt-X) as the control. Fungal biocontrol Trichoderma, fungal pathogen Verticillium dahliae and non inoculated treatment were respectively inoculated into the rhizosphere of the plants. This experiment preliminary discusses the effects of two types of fungi on growth and rhizosphere environment of Chitinase Gene Transformation of tobacco (T-Chit). The main contents of the research included:after inoculating Trichoderma and Verticillium dahliae respectively, the effects of defensing enzyme activities and nutrient content of T-Chit plant, the changes of rhizosphere soil enzyme, dynamic changes of soil microbial quantity, physicochemical properties and bacterial community structure in rhizosphere soil after60days of T-Chit.This research was mainly to explore the impact of the growth and rhizosphere environment of the transgenic tobacco and provide the comprehensive theoretical basis for ecological safety of genetically modified crops from two different types of fungi infection. The results are as follows:(1)With inoculation of Trichoderma, PAL and POD of T-Chit were significantly increased than that of control, which was consistent with the performance of Nt-X. At this time, the activities of PAL and POD of the chitinase-transgenic tobacco were significantly higher than that of the wild type tobacco. On the growth of plants, there was no significant difference on biomass in both root and shoot of T-Chit inoculated with Trichoderma, which was consistent with the Nt-X. So as the biomass of two strains of tobacco. And Trichoderma treatment, It improved the utilization rate of K in the root systerm of T-Chit and also the N and K of Nt-X when the tobacco was inoculated with trichoderma. At this time, there was no significant difference of the content of N and P between chitinase-transgenic tobacco and wild type tobacco, but the content of K of the latter root was significantly higher than that of the former.(2)After inoculated with Trichoderma, change trend of rhizosphere soil enzyme activity in T-Chit and Nt-X was the same, but it had differences after inoculation.60days later, there had no significant difference on activity of catalase, urease and invertase of rhizosphere soil between the two plants.But the pH of rhizosphere soil and the content of total K of T-Chit were significantly higher than that of Nt-X which indicated that acidification of rhizosphere soil of T-Chit was low which was less harmful to soil. Organic matter, total N and total P of two strains of tobacco had no significant difference.(3)With inoculation of Trichoderma, the quantity of culturable microorganisms changed to some extent, but the change trend of T-Chit and Nt-X was basically the same. But on the sixtieth day, the count of bacteria in the rhizosphere soil of T-Chit was higher than Nt-X, the number of fungi in the rhizosphere soil was significantly lower than those in Nt-X, and there was no significant difference on the number of actinomycetes in the rhizosphere soil of Nt-X. This showed that the change from "bacterial type" to "fungi type" of T-Chit rhizosphere soil was slowly and the biological activity of rhizosphere was higher than Nt-X when colonization with Trichoderma. The similarity index of bacterial community structure in two strains of tobacco which was inoculated with Trichoderma was higher, so it indicated that the effect on bacterial community structure in rhizosphere soil of T-Chit and wild type tobacco was basically consistent with inoculation with Trichoderma.(4)Because of induced resistance of Verticillium dahliae on plants, PAL and POD activity of T-Chit which was inoculated with Verticillium dahliae also had different degrees of increase that was consistent with the change trend of Nt-X. But the PAL and POD activity of two genotypes tobacco had no significant difference, which may be due to the different emergency response duration of two genotypes tobacco. There was no significant difference on biomass of T-Chit and Nt-X between inoculated with Verticillium dahliae and not vaccinated, so as between the two strains of tobacco.It was significantly increased the content of K in T-Chit root only and P in Nt-X root. At this time,the shoot nutrient (N, P, K) content of T-Chit and Nt-X had no significant difference, but the content of P of the former was17.2%that was lower than the latter.(5)The change trend of rhizosphere soil enzyme activity of T-Chit and Nt-X was basically the same after inoculated with Verticillium dahliae,but the change extent was different. Catalase activity of all tobacco rhizosphere soil in two strains had a significantly lower process, after60days, there was no significant difference on compared with no inoculation, but at this point, the catalase content of rhizosphere soil in T-Chit was significantly lower than in Nt-X. Urease activity of rhizosphere soil had no significant difference between T-Chit and Nt-X in each sampling period after vaccinated. In45th day and60th day, invertase content of rhizosphere soil in T-Chit was significantly lower than in Nt-X. After inoculated in60days, pH and content of total K of rhizospheric soil had no significant difference between two strains of tobacco. But organic matter and content of total N of rhizosphere soil in T-Chit were significantly higher than that in Nt-X. It showed that soil enzyme activity of T-Chit was decreased and metabolism was slowly after inoculated with Verticillium dahliae for60days,which was compared with the Nt-X, this is also an important reason of higher organic matter and total N content in the soil.(6) There was no significant difference on number of rhizosphere bacteria, actinomyces of the T-Chit and Nt-X in every sampling period after inoculated with Verticillium dahliae. On the60th day, the number of rhizosphere fungi in T-Chit was significantly less than in Nt-X, this may be related to excess expression of balsam pear chitinase gene inhibited the proliferation of the rhizosphere fungi after inoculation.It showed that it was basicly consistent of impact on bacterial community structure of rhizosphere soil on chitinase gene tobacco and the wild type tobacco when the similarity coefficient of two strains of tobacco with inoculation of Verticillium dahliae was higher.But bacterial community structure of root soil in the same strain tobacco with different processing had significant difference, which showed that inoculation of Verticillium dahliae affected the rhizosphere bacteria community structure of tobacco plant. |
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