Effect Of Disease-resistant Transgenic Tobacco And Continuous Cropping Cabbage On Micro-ecology Environment Of Plant Rhizosphere Soil

In this study,we analyzed the number of cultivable microorganisms,bacterial community diversity,enzyme activity and physicochemical property of soil samples of transgenic Psc-AFP(T-PA),transgenic LJAMP2(T-Lj),wild type(WT)and transgenic control vector(T-Vi)tobacco respectively.At the same time,we discussed the variation of microbial communities around 2-,10-,and 15-year continuous cropping-Cabbage.The results listed as follows:Part 1 Influence of transgenic tobacco on micro-ecology of rhizosphere soil1.Influence of disease-resistant transgenic tobacco on cultivable microorganisms,soil enzyme activity and physicochemical properties of rhizosphere soil(1)Influence of disease-resistant transgenic tobacco on cultivable microorganismsThe number of cultivable bacteria,fungi and actinomycetes changed with the growth and development of tobacco,and reached the highest peak at the period of vigorous growth or mature stage.however,at the same period,the number of cultivable microorganisms were different among different types of tobacco.Except mature stage,the number of bacteria,fungi and actinomycetes between T-PA and WT tobacco was not significantly different(P<0.05),and the number of cultivable microorganisms between T-Lj and WT tobacco was significantly different(P<0.05)during the period of vigorous growth,whereas during the three other periods is not the results demonstrated that the plantation of T-PA and T-Lj tobacco had affected the number of cultivable rhizosphere microorganisms,and the influence varied along with different growth stages.(2)Influence of T-PA tobacco on soil enzyme activityThe activity of catalase,urease,sucrase and alkaline phosphatase changed with the growing period of the three types of tobacco,and the variation trends were almost the same.The activities of catalase,sucrase and alkaline phosphatase were not significantly different during the same growing period which indicated that T-PA tobacco had little effect on them.However,the activity of urease was significantly different in three former periods except the mature period,which indicated that the effect on urease was not sustained.(3)Influence of T-PA tobacco on soil physicochemical propertiesThrough the analysis of soil physicochemical property of seeding and mature period the values of pH,organic matter,total nitrogen,total phosphorus and total potassium of T-PA tobacco were significantly higher than WT and T-Vi tobacco.And the change in physicochemical property of T-PA tobacco was also greater than WT and T-Vi tobacco.2.Influence of disease-resistant transgenic tobacco on bacterial community diversity of rhizosphere soil(1)Influence of T-PA tobacco on bacterial community diversity of rhizosphere soilWe using PCR-DGGE analyzed the bacterial community diversity of T-PA,WT and T-Vi tobacco,and the results showed that the species of soil bacteria were rich in each period.Analysis of DGGE profiles in all the periods showed that number of bands,diversity index and evenness were not significantly different(p<0.05).Cluster analysis showed that the soil bacterial community of T-PA and WT was highly similar at the same growth period.All the values indicated that the influence of T-PA tobacco on soil bacterial diversity was not significant.(1)Influence of T-Lj tobacco on bacterial community diversity of rhizosphere soilAnalysis of PCR-SSCP profiles showed that T-Lj tobacco had some influence on soil microbial community structure.However,we can't assure whether the effect was sustained,and it requires further study.Part 2 Effect of continuous cropping cabbage on soil micro-ecologyThe results showed that cabbage continuous cropping had great effect on these four aspects.With the year of continuous cropping increasing,the number of culturable bacteria showed the trend of declining-rising-declining,and when after 15 years of continuous cropping,the bacteria in replant soil decreased significantly by 31.7%compared with the control.Number of culturable fungi showed a trend of increased initially and then decreased,and reached the highest after 2 years of continuous cropping by increasing by 72.2%compared with the control.The number of culturable actinomycetes was significantly lower than that in control soil in different years and in the 15th year,it decreased by 55.6%compared with the control.The soil bacterial species were not all the same in different years.Comparing with the control,there was a certain acidification trend in replant soil.Till the 15-year,the soil pH returned to a slightly higher level than control.In addition,total potassium,alkaline hydrolysis nitrogen,available phosphorus and available potassium highly enriched in replant soil at different degrees.Catalase activity and urease activity of replant soil were lower than that of control significantly in the 10-and 15-year,resulting in the accumulation of hydrogen peroxide,reduction of soil nitrogen levels and continuous cropping obstacle.Through denaturing gradient gel electrophoresis(DGGE),clone and sequence,we analysed the bacterial community structure in soil,and demonstrated that the vegetables planting period length had impact on the community structure,the influence was related with continuous cropping years.At the meantime,we also demonstrated that group of bacteria was mainly Poteobacteria sp.Sphingobacteria sp.and Acidobacteria sp.were also discoveried.