Genetic Diversity Of Lysimachia Clethroides Populations In The Lead-zinc Mine Tailings And The Diversity Of Soil Microbial Community

With high content of heavy metals and low content of nutrition of lead-zinc mine tailing, the lead-zinc mine tailings provides a special environment for plants and soil microbes. In order to explore the impact of the lead-zinc mine tailings on the the genetic differentiation of Lysimachia dethroides population aboveground and the diverstiy of soil microbial community underground, the genetic diversity and genetic differentiation of Lysimachia dethroides population on Pd-Zn mine tailing with different exposed time was analyed by random amplified polymorphic (RAPD) technique, the bacteria numbers in rhizosphere and non-rhizosphere soil of Erigeron annuus, Equisctum ramosissimum, Pueraria lobata, Imperata cylindrica, Lysimachia dethroides which were distributed wide on the lead-zinc mine tailing was counted using acridine orange direct counts technique and the diversity of soil microbial communities in them were analyzed by Biolog and DGGE techniques.The results were showed as the following.1. The genetic diversity and differentiation of Lysimachia dethroides from DZ population (population form control soil), ES population (population from lead-zinc mine tailing which exposed 20 years) and YS population (population from lead-zinc mine tailing which exposed 10 years) above the lead-zinc mine tailings were analyzed using RAPD technique. Using 12 random primers, 157 repetitive loci were produced in 60 individual of Lysimachia dethroides, among which 92 loci were ploymorphic. The total percentage of polymorphic loci (p) of Lysimachia dethroides was 58.60%, which was relatively high. The genetic diversity ranked in the decreased order: ES populatons, DZ population and YS population with an average 44.16%. The total genetic diversity estimated by Shannon information index (I) was 0.3123 with an average 0.2530 and that estimated by Nei index (h) was 0.2086 with an average 0.1726. Jurdged by I and h, the genetic diversity of DZ population ranked first, followed by ES population, and then YS population. The differences of genetic diversity between 3 populations might be due to the loass of the heavy metal sensitive gene and fixation of the heavy metal torlerant gene. AMOVA results showed that 21.67% variation exsited among populations while 78.33% variation existed between populations, indicating that there was relatively high genetic differentiation among populations. The gene flow (N_m) was 2.3957. The genetic distance between two populations above lead-zinc mine talings was the least, while the genetic distance between populations above lead-zinc talings and control population was relatively large, suggesting that the heavy pollution might-be a main reason in the differentiation of Lysimachia dethroides.2. The concentration of heavy metal in the lead-zinc mine tailings was ranked in the decreased order, Pb, Zn, Cu, Co and Cd. The total and available heavy metal concentration of lead-zinc mine tailings were evidently higher than control soil, but the total number of culturable bacteria in lead-zinc mine tailings was significantly lower than that in the control soil. The heavy metal torlerant bacteria could be detected in lead-zinc mine talings and control soil and that in lead-zinc mine tailings was relatively high. The plasmid occurance of Pb-resistant was 93.1% and 90.3% in lead-zinc mine tailing and in control soil, respectively. The plasmid incidence of Zn-resistant was 74.07% and 70.59% in lead-zinc mine tailing and in control soil, respectively.3. The rhizosphere soils of five different plants were a bit better than non-rhizosphere soils, regarding the concentration of organic C and the total N. But regarding the concentration of available heavy metals (Pb,Zn,Cu,Cd), the rhizosphere soils of Erigeron, annuus, Imperata cylindrica, Putraria Iobaia were higher than non-rhizosphere soils. Regarding the bacteria number, the rhizosphere soils were higher than non-rhizosphere soils with significant different in Equisetum ramosissimum. The average well color development (AWCD), Shannon-Wiener index, Simpson index and Evelines indices of microbial community in rhizosphere soil of Erigeron annuus, Putraria Iobaia, Lysimachia clethroides were higher than those in non-rhizosphere soil, except Imperata cylindrica and Equisctum ramosissimum. The urease andβ-D-glucosidase activities in rhizosphere soil were higher than those in non-rhizosphere soils which was significant different except that of Erigeron annuus, while there was no difference of the phosphotase activity of Imperata cylindrical between rhizosphere soil and non-rhizosphere soil. This indicated that the carbon utilization ability and the soil enzyme activities in rhizosphere soil were higher than those in non-rhizosphere soil.4. The diversity of soil microbial communities in rhizosphere soil and non-rhizosphere soil of five plants were analyzed using denaturing gradient gel electrophoreses (DGGE) Technique. The 16SrRNA gene(V₃ region) were amplified by using the general primers (F₃₃₈ and R₅₁₈) and the results of agarose gel (1.6%) electrophoresis showed that the PCR products were about 200 bp. The amplified DNA fragments were then separated by DGGE and the result showed that there was some difference between th microbial community in rhizosphere and non-rhizozphere soil. As a whole, the microbial diversity of rhizosphere soils are higher than the non-rhizosphere soils. The difference might be due to the micro-environments in the rhizosphere and non-rhizosphere environments which changed with plants.